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Diffstat (limited to 'documentation/kernel-dev')
17 files changed, 715 insertions, 7654 deletions
diff --git a/documentation/kernel-dev/kernel-dev-advanced.rst b/documentation/kernel-dev/advanced.rst index 36133caae3..4c463503f6 100644 --- a/documentation/kernel-dev/kernel-dev-advanced.rst +++ b/documentation/kernel-dev/advanced.rst @@ -1,11 +1,9 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ******************************************************* Working with Advanced Metadata (``yocto-kernel-cache``) ******************************************************* -.. _kernel-dev-advanced-overview: - Overview ======== @@ -18,12 +16,12 @@ complexity of the configuration and sources used to support multiple BSPs and Linux kernel types. Kernel Metadata exists in many places. One area in the -:ref:`overview-manual/overview-manual-development-environment:yocto project source repositories` +:ref:`overview-manual/development-environment:yocto project source repositories` is the ``yocto-kernel-cache`` Git repository. You can find this repository grouped under the "Yocto Linux Kernel" heading in the :yocto_git:`Yocto Project Source Repositories <>`. -Kernel development tools ("kern-tools") exist also in the Yocto Project +Kernel development tools ("kern-tools") are also available in the Yocto Project Source Repositories under the "Yocto Linux Kernel" heading in the ``yocto-kernel-tools`` Git repository. The recipe that builds these tools is ``meta/recipes-kernel/kern-tools/kern-tools-native_git.bb`` in @@ -44,24 +42,22 @@ linux-yocto recipe. .. note:: A Linux kernel recipe that contains kernel Metadata (e.g. inherits - from the - linux-yocto.inc - file) is said to be a "linux-yocto style" recipe. + from the ``linux-yocto.inc`` file) is said to be a "linux-yocto style" recipe. Every linux-yocto style recipe must define the :term:`KMACHINE` variable. This -variable is typically set to the same value as the ``MACHINE`` variable, +variable is typically set to the same value as the :term:`MACHINE` variable, which is used by :term:`BitBake`. However, in some cases, the variable might instead refer to the -underlying platform of the ``MACHINE``. +underlying platform of the :term:`MACHINE`. -Multiple BSPs can reuse the same ``KMACHINE`` name if they are built +Multiple BSPs can reuse the same :term:`KMACHINE` name if they are built using the same BSP description. Multiple Corei7-based BSPs could share -the same "intel-corei7-64" value for ``KMACHINE``. It is important to -realize that ``KMACHINE`` is just for kernel mapping, while ``MACHINE`` +the same "intel-corei7-64" value for :term:`KMACHINE`. It is important to +realize that :term:`KMACHINE` is just for kernel mapping, while :term:`MACHINE` is the machine type within a BSP Layer. Even with this distinction, -however, these two variables can hold the same value. See the `BSP -Descriptions <#bsp-descriptions>`__ section for more information. +however, these two variables can hold the same value. See the +":ref:`kernel-dev/advanced:bsp descriptions`" section for more information. Every linux-yocto style recipe must also indicate the Linux kernel source repository branch used to build the Linux kernel. The @@ -70,16 +66,10 @@ to indicate the branch. .. note:: - You can use the - KBRANCH - value to define an alternate branch typically with a machine override - as shown here from the - meta-yocto-bsp - layer: - :: - - KBRANCH_edgerouter = "standard/edgerouter" + You can use the :term:`KBRANCH` value to define an alternate branch typically + with a machine override as shown here from the ``meta-yocto-bsp`` layer:: + KBRANCH:beaglebone-yocto = "standard/beaglebone" The linux-yocto style recipes can optionally define the following variables: @@ -90,49 +80,47 @@ variables: :term:`LINUX_KERNEL_TYPE` defines the kernel type to be used in assembling the configuration. If -you do not specify a ``LINUX_KERNEL_TYPE``, it defaults to "standard". -Together with ``KMACHINE``, ``LINUX_KERNEL_TYPE`` defines the search +you do not specify a :term:`LINUX_KERNEL_TYPE`, it defaults to "standard". +Together with :term:`KMACHINE`, :term:`LINUX_KERNEL_TYPE` defines the search arguments used by the kernel tools to find the appropriate description within the kernel Metadata with which to build out the sources and configuration. The linux-yocto recipes define "standard", "tiny", and -"preempt-rt" kernel types. See the "`Kernel Types <#kernel-types>`__" +"preempt-rt" kernel types. See the ":ref:`kernel-dev/advanced:kernel types`" section for more information on kernel types. During the build, the kern-tools search for the BSP description file -that most closely matches the ``KMACHINE`` and ``LINUX_KERNEL_TYPE`` +that most closely matches the :term:`KMACHINE` and :term:`LINUX_KERNEL_TYPE` variables passed in from the recipe. The tools use the first BSP -description it finds that match both variables. If the tools cannot find +description they find that matches both variables. If the tools cannot find a match, they issue a warning. -The tools first search for the ``KMACHINE`` and then for the -``LINUX_KERNEL_TYPE``. If the tools cannot find a partial match, they -will use the sources from the ``KBRANCH`` and any configuration +The tools first search for the :term:`KMACHINE` and then for the +:term:`LINUX_KERNEL_TYPE`. If the tools cannot find a partial match, they +will use the sources from the :term:`KBRANCH` and any configuration specified in the :term:`SRC_URI`. You can use the :term:`KERNEL_FEATURES` variable to include features (configuration fragments, patches, or both) -that are not already included by the ``KMACHINE`` and -``LINUX_KERNEL_TYPE`` variable combination. For example, to include a -feature specified as "features/netfilter/netfilter.scc", specify: -:: +that are not already included by the :term:`KMACHINE` and +:term:`LINUX_KERNEL_TYPE` variable combination. For example, to include a +feature specified as "features/netfilter/netfilter.scc", specify:: KERNEL_FEATURES += "features/netfilter/netfilter.scc" To include a feature called "cfg/sound.scc" just for the ``qemux86`` machine, -specify: -:: +specify:: - KERNEL_FEATURES_append_qemux86 = " cfg/sound.scc" + KERNEL_FEATURES:append:qemux86 = " cfg/sound.scc" The value of -the entries in ``KERNEL_FEATURES`` are dependent on their location +the entries in :term:`KERNEL_FEATURES` are dependent on their location within the kernel Metadata itself. The examples here are taken from the ``yocto-kernel-cache`` repository. Each branch of this repository contains "features" and "cfg" subdirectories at the top-level. For more -information, see the "`Kernel Metadata -Syntax <#kernel-metadata-syntax>`__" section. +information, see the ":ref:`kernel-dev/advanced:kernel metadata syntax`" +section. Kernel Metadata Syntax ====================== @@ -156,7 +144,7 @@ Features aggregate sources in the form of patches and configuration fragments into a modular reusable unit. You can use features to implement conceptually separate kernel Metadata descriptions such as pure configuration fragments, simple patches, complex features, and -kernel types. `Kernel types <#kernel-types>`__ define general kernel +kernel types. :ref:`kernel-dev/advanced:kernel types` define general kernel features and policy to be reused in the BSPs. BSPs define hardware-specific features and aggregate them with kernel @@ -165,8 +153,7 @@ types to form the final description of what will be assembled and built. While the kernel Metadata syntax does not enforce any logical separation of configuration fragments, patches, features or kernel types, best practices dictate a logical separation of these types of Metadata. The -following Metadata file hierarchy is recommended: -:: +following Metadata file hierarchy is recommended:: base/ bsp/ @@ -175,10 +162,9 @@ following Metadata file hierarchy is recommended: ktypes/ patches/ -The ``bsp`` directory contains the `BSP -descriptions <#bsp-descriptions>`__. The remaining directories all -contain "features". Separating ``bsp`` from the rest of the structure -aids conceptualizing intended usage. +The ``bsp`` directory contains the :ref:`kernel-dev/advanced:bsp descriptions`. +The remaining directories all contain "features". Separating ``bsp`` from the +rest of the structure aids conceptualizing intended usage. Use these guidelines to help place your ``scc`` description files within the structure: @@ -196,7 +182,7 @@ the structure: order to define a base kernel policy or major kernel type to be reused across multiple BSPs, place the file in ``ktypes`` directory. -These distinctions can easily become blurred - especially as out-of-tree +These distinctions can easily become blurred --- especially as out-of-tree features slowly merge upstream over time. Also, remember that how the description files are placed is a purely logical organization and has no impact on the functionality of the kernel Metadata. There is no impact @@ -206,11 +192,12 @@ contain "features" as far as the kernel tools are concerned. Paths used in kernel Metadata files are relative to base, which is either :term:`FILESEXTRAPATHS` if -you are creating Metadata in `recipe-space <#recipe-space-metadata>`__, +you are creating Metadata in +:ref:`recipe-space <kernel-dev/advanced:recipe-space metadata>`, or the top level of -:yocto_git:`yocto-kernel-cache </cgit/cgit.cgi/yocto-kernel-cache/tree/>` -if you are creating `Metadata outside of the -recipe-space <#metadata-outside-the-recipe-space>`__. +:yocto_git:`yocto-kernel-cache </yocto-kernel-cache/tree/>` +if you are creating +:ref:`kernel-dev/advanced:metadata outside the recipe-space`. .. [1] ``scc`` stands for Series Configuration Control, but the naming has @@ -230,8 +217,7 @@ used with the ``linux-yocto-4.12`` kernel as defined outside of the recipe space (i.e. ``yocto-kernel-cache``). This Metadata consists of two files: ``smp.scc`` and ``smp.cfg``. You can find these files in the ``cfg`` directory of the ``yocto-4.12`` branch in the -``yocto-kernel-cache`` Git repository: -:: +``yocto-kernel-cache`` Git repository:: cfg/smp.scc: define KFEATURE_DESCRIPTION "Enable SMP for 32 bit builds" @@ -251,8 +237,7 @@ two files: ``smp.scc`` and ``smp.cfg``. You can find these files in the CONFIG_X86_BIGSMP=y You can find general information on configuration -fragment files in the "`Creating Configuration -Fragments <#creating-config-fragments>`__" section. +fragment files in the ":ref:`kernel-dev/common:creating configuration fragments`" section. Within the ``smp.scc`` file, the :term:`KFEATURE_DESCRIPTION` @@ -269,14 +254,12 @@ non-hardware fragment. .. note:: - The description file can include multiple - kconf - statements, one per fragment. + The description file can include multiple ``kconf`` statements, one per + fragment. -As described in the "`Validating -Configuration <#validating-configuration>`__" section, you can use the -following BitBake command to audit your configuration: -:: +As described in the +":ref:`kernel-dev/common:validating configuration`" section, you can +use the following BitBake command to audit your configuration:: $ bitbake linux-yocto -c kernel_configcheck -f @@ -297,8 +280,7 @@ in the ``patches/build`` directory of the ``yocto-4.12`` branch in the ``yocto-kernel-cache`` Git repository. The following listings show the ``build.scc`` file and part of the -``modpost-mask-trivial-warnings.patch`` file: -:: +``modpost-mask-trivial-warnings.patch`` file:: patches/build/build.scc: patch arm-serialize-build-targets.patch @@ -321,8 +303,8 @@ The following listings show the ``build.scc`` file and part of the . . . - char *dump_write = NULL, *files_source = NULL; - int opt; + char *dump_write = NULL, *files_source = NULL; + int opt; -- 2.10.1 @@ -330,15 +312,13 @@ The following listings show the ``build.scc`` file and part of the The description file can include multiple patch statements where each statement handles a single -patch. In the example ``build.scc`` file, five patch statements exist +patch. In the example ``build.scc`` file, there are five patch statements for the five patches in the directory. You can create a typical ``.patch`` file using ``diff -Nurp`` or ``git format-patch`` commands. For information on how to create patches, -see the "`Using ``devtool`` to Patch the -Kernel <#using-devtool-to-patch-the-kernel>`__" and "`Using Traditional -Kernel Development to Patch the -Kernel <#using-traditional-kernel-development-to-patch-the-kernel>`__" +see the ":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" +and ":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" sections. Features @@ -346,8 +326,7 @@ Features Features are complex kernel Metadata types that consist of configuration fragments, patches, and possibly other feature description files. As an -example, consider the following generic listing: -:: +example, consider the following generic listing:: features/myfeature.scc define KFEATURE_DESCRIPTION "Enable myfeature" @@ -364,48 +343,40 @@ as how an additional feature description file is included with the Typically, features are less granular than configuration fragments and are more likely than configuration fragments and patches to be the types -of things you want to specify in the ``KERNEL_FEATURES`` variable of the -Linux kernel recipe. See the "`Using Kernel Metadata in a -Recipe <#using-kernel-metadata-in-a-recipe>`__" section earlier in the -manual. +of things you want to specify in the :term:`KERNEL_FEATURES` variable of the +Linux kernel recipe. See the +":ref:`kernel-dev/advanced:using kernel metadata in a recipe`" section earlier +in the manual. Kernel Types ------------ -A kernel type defines a high-level kernel policy by aggregating -non-hardware configuration fragments with patches you want to use when -building a Linux kernel of a specific type (e.g. a real-time kernel). -Syntactically, kernel types are no different than features as described -in the "`Features <#features>`__" section. The -:term:`LINUX_KERNEL_TYPE` -variable in the kernel recipe selects the kernel type. For example, in -the ``linux-yocto_4.12.bb`` kernel recipe found in -``poky/meta/recipes-kernel/linux``, a -:ref:`require <bitbake:require-inclusion>` directive -includes the ``poky/meta/recipes-kernel/linux/linux-yocto.inc`` file, -which has the following statement that defines the default kernel type: -:: +A kernel type defines a high-level kernel policy by aggregating non-hardware +configuration fragments with patches you want to use when building a Linux +kernel of a specific type (e.g. a real-time kernel). Syntactically, kernel +types are no different than features as described in the +":ref:`kernel-dev/advanced:features`" section. The :term:`LINUX_KERNEL_TYPE` +variable in the kernel recipe selects the kernel type. For example, in the +``linux-yocto_4.12.bb`` kernel recipe found in ``poky/meta/recipes-kernel/linux``, a +:ref:`require <bitbake-user-manual/bitbake-user-manual-metadata:\`\`require\`\` directive>` +directive includes the ``poky/meta/recipes-kernel/linux/linux-yocto.inc`` file, +which has the following statement that defines the default kernel type:: LINUX_KERNEL_TYPE ??= "standard" Another example would be the real-time kernel (i.e. ``linux-yocto-rt_4.12.bb``). This kernel recipe directly sets the kernel -type as follows: -:: +type as follows:: LINUX_KERNEL_TYPE = "preempt-rt" .. note:: - You can find kernel recipes in the - meta/recipes-kernel/linux - directory of the - Source Directory - (e.g. - poky/meta/recipes-kernel/linux/linux-yocto_4.12.bb - ). See the " - Using Kernel Metadata in a Recipe - " section for more information. + You can find kernel recipes in the ``meta/recipes-kernel/linux`` directory + of the :ref:`overview-manual/development-environment:yocto project source repositories` + (e.g. ``poky/meta/recipes-kernel/linux/linux-yocto_4.12.bb``). See the + ":ref:`kernel-dev/advanced:using kernel metadata in a recipe`" + section for more information. Three kernel types ("standard", "tiny", and "preempt-rt") are supported for Linux Yocto kernels: @@ -428,8 +399,7 @@ for Linux Yocto kernels: For any given kernel type, the Metadata is defined by the ``.scc`` (e.g. ``standard.scc``). Here is a partial listing for the ``standard.scc`` file, which is found in the ``ktypes/standard`` directory of the -``yocto-kernel-cache`` Git repository: -:: +``yocto-kernel-cache`` Git repository:: # Include this kernel type fragment to get the standard features and # configuration values. @@ -466,16 +436,11 @@ and ``patch`` commands, respectively. .. note:: - It is not strictly necessary to create a kernel type - .scc + It is not strictly necessary to create a kernel type ``.scc`` file. The Board Support Package (BSP) file can implicitly define the - kernel type using a - define - KTYPE - myktype - line. See the " - BSP Descriptions - " section for more information. + kernel type using a ``define`` :term:`KTYPE` ``myktype`` line. See the + ":ref:`kernel-dev/advanced:bsp descriptions`" section for more + information. BSP Descriptions ---------------- @@ -488,20 +453,14 @@ supported kernel type. .. note:: For BSPs supported by the Yocto Project, the BSP description files - are located in the - bsp - directory of the - yocto-kernel-cache + are located in the ``bsp`` directory of the ``yocto-kernel-cache`` repository organized under the "Yocto Linux Kernel" heading in the - Yocto Project Source Repositories - . + :yocto_git:`Yocto Project Source Repositories <>`. This section overviews the BSP description structure, the aggregation concepts, and presents a detailed example using a BSP supported by the Yocto Project (i.e. BeagleBone Board). For complete information on BSP -layer file hierarchy, see the :doc:`../bsp-guide/bsp-guide`. - -.. _bsp-description-file-overview: +layer file hierarchy, see the :doc:`/bsp-guide/index`. Description Overview ~~~~~~~~~~~~~~~~~~~~ @@ -509,15 +468,13 @@ Description Overview For simplicity, consider the following root BSP layer description files for the BeagleBone board. These files employ both a structure and naming convention for consistency. The naming convention for the file is as -follows: -:: +follows:: bsp_root_name-kernel_type.scc Here are some example root layer BSP filenames for the BeagleBone Board BSP, which is supported by the -Yocto Project: -:: +Yocto Project:: beaglebone-standard.scc beaglebone-preempt-rt.scc @@ -525,8 +482,7 @@ Yocto Project: Each file uses the root name (i.e "beaglebone") BSP name followed by the kernel type. -Examine the ``beaglebone-standard.scc`` file: -:: +Examine the ``beaglebone-standard.scc`` file:: define KMACHINE beaglebone define KTYPE standard @@ -550,51 +506,45 @@ description as meeting the criteria set by the recipe being built. This example supports the "beaglebone" machine for the "standard" kernel and the "arm" architecture. -Be aware that a hard link between the ``KTYPE`` variable and a kernel -type description file does not exist. Thus, if you do not have the +Be aware that there is no hard link between the :term:`KTYPE` variable and a kernel +type description file. Thus, if you do not have the kernel type defined in your kernel Metadata as it is here, you only need to ensure that the :term:`LINUX_KERNEL_TYPE` -variable in the kernel recipe and the ``KTYPE`` variable in the BSP +variable in the kernel recipe and the :term:`KTYPE` variable in the BSP description file match. To separate your kernel policy from your hardware configuration, you include a kernel type (``ktype``), such as "standard". In the previous -example, this is done using the following: -:: +example, this is done using the following:: include ktypes/standard/standard.scc This file aggregates all the configuration fragments, patches, and features that make up your standard kernel -policy. See the "`Kernel Types <#kernel-types>`__" section for more +policy. See the ":ref:`kernel-dev/advanced:kernel types`" section for more information. To aggregate common configurations and features specific to the kernel -for mybsp, use the following: -:: +for `mybsp`, use the following:: include mybsp.scc -You can see that in the BeagleBone example with the following: -:: +You can see that in the BeagleBone example with the following:: include beaglebone.scc For information on how to break a complete ``.config`` file into the various -configuration fragments, see the "`Creating Configuration -Fragments <#creating-config-fragments>`__" section. +configuration fragments, see the ":ref:`kernel-dev/common:creating configuration fragments`" section. Finally, if you have any configurations specific to the hardware that -are not in a ``*.scc`` file, you can include them as follows: -:: +are not in a ``*.scc`` file, you can include them as follows:: kconf hardware mybsp-extra.cfg The BeagleBone example does not include these types of configurations. However, the Malta 32-bit board does -("mti-malta32"). Here is the ``mti-malta32-le-standard.scc`` file: -:: +("mti-malta32"). Here is the ``mti-malta32-le-standard.scc`` file:: define KMACHINE mti-malta32-le define KMACHINE qemumipsel @@ -607,23 +557,13 @@ types of configurations. However, the Malta 32-bit board does include mti-malta32.scc kconf hardware mti-malta32-le.cfg -.. _bsp-description-file-example-minnow: - Example ~~~~~~~ Many real-world examples are more complex. Like any other ``.scc`` file, BSP descriptions can aggregate features. Consider the Minnow BSP definition given the ``linux-yocto-4.4`` branch of the -``yocto-kernel-cache`` (i.e. -``yocto-kernel-cache/bsp/minnow/minnow.scc``): - -.. note:: - - Although the Minnow Board BSP is unused, the Metadata remains and is - being used here just as an example. - -:: +``yocto-kernel-cache`` (i.e. ``yocto-kernel-cache/bsp/minnow/minnow.scc``):: include cfg/x86.scc include features/eg20t/eg20t.scc @@ -646,6 +586,11 @@ definition given the ``linux-yocto-4.4`` branch of the kconf hardware minnow.cfg kconf hardware minnow-dev.cfg +.. note:: + + Although the Minnow Board BSP is unused, the Metadata remains and is + being used here just as an example. + The ``minnow.scc`` description file includes a hardware configuration fragment (``minnow.cfg``) specific to the Minnow BSP as well as several more general configuration fragments and features enabling hardware @@ -653,8 +598,7 @@ found on the machine. This ``minnow.scc`` description file is then included in each of the three "minnow" description files for the supported kernel types (i.e. "standard", "preempt-rt", and "tiny"). Consider the "minnow" description for the "standard" kernel type (i.e. -``minnow-standard.scc``: -:: +``minnow-standard.scc``):: define KMACHINE minnow define KTYPE standard @@ -686,8 +630,7 @@ that defines all enabled hardware for the BSP that is common to all kernel types. Using this command significantly reduces duplication. Now consider the "minnow" description for the "tiny" kernel type (i.e. -``minnow-tiny.scc``): -:: +``minnow-tiny.scc``):: define KMACHINE minnow define KTYPE tiny @@ -708,7 +651,7 @@ Notice again the three critical variables: :term:`KMACHINE`, :term:`KTYPE`, and :term:`KARCH`. Of these variables, only -``KTYPE`` has changed to specify the "tiny" kernel type. +:term:`KTYPE` has changed to specify the "tiny" kernel type. Kernel Metadata Location ======================== @@ -725,8 +668,8 @@ others, the recipe-space method is recommended. This method is also a good approach if you are working with Linux kernel sources you do not control or if you just do not want to maintain a Linux kernel Git repository on your own. For partial information on how you can define -kernel Metadata in the recipe-space, see the "`Modifying an Existing -Recipe <#modifying-an-existing-recipe>`__" section. +kernel Metadata in the recipe-space, see the +":ref:`kernel-dev/common:modifying an existing recipe`" section. Conversely, if you are actively developing a kernel and are already maintaining a Linux kernel Git repository of your own, you might find it @@ -739,19 +682,17 @@ Recipe-Space Metadata --------------------- When stored in recipe-space, the kernel Metadata files reside in a -directory hierarchy below -:term:`FILESEXTRAPATHS`. For -a linux-yocto recipe or for a Linux kernel recipe derived by copying and -modifying -``oe-core/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb`` to -a recipe in your layer, ``FILESEXTRAPATHS`` is typically set to +directory hierarchy below :term:`FILESEXTRAPATHS`. For +a linux-yocto recipe or for a Linux kernel recipe derived by copying +:oe_git:`meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb +</openembedded-core/tree/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb>` +into your layer and modifying it, :term:`FILESEXTRAPATHS` is typically set to ``${``\ :term:`THISDIR`\ ``}/${``\ :term:`PN`\ ``}``. -See the "`Modifying an Existing -Recipe <#modifying-an-existing-recipe>`__" section for more information. +See the ":ref:`kernel-dev/common:modifying an existing recipe`" +section for more information. Here is an example that shows a trivial tree of kernel Metadata stored -in recipe-space within a BSP layer: -:: +in recipe-space within a BSP layer:: meta-my_bsp_layer/ `-- recipes-kernel @@ -770,14 +711,13 @@ and fetches any files referenced in the ``.scc`` files by the ``include``, ``patch``, or ``kconf`` commands. Because of this, it is necessary to bump the recipe :term:`PR` value when changing the content of files not explicitly listed in the -``SRC_URI``. +:term:`SRC_URI`. If the BSP description is in recipe space, you cannot simply list the -``*.scc`` in the ``SRC_URI`` statement. You need to use the following -form from your kernel append file: -:: +``*.scc`` in the :term:`SRC_URI` statement. You need to use the following +form from your kernel append file:: - SRC_URI_append_myplatform = " \ + SRC_URI:append:myplatform = " \ file://myplatform;type=kmeta;destsuffix=myplatform \ " @@ -788,37 +728,35 @@ When stored outside of the recipe-space, the kernel Metadata files reside in a separate repository. The OpenEmbedded build system adds the Metadata to the build as a "type=kmeta" repository through the :term:`SRC_URI` variable. As an -example, consider the following ``SRC_URI`` statement from the -``linux-yocto_4.12.bb`` kernel recipe: -:: - - SRC_URI = "git://git.yoctoproject.org/linux-yocto-4.12.git;name=machine;branch=${KBRANCH}; \ - git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-4.12;destsuffix=${KMETA}" +example, consider the following :term:`SRC_URI` statement from the +``linux-yocto_5.15.bb`` kernel recipe:: + SRC_URI = "git://git.yoctoproject.org/linux-yocto.git;name=machine;branch=${KBRANCH};protocol=https \ + git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-5.15;destsuffix=${KMETA};protocol=https" ``${KMETA}``, in this context, is simply used to name the directory into which the Git fetcher places the Metadata. This behavior is no different -than any multi-repository ``SRC_URI`` statement used in a recipe (e.g. +than any multi-repository :term:`SRC_URI` statement used in a recipe (e.g. see the previous section). You can keep kernel Metadata in a "kernel-cache", which is a directory containing configuration fragments. As with any Metadata kept outside -the recipe-space, you simply need to use the ``SRC_URI`` statement with +the recipe-space, you simply need to use the :term:`SRC_URI` statement with the "type=kmeta" attribute. Doing so makes the kernel Metadata available during the configuration phase. -If you modify the Metadata, you must not forget to update the ``SRCREV`` +If you modify the Metadata, you must not forget to update the :term:`SRCREV` statements in the kernel's recipe. In particular, you need to update the ``SRCREV_meta`` variable to match the commit in the ``KMETA`` branch you wish to use. Changing the data in these branches and not updating the -``SRCREV`` statements to match will cause the build to fetch an older +:term:`SRCREV` statements to match will cause the build to fetch an older commit. Organizing Your Source ====================== Many recipes based on the ``linux-yocto-custom.bb`` recipe use Linux -kernel sources that have only a single branch - "master". This type of +kernel sources that have only a single branch. This type of repository structure is fine for linear development supporting a single machine and architecture. However, if you work with multiple boards and architectures, a kernel source repository with multiple branches is more @@ -827,11 +765,11 @@ board to boot. Sometimes, these patches are works-in-progress or fundamentally wrong, yet they are still necessary for specific boards. In these situations, you most likely do not want to include these patches in every kernel you build (i.e. have the patches as part of the -lone "master" branch). It is situations like these that give rise to +default branch). It is situations like these that give rise to multiple branches used within a Linux kernel sources Git repository. -Repository organization strategies exist that maximize source reuse, -remove redundancy, and logically order your changes. This section +Here are repository organization strategies maximizing source reuse, +removing redundancy, and logically ordering your changes. This section presents strategies for the following cases: - Encapsulating patches in a feature description and only including the @@ -849,17 +787,17 @@ best for your development model. Encapsulating Patches --------------------- -if you are reusing patches from an external tree and are not working on +If you are reusing patches from an external tree and are not working on the patches, you might find the encapsulated feature to be appropriate. Given this scenario, you do not need to create any branches in the source repository. Rather, you just take the static patches you need and encapsulate them within a feature description. Once you have the feature description, you simply include that into the BSP description as -described in the "`BSP Descriptions <#bsp-descriptions>`__" section. +described in the ":ref:`kernel-dev/advanced:bsp descriptions`" section. You can find information on how to create patches and BSP descriptions -in the "`Patches <#patches>`__" and "`BSP -Descriptions <#bsp-descriptions>`__" sections. +in the ":ref:`kernel-dev/advanced:patches`" and +":ref:`kernel-dev/advanced:bsp descriptions`" sections. Machine Branches ---------------- @@ -867,20 +805,19 @@ Machine Branches When you have multiple machines and architectures to support, or you are actively working on board support, it is more efficient to create branches in the repository based on individual machines. Having machine -branches allows common source to remain in the "master" branch with any +branches allows common source to remain in the development branch with any features specific to a machine stored in the appropriate machine branch. This organization method frees you from continually reintegrating your patches into a feature. Once you have a new branch, you can set up your kernel Metadata to use the branch a couple different ways. In the recipe, you can specify the -new branch as the ``KBRANCH`` to use for the board as follows: -:: +new branch as the :term:`KBRANCH` to use for the board as follows:: KBRANCH = "mynewbranch" Another method is to use the ``branch`` command in the BSP -description: +description:: mybsp.scc: define KMACHINE mybsp @@ -894,15 +831,13 @@ description: If you find yourself with numerous branches, you might consider using a hierarchical branching system similar to what the Yocto Linux Kernel Git -repositories use: -:: +repositories use:: common/kernel_type/machine If you had two kernel types, "standard" and "small" for instance, three machines, and common as ``mydir``, the branches in your Git repository -might look like this: -: +might look like this:: mydir/base mydir/standard/base @@ -922,11 +857,8 @@ appropriate for the other branches. The "base" branches are an artifact of the way Git manages its data internally on the filesystem: Git will not allow you to use - mydir/standard - and - mydir/standard/machine_a - because it would have to create a file and a directory named - "standard". + ``mydir/standard`` and ``mydir/standard/machine_a`` because it would have to + create a file and a directory named "standard". Feature Branches ---------------- @@ -937,8 +869,7 @@ that have to be regularly updated. The Yocto Project Linux kernel tools provide for this with the ``git merge`` command. To merge a feature branch into a BSP, insert the ``git merge`` command -after any ``branch`` commands: -:: +after any ``branch`` commands:: mybsp.scc: define KMACHINE mybsp @@ -951,8 +882,6 @@ after any ``branch`` commands: include mybsp-hw.scc -.. _scc-reference: - SCC Description File Reference ============================== diff --git a/documentation/kernel-dev/kernel-dev-common.rst b/documentation/kernel-dev/common.rst index d4b60a9dc9..fda41694dc 100644 --- a/documentation/kernel-dev/kernel-dev-common.rst +++ b/documentation/kernel-dev/common.rst @@ -1,4 +1,4 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ************ Common Tasks @@ -21,11 +21,11 @@ Preparing the Build Host to Work on the Kernel Before you can do any kernel development, you need to be sure your build host is set up to use the Yocto Project. For information on how to get -set up, see the ":doc:`../dev-manual/dev-manual-start`" section in +set up, see the ":doc:`/dev-manual/start`" section in the Yocto Project Development Tasks Manual. Part of preparing the system is creating a local Git repository of the :term:`Source Directory` (``poky``) on your system. Follow the steps in the -":ref:`dev-manual/dev-manual-start:cloning the \`\`poky\`\` repository`" +":ref:`dev-manual/start:cloning the \`\`poky\`\` repository`" section in the Yocto Project Development Tasks Manual to set up your Source Directory. @@ -33,15 +33,13 @@ Source Directory. Be sure you check out the appropriate development branch or you create your local branch by checking out a specific tag to get the - desired version of Yocto Project. See the " - Checking Out by Branch in Poky - " and " - Checking Out by Tag in Poky - " sections in the Yocto Project Development Tasks Manual for more - information. + desired version of Yocto Project. See the + ":ref:`dev-manual/start:checking out by branch in poky`" and + ":ref:`dev-manual/start:checking out by tag in poky`" + sections in the Yocto Project Development Tasks Manual for more information. Kernel development is best accomplished using -:ref:`devtool <sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow>` +:ref:`devtool <sdk-manual/extensible:using \`\`devtool\`\` in your sdk workflow>` and not through traditional kernel workflow methods. The remainder of this section provides information for both scenarios. @@ -50,55 +48,46 @@ Getting Ready to Develop Using ``devtool`` Follow these steps to prepare to update the kernel image using ``devtool``. Completing this procedure leaves you with a clean kernel -image and ready to make modifications as described in the " -:ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" +image and ready to make modifications as described in the +":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" section: -1. *Initialize the BitBake Environment:* Before building an extensible - SDK, you need to initialize the BitBake build environment by sourcing - the build environment script (i.e. :ref:`structure-core-script`): - :: +#. *Initialize the BitBake Environment:* + you need to initialize the BitBake build environment by sourcing + the build environment script (i.e. :ref:`structure-core-script`):: - $ cd ~/poky + $ cd poky $ source oe-init-build-env .. note:: The previous commands assume the - Source Repositories - (i.e. - poky - ) have been cloned using Git and the local repository is named + :ref:`overview-manual/development-environment:yocto project source repositories` + (i.e. ``poky``) have been cloned using Git and the local repository is named "poky". -2. *Prepare Your local.conf File:* By default, the - :term:`MACHINE` variable is set to - "qemux86-64", which is fine if you are building for the QEMU emulator - in 64-bit mode. However, if you are not, you need to set the - ``MACHINE`` variable appropriately in your ``conf/local.conf`` file - found in the - :term:`Build Directory` (i.e. - ``~/poky/build`` in this example). +#. *Prepare Your local.conf File:* By default, the :term:`MACHINE` variable + is set to "qemux86-64", which is fine if you are building for the QEMU + emulator in 64-bit mode. However, if you are not, you need to set the + :term:`MACHINE` variable appropriately in your ``conf/local.conf`` file + found in the :term:`Build Directory` (i.e. ``poky/build`` in this example). Also, since you are preparing to work on the kernel image, you need - to set the - :term:`MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS` - variable to include kernel modules. + to set the :term:`MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS` variable to include + kernel modules. In this example we wish to build for qemux86 so we must set the - ``MACHINE`` variable to "qemux86" and also add the "kernel-modules". - As described we do this by appending to ``conf/local.conf``: - :: + :term:`MACHINE` variable to "qemux86" and also add the "kernel-modules". + As described we do this by appending to ``conf/local.conf``:: MACHINE = "qemux86" MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-modules" -3. *Create a Layer for Patches:* You need to create a layer to hold +#. *Create a Layer for Patches:* You need to create a layer to hold patches created for the kernel image. You can use the - ``bitbake-layers create-layer`` command as follows: - :: + ``bitbake-layers create-layer`` command as follows:: - $ cd ~/poky/build + $ cd poky/build $ bitbake-layers create-layer ../../meta-mylayer NOTE: Starting bitbake server... Add your new layer with 'bitbake-layers add-layer ../../meta-mylayer' @@ -107,93 +96,30 @@ section: .. note:: For background information on working with common and BSP layers, - see the " - Understanding and Creating Layers - " section in the Yocto Project Development Tasks Manual and the " - BSP Layers - " section in the Yocto Project Board Support (BSP) Developer's - Guide, respectively. For information on how to use the - bitbake-layers create-layer - command to quickly set up a layer, see the " - Creating a General Layer Using the - bitbake-layers - Script - " section in the Yocto Project Development Tasks Manual. - -4. *Inform the BitBake Build Environment About Your Layer:* As directed + see the + ":ref:`dev-manual/layers:understanding and creating layers`" + section in the Yocto Project Development Tasks Manual and the + ":ref:`bsp-guide/bsp:bsp layers`" section in the Yocto Project Board + Support (BSP) Developer's Guide, respectively. For information on how to + use the ``bitbake-layers create-layer`` command to quickly set up a layer, + see the + ":ref:`dev-manual/layers:creating a general layer using the \`\`bitbake-layers\`\` script`" + section in the Yocto Project Development Tasks Manual. + +#. *Inform the BitBake Build Environment About Your Layer:* As directed when you created your layer, you need to add the layer to the :term:`BBLAYERS` variable in the - ``bblayers.conf`` file as follows: - :: + ``bblayers.conf`` file as follows:: - $ cd ~/poky/build + $ cd poky/build $ bitbake-layers add-layer ../../meta-mylayer NOTE: Starting bitbake server... $ -5. *Build the Extensible SDK:* Use BitBake to build the extensible SDK - specifically for use with images to be run using QEMU: - :: - - $ cd ~/poky/build - $ bitbake core-image-minimal -c populate_sdk_ext - - Once - the build finishes, you can find the SDK installer file (i.e. - ``*.sh`` file) in the following directory: - ~/poky/build/tmp/deploy/sdk For this example, the installer file is - named - ``poky-glibc-x86_64-core-image-minimal-i586-toolchain-ext-DISTRO.sh`` - -6. *Install the Extensible SDK:* Use the following command to install - the SDK. For this example, install the SDK in the default - ``~/poky_sdk`` directory: - :: - - $ cd ~/poky/build/tmp/deploy/sdk - $ ./poky-glibc-x86_64-core-image-minimal-i586-toolchain-ext-3.1.2.sh - Poky (Yocto Project Reference Distro) Extensible SDK installer version 3.1.2 - ============================================================================ - Enter target directory for SDK (default: ~/poky_sdk): - You are about to install the SDK to "/home/scottrif/poky_sdk". Proceed [Y/n]? Y - Extracting SDK......................................done - Setting it up... - Extracting buildtools... - Preparing build system... - Parsing recipes: 100% |#################################################################| Time: 0:00:52 - Initializing tasks: 100% |############## ###############################################| Time: 0:00:04 - Checking sstate mirror object availability: 100% |######################################| Time: 0:00:00 - Parsing recipes: 100% |#################################################################| Time: 0:00:33 - Initializing tasks: 100% |##############################################################| Time: 0:00:00 - done - SDK has been successfully set up and is ready to be used. - Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g. - $ . /home/scottrif/poky_sdk/environment-setup-i586-poky-linux - - -7. *Set Up a New Terminal to Work With the Extensible SDK:* You must set - up a new terminal to work with the SDK. You cannot use the same - BitBake shell used to build the installer. - - After opening a new shell, run the SDK environment setup script as - directed by the output from installing the SDK: - :: - - $ source ~/poky_sdk/environment-setup-i586-poky-linux - "SDK environment now set up; additionally you may now run devtool to perform development tasks. - Run devtool --help for further details. - - .. note:: - - If you get a warning about attempting to use the extensible SDK in - an environment set up to run BitBake, you did not use a new shell. - -8. *Build the Clean Image:* The final step in preparing to work on the - kernel is to build an initial image using ``devtool`` in the new - terminal you just set up and initialized for SDK work: - :: +#. *Build the Clean Image:* The final step in preparing to work on the + kernel is to build an initial image using ``bitbake``:: - $ devtool build-image + $ bitbake core-image-minimal Parsing recipes: 100% |##########################################| Time: 0:00:05 Parsing of 830 .bb files complete (0 cached, 830 parsed). 1299 targets, 47 skipped, 0 masked, 0 errors. WARNING: No packages to add, building image core-image-minimal unmodified @@ -205,18 +131,17 @@ section: NOTE: Executing SetScene Tasks NOTE: Executing RunQueue Tasks NOTE: Tasks Summary: Attempted 2866 tasks of which 2604 didn't need to be rerun and all succeeded. - NOTE: Successfully built core-image-minimal. You can find output files in /home/scottrif/poky_sdk/tmp/deploy/images/qemux86 If you were building for actual hardware and not for emulation, you could flash the image to a USB stick on ``/dev/sdd`` and boot your device. For an example that uses a Minnowboard, see the - `TipsAndTricks/KernelDevelopmentWithEsdk <https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk>`__ + :yocto_wiki:`TipsAndTricks/KernelDevelopmentWithEsdk </TipsAndTricks/KernelDevelopmentWithEsdk>` Wiki page. At this point you have set up to start making modifications to the -kernel by using the extensible SDK. For a continued example, see the -":ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" +kernel. For a continued example, see the +":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" section. Getting Ready for Traditional Kernel Development @@ -230,43 +155,37 @@ you will be editing these files. Follow these steps to prepare to update the kernel image using traditional kernel development flow with the Yocto Project. Completing this procedure leaves you ready to make modifications to the kernel -source as described in the ":ref:`kernel-dev/kernel-dev-common:using traditional kernel development to patch the kernel`" +source as described in the ":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" section: -1. *Initialize the BitBake Environment:* Before you can do anything +#. *Initialize the BitBake Environment:* Before you can do anything using BitBake, you need to initialize the BitBake build environment by sourcing the build environment script (i.e. :ref:`structure-core-script`). Also, for this example, be sure that the local branch you have checked out for ``poky`` is the Yocto Project &DISTRO_NAME; branch. If you need to checkout out the &DISTRO_NAME; branch, see the - ":ref:`dev-manual/dev-manual-start:checking out by branch in poky`" - section in the Yocto Project Development Tasks Manual. - :: + ":ref:`dev-manual/start:checking out by branch in poky`" + section in the Yocto Project Development Tasks Manual:: - $ cd ~/poky + $ cd poky $ git branch master - * &DISTRO_NAME; + * &DISTRO_NAME_NO_CAP; $ source oe-init-build-env .. note:: The previous commands assume the - Source Repositories - (i.e. - poky - ) have been cloned using Git and the local repository is named + :ref:`overview-manual/development-environment:yocto project source repositories` + (i.e. ``poky``) have been cloned using Git and the local repository is named "poky". -2. *Prepare Your local.conf File:* By default, the - :term:`MACHINE` variable is set to - "qemux86-64", which is fine if you are building for the QEMU emulator - in 64-bit mode. However, if you are not, you need to set the - ``MACHINE`` variable appropriately in your ``conf/local.conf`` file - found in the - :term:`Build Directory` (i.e. - ``~/poky/build`` in this example). +#. *Prepare Your local.conf File:* By default, the :term:`MACHINE` variable is + set to "qemux86-64", which is fine if you are building for the QEMU emulator + in 64-bit mode. However, if you are not, you need to set the :term:`MACHINE` + variable appropriately in your ``conf/local.conf`` file found in the + :term:`Build Directory` (i.e. ``poky/build`` in this example). Also, since you are preparing to work on the kernel image, you need to set the @@ -274,19 +193,17 @@ section: variable to include kernel modules. In this example we wish to build for qemux86 so we must set the - ``MACHINE`` variable to "qemux86" and also add the "kernel-modules". - As described we do this by appending to ``conf/local.conf``: - :: + :term:`MACHINE` variable to "qemux86" and also add the "kernel-modules". + As described we do this by appending to ``conf/local.conf``:: MACHINE = "qemux86" MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-modules" -3. *Create a Layer for Patches:* You need to create a layer to hold +#. *Create a Layer for Patches:* You need to create a layer to hold patches created for the kernel image. You can use the - ``bitbake-layers create-layer`` command as follows: - :: + ``bitbake-layers create-layer`` command as follows:: - $ cd ~/poky/build + $ cd poky/build $ bitbake-layers create-layer ../../meta-mylayer NOTE: Starting bitbake server... Add your new layer with 'bitbake-layers add-layer ../../meta-mylayer' @@ -294,31 +211,27 @@ section: .. note:: For background information on working with common and BSP layers, - see the " - Understanding and Creating Layers - " section in the Yocto Project Development Tasks Manual and the " - BSP Layers - " section in the Yocto Project Board Support (BSP) Developer's - Guide, respectively. For information on how to use the - bitbake-layers create-layer - command to quickly set up a layer, see the " - Creating a General Layer Using the - bitbake-layers - Script - " section in the Yocto Project Development Tasks Manual. - -4. *Inform the BitBake Build Environment About Your Layer:* As directed + see the + ":ref:`dev-manual/layers:understanding and creating layers`" + section in the Yocto Project Development Tasks Manual and the + ":ref:`bsp-guide/bsp:bsp layers`" section in the Yocto Project Board + Support (BSP) Developer's Guide, respectively. For information on how to + use the ``bitbake-layers create-layer`` command to quickly set up a layer, + see the + ":ref:`dev-manual/layers:creating a general layer using the \`\`bitbake-layers\`\` script`" + section in the Yocto Project Development Tasks Manual. + +#. *Inform the BitBake Build Environment About Your Layer:* As directed when you created your layer, you need to add the layer to the :term:`BBLAYERS` variable in the - ``bblayers.conf`` file as follows: - :: + ``bblayers.conf`` file as follows:: - $ cd ~/poky/build + $ cd poky/build $ bitbake-layers add-layer ../../meta-mylayer NOTE: Starting bitbake server ... $ -5. *Create a Local Copy of the Kernel Git Repository:* You can find Git +#. *Create a Local Copy of the Kernel Git Repository:* You can find Git repositories of supported Yocto Project kernels organized under "Yocto Linux Kernel" in the Yocto Project Source Repositories at :yocto_git:`/`. @@ -330,18 +243,7 @@ section: ``standard/base`` branch. The following commands show how to create a local copy of the - ``linux-yocto-4.12`` kernel and be in the ``standard/base`` branch. - - .. note:: - - The - linux-yocto-4.12 - kernel can be used with the Yocto Project 2.4 release and forward. - You cannot use the - linux-yocto-4.12 - kernel with releases prior to Yocto Project 2.4: - - :: + ``linux-yocto-4.12`` kernel and be in the ``standard/base`` branch:: $ cd ~ $ git clone git://git.yoctoproject.org/linux-yocto-4.12 --branch standard/base @@ -351,9 +253,16 @@ section: remote: Total 6097195 (delta 5152604), reused 6096847 (delta 5152256) Receiving objects: 100% (6097195/6097195), 1.24 GiB | 7.81 MiB/s, done. Resolving deltas: 100% (5152604/5152604), done. Checking connectivity... done. - Checking out files: 100% (59846/59846), done. + Checking out files: 100% (59846/59846), done. -6. *Create a Local Copy of the Kernel Cache Git Repository:* For + .. note:: + + The ``linux-yocto-4.12`` kernel can be used with the Yocto Project 2.4 + release and forward. + You cannot use the ``linux-yocto-4.12`` kernel with releases prior to + Yocto Project 2.4. + +#. *Create a Local Copy of the Kernel Cache Git Repository:* For simplicity, it is recommended that you create your copy of the kernel cache Git repository outside of the :term:`Source Directory`, which is @@ -361,8 +270,7 @@ section: the ``yocto-4.12`` branch. The following commands show how to create a local copy of the - ``yocto-kernel-cache`` and be in the ``yocto-4.12`` branch: - :: + ``yocto-kernel-cache`` and switch to the ``yocto-4.12`` branch:: $ cd ~ $ git clone git://git.yoctoproject.org/yocto-kernel-cache --branch yocto-4.12 @@ -376,8 +284,7 @@ section: At this point, you are ready to start making modifications to the kernel using traditional kernel development steps. For a continued example, see -the "`Using Traditional Kernel Development to Patch the -Kernel <#using-traditional-kernel-development-to-patch-the-kernel>`__" +the ":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" section. Creating and Preparing a Layer @@ -389,19 +296,16 @@ layer contains its own :term:`BitBake` append files (``.bbappend``) and provides a convenient mechanism to create your own recipe files (``.bb``) as well as store and use kernel patch files. For background information on working with layers, see the -":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`" +":ref:`dev-manual/layers:understanding and creating layers`" section in the Yocto Project Development Tasks Manual. .. note:: The Yocto Project comes with many tools that simplify tasks you need - to perform. One such tool is the - bitbake-layers create-layer - command, which simplifies creating a new layer. See the " - Creating a General Layer Using the - bitbake-layers - Script - " section in the Yocto Project Development Tasks Manual for + to perform. One such tool is the ``bitbake-layers create-layer`` + command, which simplifies creating a new layer. See the + ":ref:`dev-manual/layers:creating a general layer using the \`\`bitbake-layers\`\` script`" + section in the Yocto Project Development Tasks Manual for information on how to use this script to quick set up a new layer. To better understand the layer you create for kernel development, the @@ -409,24 +313,17 @@ following section describes how to create a layer without the aid of tools. These steps assume creation of a layer named ``mylayer`` in your home directory: -1. *Create Structure*: Create the layer's structure: - :: +#. *Create Structure*: Create the layer's structure:: - $ cd $HOME - $ mkdir meta-mylayer - $ mkdir meta-mylayer/conf - $ mkdir meta-mylayer/recipes-kernel - $ mkdir meta-mylayer/recipes-kernel/linux - $ mkdir meta-mylayer/recipes-kernel/linux/linux-yocto + $ mkdir -p meta-mylayer/conf meta-mylayer/recipes-kernel/linux/linux-yocto The ``conf`` directory holds your configuration files, while the ``recipes-kernel`` directory holds your append file and eventual patch files. -2. *Create the Layer Configuration File*: Move to the +#. *Create the Layer Configuration File*: Move to the ``meta-mylayer/conf`` directory and create the ``layer.conf`` file as - follows: - :: + follows:: # We have a conf and classes directory, add to BBPATH BBPATH .= ":${LAYERDIR}" @@ -441,23 +338,22 @@ home directory: Notice ``mylayer`` as part of the last three statements. -3. *Create the Kernel Recipe Append File*: Move to the +#. *Create the Kernel Recipe Append File*: Move to the ``meta-mylayer/recipes-kernel/linux`` directory and create the kernel's append file. This example uses the ``linux-yocto-4.12`` kernel. Thus, the name of the append file is - ``linux-yocto_4.12.bbappend``: - :: + ``linux-yocto_4.12.bbappend``:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" - SRC_URI_append = " file://patch-file-one" - SRC_URI_append = " file://patch-file-two" - SRC_URI_append = " file://patch-file-three" + SRC_URI += "file://patch-file-one.patch" + SRC_URI += "file://patch-file-two.patch" + SRC_URI += "file://patch-file-three.patch" The :term:`FILESEXTRAPATHS` and :term:`SRC_URI` statements enable the OpenEmbedded build system to find patch files. For more information on using append files, see the - ":ref:`dev-manual/dev-manual-common-tasks:using .bbappend files in your layer`" + ":ref:`dev-manual/layers:appending other layers metadata with your layer`" section in the Yocto Project Development Tasks Manual. Modifying an Existing Recipe @@ -471,15 +367,15 @@ the :term:`Source Directory` in Modifying an existing recipe can consist of the following: -- Creating the append file +- :ref:`kernel-dev/common:creating the append file` -- Applying patches +- :ref:`kernel-dev/common:applying patches` -- Changing the configuration +- :ref:`kernel-dev/common:changing the configuration` Before modifying an existing recipe, be sure that you have created a -minimal, custom layer from which you can work. See the "`Creating and -Preparing a Layer <#creating-and-preparing-a-layer>`__" section for +minimal, custom layer from which you can work. See the +":ref:`kernel-dev/common:creating and preparing a layer`" section for information. Creating the Append File @@ -487,72 +383,65 @@ Creating the Append File You create this file in your custom layer. You also name it accordingly based on the linux-yocto recipe you are using. For example, if you are -modifying the ``meta/recipes-kernel/linux/linux-yocto_4.12.bb`` recipe, +modifying the ``meta/recipes-kernel/linux/linux-yocto_6.1.bb`` recipe, the append file will typically be located as follows within your custom layer: -:: - your-layer/recipes-kernel/linux/linux-yocto_4.12.bbappend +.. code-block:: none + + your-layer/recipes-kernel/linux/linux-yocto_6.1.bbappend The append file should initially extend the :term:`FILESPATH` search path by prepending the directory that contains your files to the :term:`FILESEXTRAPATHS` -variable as follows: -:: +variable as follows:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" The path ``${``\ :term:`THISDIR`\ ``}/${``\ :term:`PN`\ ``}`` expands to "linux-yocto" in the current directory for this example. If you add any new files that modify the kernel recipe and you have -extended ``FILESPATH`` as described above, you must place the files in -your layer in the following area: -:: +extended :term:`FILESPATH` as described above, you must place the files in +your layer in the following area:: your-layer/recipes-kernel/linux/linux-yocto/ .. note:: If you are working on a new machine Board Support Package (BSP), be - sure to refer to the - Yocto Project Board Support Package (BSP) Developer's Guide - . + sure to refer to the :doc:`/bsp-guide/index`. As an example, consider the following append file used by the BSPs in ``meta-yocto-bsp``: -:: - meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.12.bbappend +.. code-block:: none -The following listing shows the file. Be aware that the actual commit ID -strings in this example listing might be different than the actual -strings in the file from the ``meta-yocto-bsp`` layer upstream. -:: + meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.1.bbappend - KBRANCH_genericx86 = "standard/base" - KBRANCH_genericx86-64 = "standard/base" +Here are the contents of this file. Be aware that the actual commit ID +strings in this example listing might be different than the actual +strings in the file from the ``meta-yocto-bsp`` layer upstream:: - KMACHINE_genericx86 ?= "common-pc" - KMACHINE_genericx86-64 ?= "common-pc-64" - KBRANCH_edgerouter = "standard/edgerouter" - KBRANCH_beaglebone = "standard/beaglebone" + KBRANCH:genericx86 = "v6.1/standard/base" + KBRANCH:genericx86-64 = "v6.1/standard/base" + KBRANCH:beaglebone-yocto = "v6.1/standard/beaglebone" - SRCREV_machine_genericx86 ?= "d09f2ce584d60ecb7890550c22a80c48b83c2e19" - SRCREV_machine_genericx86-64 ?= "d09f2ce584d60ecb7890550c22a80c48b83c2e19" - SRCREV_machine_edgerouter ?= "b5c8cfda2dfe296410d51e131289fb09c69e1e7d" - SRCREV_machine_beaglebone ?= "b5c8cfda2dfe296410d51e131289fb09c69e1e7d" + KMACHINE:genericx86 ?= "common-pc" + KMACHINE:genericx86-64 ?= "common-pc-64" + KMACHINE:beaglebone-yocto ?= "beaglebone" + SRCREV_machine:genericx86 ?= "6ec439b4b456ce929c4c07fe457b5d6a4b468e86" + SRCREV_machine:genericx86-64 ?= "6ec439b4b456ce929c4c07fe457b5d6a4b468e86" + SRCREV_machine:beaglebone-yocto ?= "423e1996694b61fbfc8ec3bf062fc6461d64fde1" - COMPATIBLE_MACHINE_genericx86 = "genericx86" - COMPATIBLE_MACHINE_genericx86-64 = "genericx86-64" - COMPATIBLE_MACHINE_edgerouter = "edgerouter" - COMPATIBLE_MACHINE_beaglebone = "beaglebone" + COMPATIBLE_MACHINE:genericx86 = "genericx86" + COMPATIBLE_MACHINE:genericx86-64 = "genericx86-64" + COMPATIBLE_MACHINE:beaglebone-yocto = "beaglebone-yocto" - LINUX_VERSION_genericx86 = "4.12.7" - LINUX_VERSION_genericx86-64 = "4.12.7" - LINUX_VERSION_edgerouter = "4.12.10" - LINUX_VERSION_beaglebone = "4.12.10" + LINUX_VERSION:genericx86 = "6.1.30" + LINUX_VERSION:genericx86-64 = "6.1.30" + LINUX_VERSION:beaglebone-yocto = "6.1.20" This append file contains statements used to support several BSPs that ship with the @@ -587,19 +476,17 @@ the append file. For example, suppose you had some configuration options in a file called ``network_configs.cfg``. You can place that file inside a directory -named ``linux-yocto`` and then add a ``SRC_URI`` statement such as the +named ``linux-yocto`` and then add a :term:`SRC_URI` statement such as the following to the append file. When the OpenEmbedded build system builds -the kernel, the configuration options are picked up and applied. -:: +the kernel, the configuration options are picked up and applied:: SRC_URI += "file://network_configs.cfg" To group related configurations into multiple files, you perform a similar procedure. Here is an example that groups separate configurations specifically for Ethernet and graphics into their own -files and adds the configurations by using a ``SRC_URI`` statement like -the following in your append file: -:: +files and adds the configurations by using a :term:`SRC_URI` statement like +the following in your append file:: SRC_URI += "file://myconfig.cfg \ file://eth.cfg \ @@ -613,7 +500,7 @@ recipe is processed. .. note:: - Other methods exist to accomplish grouping and defining configuration + There are other ways of grouping and defining configuration options. For example, if you are working with a local clone of the kernel repository, you could checkout the kernel's ``meta`` branch, make your changes, and then push the changes to the local bare clone @@ -623,9 +510,9 @@ recipe is processed. added to the Yocto Project. In general, however, the Yocto Project maintainers take care of - moving the ``SRC_URI``-specified configuration options to the - kernel's ``meta`` branch. Not only is it easier for BSP developers to - not have to worry about putting those configurations in the branch, + moving the :term:`SRC_URI`-specified configuration options to the + kernel's ``meta`` branch. Not only is it easier for BSP developers + not to have to put those configurations in the branch, but having the maintainers do it allows them to apply 'global' knowledge about the kinds of common configuration options multiple BSPs in the tree are typically using. This allows for promotion of @@ -643,8 +530,7 @@ reference them in :term:`SRC_URI` statements. For example, you can apply a three-patch series by adding the following -lines to your linux-yocto ``.bbappend`` file in your layer: -:: +lines to your linux-yocto ``.bbappend`` file in your layer:: SRC_URI += "file://0001-first-change.patch" SRC_URI += "file://0002-second-change.patch" @@ -656,9 +542,9 @@ and applies the patches before building the kernel. For a detailed example showing how to patch the kernel using ``devtool``, see the -":ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" +":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" and -":ref:`kernel-dev/kernel-dev-common:using traditional kernel development to patch the kernel`" +":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" sections. Changing the Configuration @@ -674,39 +560,42 @@ If you have a complete, working Linux kernel ``.config`` file you want to use for the configuration, as before, copy that file to the appropriate ``${PN}`` directory in your layer's ``recipes-kernel/linux`` directory, and rename the copied file to "defconfig". Then, add the -following lines to the linux-yocto ``.bbappend`` file in your layer: -:: +following lines to the linux-yocto ``.bbappend`` file in your layer:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" SRC_URI += "file://defconfig" -The ``SRC_URI`` tells the build system how to search +The :term:`SRC_URI` tells the build system how to search for the file, while the :term:`FILESEXTRAPATHS` extends the :term:`FILESPATH` variable (search directories) to include the ``${PN}`` directory you created to hold the configuration changes. +You can also use a regular ``defconfig`` file, as generated by the +:ref:`ref-tasks-savedefconfig` +task instead of a complete ``.config`` file. This only specifies the +non-default configuration values. You need to additionally set +:term:`KCONFIG_MODE` +in the linux-yocto ``.bbappend`` file in your layer:: + + KCONFIG_MODE = "alldefconfig" + .. note:: - The build system applies the configurations from the - defconfig + The build system applies the configurations from the ``defconfig`` file before applying any subsequent configuration fragments. The final kernel configuration is a combination of the configurations in - the - defconfig - file and any configuration fragments you provide. You need to realize - that if you have any configuration fragments, the build system - applies these on top of and after applying the existing - defconfig - file configurations. + the ``defconfig`` file and any configuration fragments you provide. You need + to realize that if you have any configuration fragments, the build system + applies these on top of and after applying the existing ``defconfig`` file + configurations. Generally speaking, the preferred approach is to determine the incremental change you want to make and add that as a configuration fragment. For example, if you want to add support for a basic serial console, create a file named ``8250.cfg`` in the ``${PN}`` directory -with the following content (without indentation): -:: +with the following content (without indentation):: CONFIG_SERIAL_8250=y CONFIG_SERIAL_8250_CONSOLE=y @@ -717,11 +606,10 @@ with the following content (without indentation): CONFIG_SERIAL_CORE_CONSOLE=y Next, include this -configuration fragment and extend the ``FILESPATH`` variable in your -``.bbappend`` file: -:: +configuration fragment and extend the :term:`FILESPATH` variable in your +``.bbappend`` file:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" SRC_URI += "file://8250.cfg" The next time you run BitBake to build the @@ -729,7 +617,7 @@ Linux kernel, BitBake detects the change in the recipe and fetches and applies the new configuration before building the kernel. For a detailed example showing how to configure the kernel, see the -"`Configuring the Kernel <#configuring-the-kernel>`__" section. +":ref:`kernel-dev/common:configuring the kernel`" section. Using an "In-Tree"  ``defconfig`` File -------------------------------------- @@ -738,8 +626,7 @@ It might be desirable to have kernel configuration fragment support through a ``defconfig`` file that is pulled from the kernel source tree for the configured machine. By default, the OpenEmbedded build system looks for ``defconfig`` files in the layer used for Metadata, which is -"out-of-tree", and then configures them using the following: -:: +"out-of-tree", and then configures them using the following:: SRC_URI += "file://defconfig" @@ -752,26 +639,24 @@ append files, you can direct the OpenEmbedded build system to use a ``defconfig`` file that is "in-tree". To specify an "in-tree" ``defconfig`` file, use the following statement -form: -:: +form:: - KBUILD_DEFCONFIG_KMACHINE ?= defconfig_file + KBUILD_DEFCONFIG:<machine> ?= "defconfig_file" -Here is an example -that assigns the ``KBUILD_DEFCONFIG`` variable based on "raspberrypi2" -and provides the path to the "in-tree" ``defconfig`` file to be used for -a Raspberry Pi 2, which is based on the Broadcom 2708/2709 chipset: -:: +Here is an example that assigns the :term:`KBUILD_DEFCONFIG` variable utilizing +an override for the "raspberrypi2" :term:`MACHINE` and provides the path to the +"in-tree" ``defconfig`` file to be used for a Raspberry Pi 2, which is based on +the Broadcom 2708/2709 chipset:: - KBUILD_DEFCONFIG_raspberrypi2 ?= "bcm2709_defconfig" + KBUILD_DEFCONFIG:raspberrypi2 ?= "bcm2709_defconfig" Aside from modifying your kernel recipe and providing your own ``defconfig`` file, you need to be sure no files or statements set -``SRC_URI`` to use a ``defconfig`` other than your "in-tree" file (e.g. -a kernel's ``linux-``\ machine\ ``.inc`` file). In other words, if the +:term:`SRC_URI` to use a ``defconfig`` other than your "in-tree" file (e.g. +a kernel's ``linux-``\ `machine`\ ``.inc`` file). In other words, if the build system detects a statement that identifies an "out-of-tree" ``defconfig`` file, that statement will override your -``KBUILD_DEFCONFIG`` variable. +:term:`KBUILD_DEFCONFIG` variable. See the :term:`KBUILD_DEFCONFIG` @@ -781,15 +666,14 @@ Using ``devtool`` to Patch the Kernel ===================================== The steps in this procedure show you how you can patch the kernel using -the extensible SDK and ``devtool``. +``devtool``. .. note:: Before attempting this procedure, be sure you have performed the - steps to get ready for updating the kernel as described in the " - Getting Ready to Develop Using - devtool - " section. + steps to get ready for updating the kernel as described in the + ":ref:`kernel-dev/common:getting ready to develop using \`\`devtool\`\``" + section. Patching the kernel involves changing or adding configurations to an existing kernel, changing or adding recipes to the kernel that are @@ -801,31 +685,27 @@ output at boot time through ``printk`` statements in the kernel's ``calibrate.c`` source code file. Applying the patch and booting the modified image causes the added messages to appear on the emulator's console. The example is a continuation of the setup procedure found in -the ":ref:`kernel-dev/kernel-dev-common:getting ready to develop using \`\`devtool\`\``" Section. +the ":ref:`kernel-dev/common:getting ready to develop using \`\`devtool\`\``" Section. -1. *Check Out the Kernel Source Files:* First you must use ``devtool`` - to checkout the kernel source code in its workspace. Be sure you are - in the terminal set up to do work with the extensible SDK. +#. *Check Out the Kernel Source Files:* First you must use ``devtool`` + to checkout the kernel source code in its workspace. .. note:: - See this - step - in the " - Getting Ready to Develop Using - devtool - " section for more information. + See this step in the + ":ref:`kernel-dev/common:getting ready to develop using \`\`devtool\`\``" + section for more information. - Use the following ``devtool`` command to check out the code: - :: + Use the following ``devtool`` command to check out the code:: $ devtool modify linux-yocto .. note:: - During the checkout operation, a bug exists that could cause - errors such as the following to appear: - :: + During the checkout operation, there is a bug that could cause + errors such as the following: + + .. code-block:: none ERROR: Taskhash mismatch 2c793438c2d9f8c3681fd5f7bc819efa versus be3a89ce7c47178880ba7bf6293d7404 for @@ -835,21 +715,19 @@ the ":ref:`kernel-dev/kernel-dev-common:getting ready to develop using \`\`devto You can safely ignore these messages. The source code is correctly checked out. -2. *Edit the Source Files* Follow these steps to make some simple +#. *Edit the Source Files* Follow these steps to make some simple changes to the source files: - 1. *Change the working directory*: In the previous step, the output + #. *Change the working directory*: In the previous step, the output noted where you can find the source files (e.g. - ``~/poky_sdk/workspace/sources/linux-yocto``). Change to where the + ``poky_sdk/workspace/sources/linux-yocto``). Change to where the kernel source code is before making your edits to the - ``calibrate.c`` file: - :: + ``calibrate.c`` file:: - $ cd ~/poky_sdk/workspace/sources/linux-yocto + $ cd poky_sdk/workspace/sources/linux-yocto - 2. *Edit the source file*: Edit the ``init/calibrate.c`` file to have - the following changes: - :: + #. *Edit the source file*: Edit the ``init/calibrate.c`` file to have + the following changes:: void calibrate_delay(void) { @@ -868,42 +746,39 @@ the ":ref:`kernel-dev/kernel-dev-common:getting ready to develop using \`\`devto . . -3. *Build the Updated Kernel Source:* To build the updated kernel - source, use ``devtool``: - :: +#. *Build the Updated Kernel Source:* To build the updated kernel + source, use ``devtool``:: $ devtool build linux-yocto -4. *Create the Image With the New Kernel:* Use the +#. *Create the Image With the New Kernel:* Use the ``devtool build-image`` command to create a new image that has the - new kernel. + new kernel:: + + $ cd ~ + $ devtool build-image core-image-minimal .. note:: If the image you originally created resulted in a Wic file, you can use an alternate method to create the new image with the updated kernel. For an example, see the steps in the - TipsAndTricks/KernelDevelopmentWithEsdk + :yocto_wiki:`TipsAndTricks/KernelDevelopmentWithEsdk </TipsAndTricks/KernelDevelopmentWithEsdk>` Wiki Page. - :: - - $ cd ~ - $ devtool build-image core-image-minimal - -5. *Test the New Image:* For this example, you can run the new image +#. *Test the New Image:* For this example, you can run the new image using QEMU to verify your changes: - 1. *Boot the image*: Boot the modified image in the QEMU emulator - using this command: - :: + #. *Boot the image*: Boot the modified image in the QEMU emulator + using this command:: $ runqemu qemux86 - 2. *Verify the changes*: Log into the machine using ``root`` with no + #. *Verify the changes*: Log into the machine using ``root`` with no password and then use the following shell command to scroll through the console's boot output. - :: + + .. code-block:: none # dmesg | less @@ -911,58 +786,54 @@ the ":ref:`kernel-dev/kernel-dev-common:getting ready to develop using \`\`devto the results of your ``printk`` statements as part of the output when you scroll down the console window. -6. *Stage and commit your changes*: Within your eSDK terminal, change +#. *Stage and commit your changes*: Change your working directory to where you modified the ``calibrate.c`` file - and use these Git commands to stage and commit your changes: - :: + and use these Git commands to stage and commit your changes:: - $ cd ~/poky_sdk/workspace/sources/linux-yocto + $ cd poky_sdk/workspace/sources/linux-yocto $ git status $ git add init/calibrate.c $ git commit -m "calibrate: Add printk example" -7. *Export the Patches and Create an Append File:* To export your +#. *Export the Patches and Create an Append File:* To export your commits as patches and create a ``.bbappend`` file, use the following - command in the terminal used to work with the extensible SDK. This - example uses the previously established layer named ``meta-mylayer``. + command. This example uses the previously established layer named ``meta-mylayer``:: - .. note:: + $ devtool finish linux-yocto ~/meta-mylayer - See Step 3 of the " - Getting Ready to Develop Using devtool - " section for information on setting up this layer. + .. note:: - $ devtool finish linux-yocto ~/meta-mylayer + See Step 3 of the + ":ref:`kernel-dev/common:getting ready to develop using \`\`devtool\`\``" + section for information on setting up this layer. Once the command finishes, the patches and the ``.bbappend`` file are located in the ``~/meta-mylayer/recipes-kernel/linux`` directory. -8. *Build the Image With Your Modified Kernel:* You can now build an +#. *Build the Image With Your Modified Kernel:* You can now build an image that includes your kernel patches. Execute the following - command from your - :term:`Build Directory` in the terminal - set up to run BitBake: - :: + command from your :term:`Build Directory` in the terminal + set up to run BitBake:: - $ cd ~/poky/build + $ cd poky/build $ bitbake core-image-minimal Using Traditional Kernel Development to Patch the Kernel ======================================================== The steps in this procedure show you how you can patch the kernel using -traditional kernel development (i.e. not using ``devtool`` and the -extensible SDK as described in the -":ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" +traditional kernel development (i.e. not using ``devtool`` +as described in the +":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" section). .. note:: Before attempting this procedure, be sure you have performed the - steps to get ready for updating the kernel as described in the " - Getting Ready for Traditional Kernel Development - " section. + steps to get ready for updating the kernel as described in the + ":ref:`kernel-dev/common:getting ready for traditional kernel development`" + section. Patching the kernel involves changing or adding configurations to an existing kernel, changing or adding recipes to the kernel that are @@ -974,28 +845,25 @@ emulator console output at boot time through ``printk`` statements in the kernel's ``calibrate.c`` source code file. Applying the patch and booting the modified image causes the added messages to appear on the emulator's console. The example is a continuation of the setup procedure -found in the "`Getting Ready for Traditional Kernel -Development <#getting-ready-for-traditional-kernel-development>`__" +found in the +":ref:`kernel-dev/common:getting ready for traditional kernel development`" Section. -1. *Edit the Source Files* Prior to this step, you should have used Git +#. *Edit the Source Files* Prior to this step, you should have used Git to create a local copy of the repository for your kernel. Assuming - you created the repository as directed in the "`Getting Ready for - Traditional Kernel - Development <#getting-ready-for-traditional-kernel-development>`__" + you created the repository as directed in the + ":ref:`kernel-dev/common:getting ready for traditional kernel development`" section, use the following commands to edit the ``calibrate.c`` file: - 1. *Change the working directory*: You need to locate the source - files in the local copy of the kernel Git repository: Change to + #. *Change the working directory*: You need to locate the source + files in the local copy of the kernel Git repository. Change to where the kernel source code is before making your edits to the - ``calibrate.c`` file: - :: + ``calibrate.c`` file:: $ cd ~/linux-yocto-4.12/init - 2. *Edit the source file*: Edit the ``calibrate.c`` file to have the - following changes: - :: + #. *Edit the source file*: Edit the ``calibrate.c`` file to have the + following changes:: void calibrate_delay(void) { @@ -1014,9 +882,8 @@ Section. . . -2. *Stage and Commit Your Changes:* Use standard Git commands to stage - and commit the changes you just made: - :: +#. *Stage and Commit Your Changes:* Use standard Git commands to stage + and commit the changes you just made:: $ git add calibrate.c $ git commit -m "calibrate.c - Added some printk statements" @@ -1025,55 +892,49 @@ Section. stage and commit your changes, the OpenEmbedded Build System will not pick up the changes. -3. *Update Your local.conf File to Point to Your Source Files:* In +#. *Update Your local.conf File to Point to Your Source Files:* In addition to your ``local.conf`` file specifying to use "kernel-modules" and the "qemux86" machine, it must also point to the updated kernel source files. Add :term:`SRC_URI` and :term:`SRCREV` statements similar - to the following to your ``local.conf``: - :: + to the following to your ``local.conf``:: - $ cd ~/poky/build/conf + $ cd poky/build/conf - Add the following to the ``local.conf``: - :: + Add the following to the ``local.conf``:: - SRC_URI_pn-linux-yocto = "git:///path-to/linux-yocto-4.12;protocol=file;name=machine;branch=standard/base; \ + SRC_URI:pn-linux-yocto = "git:///path-to/linux-yocto-4.12;protocol=file;name=machine;branch=standard/base; \ git:///path-to/yocto-kernel-cache;protocol=file;type=kmeta;name=meta;branch=yocto-4.12;destsuffix=${KMETA}" - SRCREV_meta_qemux86 = "${AUTOREV}" - SRCREV_machine_qemux86 = "${AUTOREV}" + SRCREV_meta:qemux86 = "${AUTOREV}" + SRCREV_machine:qemux86 = "${AUTOREV}" .. note:: - Be sure to replace - path-to + Be sure to replace `path-to` with the pathname to your local Git repositories. Also, you must be sure to specify the correct branch and machine types. For this - example, the branch is - standard/base - and the machine is "qemux86". + example, the branch is ``standard/base`` and the machine is ``qemux86``. -4. *Build the Image:* With the source modified, your changes staged and +#. *Build the Image:* With the source modified, your changes staged and committed, and the ``local.conf`` file pointing to the kernel files, - you can now use BitBake to build the image: - :: + you can now use BitBake to build the image:: - $ cd ~/poky/build + $ cd poky/build $ bitbake core-image-minimal -5. *Boot the image*: Boot the modified image in the QEMU emulator using +#. *Boot the image*: Boot the modified image in the QEMU emulator using this command. When prompted to login to the QEMU console, use "root" - with no password: - :: + with no password:: - $ cd ~/poky/build + $ cd poky/build $ runqemu qemux86 -6. *Look for Your Changes:* As QEMU booted, you might have seen your +#. *Look for Your Changes:* As QEMU booted, you might have seen your changes rapidly scroll by. If not, use these commands to see your changes: - :: + + .. code-block:: none # dmesg | less @@ -1081,70 +942,60 @@ Section. ``printk`` statements as part of the output when you scroll down the console window. -7. *Generate the Patch File:* Once you are sure that your patch works +#. *Generate the Patch File:* Once you are sure that your patch works correctly, you can generate a ``*.patch`` file in the kernel source - repository: - :: + repository:: $ cd ~/linux-yocto-4.12/init $ git format-patch -1 0001-calibrate.c-Added-some-printk-statements.patch -8. *Move the Patch File to Your Layer:* In order for subsequent builds +#. *Move the Patch File to Your Layer:* In order for subsequent builds to pick up patches, you need to move the patch file you created in the previous step to your layer ``meta-mylayer``. For this example, the layer created earlier is located in your home directory as ``meta-mylayer``. When the layer was created using the ``yocto-create`` script, no additional hierarchy was created to support patches. Before moving the patch file, you need to add - additional structure to your layer using the following commands: - :: + additional structure to your layer using the following commands:: $ cd ~/meta-mylayer - $ mkdir recipes-kernel - $ mkdir recipes-kernel/linux - $ mkdir recipes-kernel/linux/linux-yocto + $ mkdir -p recipes-kernel recipes-kernel/linux/linux-yocto Once you have created this hierarchy in your layer, you can move the patch file using the - following command: - :: + following command:: $ mv ~/linux-yocto-4.12/init/0001-calibrate.c-Added-some-printk-statements.patch ~/meta-mylayer/recipes-kernel/linux/linux-yocto -9. *Create the Append File:* Finally, you need to create the +#. *Create the Append File:* Finally, you need to create the ``linux-yocto_4.12.bbappend`` file and insert statements that allow the OpenEmbedded build system to find the patch. The append file needs to be in your layer's ``recipes-kernel/linux`` directory and it must be named ``linux-yocto_4.12.bbappend`` and have the following - contents: - :: + contents:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - SRC_URI_append = "file://0001-calibrate.c-Added-some-printk-statements.patch" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" + SRC_URI += "file://0001-calibrate.c-Added-some-printk-statements.patch" The :term:`FILESEXTRAPATHS` and :term:`SRC_URI` statements enable the OpenEmbedded build system to find the patch file. - For more information on append files and patches, see the "`Creating - the Append File <#creating-the-append-file>`__" and "`Applying - Patches <#applying-patches>`__" sections. You can also see the - ":ref:`dev-manual/dev-manual-common-tasks:using .bbappend files in your layer`" + For more information on append files and patches, see the + ":ref:`kernel-dev/common:creating the append file`" and + ":ref:`kernel-dev/common:applying patches`" sections. You can also see the + ":ref:`dev-manual/layers:appending other layers metadata with your layer`" section in the Yocto Project Development Tasks Manual. .. note:: - To build - core-image-minimal - again and see the effects of your patch, you can essentially - eliminate the temporary source files saved in - poky/build/tmp/work/... - and residual effects of the build by entering the following - sequence of commands: - :: - - $ cd ~/poky/build - $ bitbake -c cleanall yocto-linux + To build ``core-image-minimal`` again and see the effects of your patch, + you can essentially eliminate the temporary source files saved in + ``poky/build/tmp/work/...`` and residual effects of the build by entering + the following sequence of commands:: + + $ cd poky/build + $ bitbake -c cleanall linux-yocto $ bitbake core-image-minimal -c cleanall $ bitbake core-image-minimal $ runqemu qemux86 @@ -1165,8 +1016,8 @@ configuration fragments, and how to interactively modify your ``.config`` file to create the leanest kernel configuration file possible. -For more information on kernel configuration, see the "`Changing the -Configuration <#changing-the-configuration>`__" section. +For more information on kernel configuration, see the +":ref:`kernel-dev/common:changing the configuration`" section. Using  ``menuconfig`` --------------------- @@ -1174,21 +1025,19 @@ Using  ``menuconfig`` The easiest way to define kernel configurations is to set them through the ``menuconfig`` tool. This tool provides an interactive method with which to set kernel configurations. For general information on -``menuconfig``, see http://en.wikipedia.org/wiki/Menuconfig. +``menuconfig``, see :wikipedia:`Menuconfig`. To use the ``menuconfig`` tool in the Yocto Project development environment, you must do the following: - Because you launch ``menuconfig`` using BitBake, you must be sure to - set up your environment by running the - :ref:`structure-core-script` script found in - the :term:`Build Directory`. + set up your environment by running the :ref:`structure-core-script` script + found in the :term:`Build Directory`. - You must be sure of the state of your build's configuration in the :term:`Source Directory`. -- Your build host must have the following two packages installed: - :: +- Your build host must have the following two packages installed:: libncurses5-dev libtinfo-dev @@ -1196,8 +1045,7 @@ environment, you must do the following: The following commands initialize the BitBake environment, run the :ref:`ref-tasks-kernel_configme` task, and launch ``menuconfig``. These commands assume the Source -Directory's top-level folder is ``~/poky``: -:: +Directory's top-level folder is ``poky``:: $ cd poky $ source oe-init-build-env @@ -1212,35 +1060,20 @@ the tool and save your changes to create an updated version of the .. note:: - You can use the entire - .config - file as the - defconfig - file. For information on - defconfig - files, see the " - Changing the Configuration - ", " - Using an In-Tree - defconfig - File - , and " - Creating a - defconfig - File - " sections. + You can use the entire ``.config`` file as the ``defconfig`` file. For + information on ``defconfig`` files, see the + ":ref:`kernel-dev/common:changing the configuration`", + ":ref:`kernel-dev/common:using an "in-tree" \`\`defconfig\`\` file`", + and ":ref:`kernel-dev/common:creating a \`\`defconfig\`\` file`" + sections. Consider an example that configures the "CONFIG_SMP" setting for the ``linux-yocto-4.12`` kernel. .. note:: - The OpenEmbedded build system recognizes this kernel as - linux-yocto - through Metadata (e.g. - PREFERRED_VERSION - \_linux-yocto ?= "12.4%" - ). + The OpenEmbedded build system recognizes this kernel as ``linux-yocto`` + through Metadata (e.g. :term:`PREFERRED_VERSION`\ ``_linux-yocto ?= "4.12%"``). Once ``menuconfig`` launches, use the interface to navigate through the selections to find the configuration settings in which you are @@ -1251,15 +1084,16 @@ can find the option under "Processor Type and Features". To deselect Multi-Processing Support" and enter "N" to clear the asterisk. When you are finished, exit out and save the change. -Saving the selections updates the ``.config`` configuration file. This -is the file that the OpenEmbedded build system uses to configure the -kernel during the build. You can find and examine this file in the Build -Directory in ``tmp/work/``. The actual ``.config`` is located in the +Saving the selections updates the ``.config`` configuration file. This is the +file that the OpenEmbedded build system uses to configure the kernel during +the build. You can find and examine this file in the :term:`Build Directory` +in ``tmp/work/``. The actual ``.config`` is located in the area where the specific kernel is built. For example, if you were building a Linux Yocto kernel based on the ``linux-yocto-4.12`` kernel and you were building a QEMU image targeted for ``x86`` architecture, the ``.config`` file would be: -:: + +.. code-block:: none poky/build/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+gitAUTOINC+eda4d18... ...967-r0/linux-qemux86-standard-build/.config @@ -1273,8 +1107,7 @@ the ``.config`` file would be: Within the ``.config`` file, you can see the kernel settings. For example, the following entry shows that symmetric multi-processor -support is not set: -:: +support is not set:: # CONFIG_SMP is not set @@ -1289,11 +1122,8 @@ kernel layer. .. note:: - Be sure to make a copy of the - .config - file and do not just rename it. The build system needs an existing - .config - file from which to work. + Be sure to make a copy of the ``.config`` file and do not just rename it. + The build system needs an existing ``.config`` file from which to work. Creating a  ``defconfig`` File ------------------------------ @@ -1307,13 +1137,9 @@ which the OpenEmbedded build system can draw to create the final .. note:: - Out-of-the-box, the Yocto Project never ships a - defconfig - or - .config - file. The OpenEmbedded build system creates the final - .config - file used to configure the kernel. + Out-of-the-box, the Yocto Project never ships a ``defconfig`` or ``.config`` + file. The OpenEmbedded build system creates the final ``.config`` file used + to configure the kernel. To create a ``defconfig``, start with a complete, working Linux kernel ``.config`` file. Copy that file to the appropriate @@ -1322,10 +1148,9 @@ your layer's ``recipes-kernel/linux`` directory, and rename the copied file to "defconfig" (e.g. ``~/meta-mylayer/recipes-kernel/linux/linux-yocto/defconfig``). Then, add the following lines to the linux-yocto ``.bbappend`` file in your -layer: -:: +layer:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" SRC_URI += "file://defconfig" The :term:`SRC_URI` tells the build system how to search for the file, while the @@ -1335,21 +1160,16 @@ created to hold the configuration changes. .. note:: - The build system applies the configurations from the - defconfig + The build system applies the configurations from the ``defconfig`` file before applying any subsequent configuration fragments. The final kernel configuration is a combination of the configurations in - the - defconfig - file and any configuration fragments you provide. You need to realize - that if you have any configuration fragments, the build system - applies these on top of and after applying the existing defconfig - file configurations. - -For more information on configuring the kernel, see the "`Changing the -Configuration <#changing-the-configuration>`__" section. + the ``defconfig`` file and any configuration fragments you provide. You need + to realize that if you have any configuration fragments, the build system + applies these on top of and after applying the existing ``defconfig`` file + configurations. -.. _creating-config-fragments: +For more information on configuring the kernel, see the +":ref:`kernel-dev/common:changing the configuration`" section. Creating Configuration Fragments -------------------------------- @@ -1368,26 +1188,23 @@ appear in the ``.config`` file, which is in the :term:`Build Directory`. .. note:: - For more information about where the - .config - file is located, see the example in the - ":ref:`kernel-dev/kernel-dev-common:using \`\`menuconfig\`\``" + For more information about where the ``.config`` file is located, see the + example in the + ":ref:`kernel-dev/common:using \`\`menuconfig\`\``" section. It is simple to create a configuration fragment. One method is to use shell commands. For example, issuing the following from the shell creates a configuration fragment file named ``my_smp.cfg`` that enables -multi-processor support within the kernel: -:: +multi-processor support within the kernel:: $ echo "CONFIG_SMP=y" >> my_smp.cfg .. note:: - All configuration fragment files must use the - .cfg - extension in order for the OpenEmbedded build system to recognize - them as a configuration fragment. + All configuration fragment files must use the ``.cfg`` extension in order + for the OpenEmbedded build system to recognize them as a configuration + fragment. Another method is to create a configuration fragment using the differences between two configuration files: one previously created and @@ -1396,42 +1213,38 @@ saved, and one freshly created using the ``menuconfig`` tool. To create a configuration fragment using this method, follow these steps: -1. *Complete a Build Through Kernel Configuration:* Complete a build at - least through the kernel configuration task as follows: - :: +#. *Complete a Build Through Kernel Configuration:* Complete a build at + least through the kernel configuration task as follows:: $ bitbake linux-yocto -c kernel_configme -f This step ensures that you create a - ``.config`` file from a known state. Because situations exist where + ``.config`` file from a known state. Because there are situations where your build state might become unknown, it is best to run this task prior to starting ``menuconfig``. -2. *Launch menuconfig:* Run the ``menuconfig`` command: - :: +#. *Launch menuconfig:* Run the ``menuconfig`` command:: $ bitbake linux-yocto -c menuconfig -3. *Create the Configuration Fragment:* Run the ``diffconfig`` command +#. *Create the Configuration Fragment:* Run the ``diffconfig`` command to prepare a configuration fragment. The resulting file ``fragment.cfg`` is placed in the ``${``\ :term:`WORKDIR`\ ``}`` - directory: - :: + directory:: $ bitbake linux-yocto -c diffconfig The ``diffconfig`` command creates a file that is a list of Linux kernel -``CONFIG_`` assignments. See the "`Changing the -Configuration <#changing-the-configuration>`__" section for additional +``CONFIG_`` assignments. See the +":ref:`kernel-dev/common:changing the configuration`" section for additional information on how to use the output as a configuration fragment. .. note:: You can also use this method to create configuration fragments for a - BSP. See the " - BSP Descriptions - " section for more information. + BSP. See the ":ref:`kernel-dev/advanced:bsp descriptions`" + section for more information. Where do you put your configuration fragment files? You can place these files in an area pointed to by @@ -1443,18 +1256,16 @@ options in a file called ``myconfig.cfg``. If you put that file inside a directory named ``linux-yocto`` that resides in the same directory as the kernel's append file within your layer and then add the following statements to the kernel's append file, those configuration options will -be picked up and applied when the kernel is built: -:: +be picked up and applied when the kernel is built:: - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" + FILESEXTRAPATHS:prepend := "${THISDIR}/${PN}:" SRC_URI += "file://myconfig.cfg" As mentioned earlier, you can group related configurations into multiple -files and name them all in the ``SRC_URI`` statement as well. For +files and name them all in the :term:`SRC_URI` statement as well. For example, you could group separate configurations specifically for Ethernet and graphics into their own files and add those by using a -``SRC_URI`` statement like the following in your append file: -:: +:term:`SRC_URI` statement like the following in your append file:: SRC_URI += "file://myconfig.cfg \ file://eth.cfg \ @@ -1465,8 +1276,7 @@ Validating Configuration You can use the :ref:`ref-tasks-kernel_configcheck` -task to provide configuration validation: -:: +task to provide configuration validation:: $ bitbake linux-yocto -c kernel_configcheck -f @@ -1476,11 +1286,12 @@ when you override a policy configuration in a hardware configuration fragment. In order to run this task, you must have an existing ``.config`` file. -See the ":ref:`kernel-dev/kernel-dev-common:using \`\`menuconfig\`\``" section for +See the ":ref:`kernel-dev/common:using \`\`menuconfig\`\``" section for information on how to create a configuration file. -Following is sample output from the ``do_kernel_configcheck`` task: -:: +Here is sample output from the :ref:`ref-tasks-kernel_configcheck` task: + +.. code-block:: none Loading cache: 100% |########################################################| Time: 0:00:00 Loaded 1275 entries from dependency cache. @@ -1548,7 +1359,7 @@ and tasks until they produce no warnings. For more information on how to use the ``menuconfig`` tool, see the -:ref:`kernel-dev/kernel-dev-common:using \`\`menuconfig\`\`` section. +:ref:`kernel-dev/common:using \`\`menuconfig\`\`` section. Fine-Tuning the Kernel Configuration File ----------------------------------------- @@ -1558,12 +1369,12 @@ possible by reading the output of the kernel configuration fragment audit, noting any issues, making changes to correct the issues, and then repeating. -As part of the kernel build process, the ``do_kernel_configcheck`` task +As part of the kernel build process, the :ref:`ref-tasks-kernel_configcheck` task runs. This task validates the kernel configuration by checking the final ``.config`` file against the input files. During the check, the task produces warning messages for the following issues: -- Requested options that did not make the final ``.config`` file. +- Requested options that did not make it into the final ``.config`` file. - Configuration items that appear twice in the same configuration fragment. @@ -1577,10 +1388,8 @@ produces warning messages for the following issues: .. note:: - The - do_kernel_configcheck - task can also optionally report if an option is overridden during - processing. + The :ref:`ref-tasks-kernel_configcheck` task can also optionally report if + an option is overridden during processing. For each output warning, a message points to the file that contains a list of the options and a pointer to the configuration fragment that @@ -1589,19 +1398,18 @@ configuration. To streamline the configuration, do the following: -1. *Use a Working Configuration:* Start with a full configuration that +#. *Use a Working Configuration:* Start with a full configuration that you know works. Be sure the configuration builds and boots successfully. Use this configuration file as your baseline. -2. *Run Configure and Check Tasks:* Separately run the - ``do_kernel_configme`` and ``do_kernel_configcheck`` tasks: - :: +#. *Run Configure and Check Tasks:* Separately run the + :ref:`ref-tasks-kernel_configme` and :ref:`ref-tasks-kernel_configcheck` tasks:: $ bitbake linux-yocto -c kernel_configme -f $ bitbake linux-yocto -c kernel_configcheck -f -3. *Process the Results:* Take the resulting list of files from the - ``do_kernel_configcheck`` task warnings and do the following: +#. *Process the Results:* Take the resulting list of files from the + :ref:`ref-tasks-kernel_configcheck` task warnings and do the following: - Drop values that are redefined in the fragment but do not change the final ``.config`` file. @@ -1613,9 +1421,9 @@ To streamline the configuration, do the following: - Remove repeated and invalid options. -4. *Re-Run Configure and Check Tasks:* After you have worked through the +#. *Re-Run Configure and Check Tasks:* After you have worked through the output of the kernel configuration audit, you can re-run the - ``do_kernel_configme`` and ``do_kernel_configcheck`` tasks to see the + :ref:`ref-tasks-kernel_configme` and :ref:`ref-tasks-kernel_configcheck` tasks to see the results of your changes. If you have more issues, you can deal with them as described in the previous step. @@ -1627,10 +1435,9 @@ Expanding Variables =================== Sometimes it is helpful to determine what a variable expands to during a -build. You can do examine the values of variables by examining the +build. You can examine the values of variables by examining the output of the ``bitbake -e`` command. The output is long and is more -easily managed in a text file, which allows for easy searches: -:: +easily managed in a text file, which allows for easy searches:: $ bitbake -e virtual/kernel > some_text_file @@ -1642,35 +1449,32 @@ Working with a "Dirty" Kernel Version String ============================================ If you build a kernel image and the version string has a "+" or a -"-dirty" at the end, uncommitted modifications exist in the kernel's +"-dirty" at the end, it means there are uncommitted modifications in the kernel's source directory. Follow these steps to clean up the version string: -1. *Discover the Uncommitted Changes:* Go to the kernel's locally cloned +#. *Discover the Uncommitted Changes:* Go to the kernel's locally cloned Git repository (source directory) and use the following Git command - to list the files that have been changed, added, or removed: - :: + to list the files that have been changed, added, or removed:: $ git status -2. *Commit the Changes:* You should commit those changes to the kernel +#. *Commit the Changes:* You should commit those changes to the kernel source tree regardless of whether or not you will save, export, or - use the changes: - :: + use the changes:: $ git add $ git commit -s -a -m "getting rid of -dirty" -3. *Rebuild the Kernel Image:* Once you commit the changes, rebuild the +#. *Rebuild the Kernel Image:* Once you commit the changes, rebuild the kernel. Depending on your particular kernel development workflow, the commands you use to rebuild the kernel might differ. For information on building the kernel image when using ``devtool``, see the - ":ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" + ":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" section. For - information on building the kernel image when using Bitbake, see the - "`Using Traditional Kernel Development to Patch the - Kernel <#using-traditional-kernel-development-to-patch-the-kernel>`__" + information on building the kernel image when using BitBake, see the + ":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" section. Working With Your Own Sources @@ -1687,34 +1491,30 @@ Maintaining format compatibility facilitates converging with linux-yocto on a future, mutually-supported kernel version. To help you use your own sources, the Yocto Project provides a -linux-yocto custom recipe (``linux-yocto-custom.bb``) that uses -``kernel.org`` sources and the Yocto Project Linux kernel tools for -managing kernel Metadata. You can find this recipe in the ``poky`` Git -repository of the Yocto Project :yocto_git:`Source Repository <>` -at: -:: - - poky/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb +linux-yocto custom recipe that uses ``kernel.org`` sources and +the Yocto Project Linux kernel tools for managing kernel Metadata. +You can find this recipe in the ``poky`` Git repository: +:yocto_git:`meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb +</poky/tree/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb>`. Here are some basic steps you can use to work with your own sources: -1. *Create a Copy of the Kernel Recipe:* Copy the +#. *Create a Copy of the Kernel Recipe:* Copy the ``linux-yocto-custom.bb`` recipe to your layer and give it a meaningful name. The name should include the version of the Yocto Linux kernel you are using (e.g. ``linux-yocto-myproject_4.12.bb``, where "4.12" is the base version of the Linux kernel with which you would be working). -2. *Create a Directory for Your Patches:* In the same directory inside +#. *Create a Directory for Your Patches:* In the same directory inside your layer, create a matching directory to store your patches and configuration files (e.g. ``linux-yocto-myproject``). -3. *Ensure You Have Configurations:* Make sure you have either a +#. *Ensure You Have Configurations:* Make sure you have either a ``defconfig`` file or configuration fragment files in your layer. When you use the ``linux-yocto-custom.bb`` recipe, you must specify a configuration. If you do not have a ``defconfig`` file, you can run - the following: - :: + the following:: $ make defconfig @@ -1726,7 +1526,7 @@ Here are some basic steps you can use to work with your own sources: Running the ``make defconfig`` command results in the default configuration for your architecture as defined by your kernel. - However, no guarantee exists that this configuration is valid for + However, there is no guarantee that this configuration is valid for your use case, or that your board will even boot. This is particularly true for non-x86 architectures. @@ -1735,15 +1535,15 @@ Here are some basic steps you can use to work with your own sources: ``arch/arm/configs`` and use the one that is the best starting point for your board). -4. *Edit the Recipe:* Edit the following variables in your recipe as +#. *Edit the Recipe:* Edit the following variables in your recipe as appropriate for your project: - :term:`SRC_URI`: The - ``SRC_URI`` should specify a Git repository that uses one of the + :term:`SRC_URI` should specify a Git repository that uses one of the supported Git fetcher protocols (i.e. ``file``, ``git``, ``http``, - and so forth). The ``SRC_URI`` variable should also specify either + and so forth). The :term:`SRC_URI` variable should also specify either a ``defconfig`` file or some configuration fragment files. The - skeleton recipe provides an example ``SRC_URI`` as a syntax + skeleton recipe provides an example :term:`SRC_URI` as a syntax reference. - :term:`LINUX_VERSION`: @@ -1761,14 +1561,16 @@ Here are some basic steps you can use to work with your own sources: indicate to the OpenEmbedded build system that the recipe has changed. - - :term:`PV`: The default ``PV`` + - :term:`PV`: The default :term:`PV` assignment is typically adequate. It combines the - ``LINUX_VERSION`` with the Source Control Manager (SCM) revision + :term:`LINUX_VERSION` with the Source Control Manager (SCM) revision as derived from the :term:`SRCPV` variable. The combined results are a string with the following - form: - 3.19.11+git1+68a635bf8dfb64b02263c1ac80c948647cc76d5f_1+218bd8d2022b9852c60d32f0d770931e3cf343e2 - While lengthy, the extra verbosity in ``PV`` helps ensure you are + form:: + + 3.19.11+git1+68a635bf8dfb64b02263c1ac80c948647cc76d5f_1+218bd8d2022b9852c60d32f0d770931e3cf343e2 + + While lengthy, the extra verbosity in :term:`PV` helps ensure you are using the exact sources from which you intend to build. - :term:`COMPATIBLE_MACHINE`: @@ -1778,12 +1580,15 @@ Here are some basic steps you can use to work with your own sources: triggers an explicit build failure. You must change it to match a list of the machines that your new recipe supports. For example, to support the ``qemux86`` and ``qemux86-64`` machines, use the - following form: COMPATIBLE_MACHINE = "qemux86|qemux86-64" + following form:: + + COMPATIBLE_MACHINE = "qemux86|qemux86-64" -5. *Customize Your Recipe as Needed:* Provide further customizations to +#. *Customize Your Recipe as Needed:* Provide further customizations to your recipe as needed just as you would customize an existing - linux-yocto recipe. See the "`Modifying an Existing - Recipe <#modifying-an-existing-recipe>`__" section for information. + linux-yocto recipe. See the + ":ref:`ref-manual/devtool-reference:modifying an existing recipe`" section + for information. Working with Out-of-Tree Modules ================================ @@ -1813,7 +1618,8 @@ is running that image. Prior to attempting to build the out-of-tree modules, you need to be on the target as root and you need to change to the ``/usr/src/kernel`` directory. Next, ``make`` the scripts: -:: + +.. code-block:: none # cd /usr/src/kernel # make scripts @@ -1834,10 +1640,9 @@ Linux kernel sources, if you need an external kernel module, the create your own out-of-tree Linux kernel module recipe. This template recipe is located in the ``poky`` Git repository of the -Yocto Project :yocto_git:`Source Repository <>` at: -:: - - poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb +Yocto Project: +:yocto_git:`meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb +</poky/tree/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb>`. To get started, copy this recipe to your layer and give it a meaningful name (e.g. ``mymodule_1.0.bb``). In the same directory, create a new @@ -1856,29 +1661,26 @@ Typically, you will need to set the following variables: Depending on the build system used by the module sources, you might need to make some adjustments. For example, a typical module ``Makefile`` -looks much like the one provided with the ``hello-mod`` template: -:: +looks much like the one provided with the ``hello-mod`` template:: obj-m := hello.o SRC := $(shell pwd) all: - $(MAKE) -C $(KERNEL_SRC) M=$(SRC) + $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install: - $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install + $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install ... The important point to note here is the :term:`KERNEL_SRC` variable. The -:ref:`module <ref-classes-module>` class sets this variable and the -:term:`KERNEL_PATH` variable to -``${STAGING_KERNEL_DIR}`` with the necessary Linux kernel build -information to build modules. If your module ``Makefile`` uses a -different variable, you might want to override the -:ref:`ref-tasks-compile` step, or +:ref:`ref-classes-module` class sets this variable and the :term:`KERNEL_PATH` +variable to ``${STAGING_KERNEL_DIR}`` with the necessary Linux kernel build +information to build modules. If your module ``Makefile`` uses a different +variable, you might want to override the :ref:`ref-tasks-compile` step, or create a patch to the ``Makefile`` to work with the more typical -``KERNEL_SRC`` or ``KERNEL_PATH`` variables. +:term:`KERNEL_SRC` or :term:`KERNEL_PATH` variables. After you have prepared your recipe, you will likely want to include the module in your images. To do this, see the documentation for the @@ -1894,8 +1696,7 @@ them appropriately for your machine configuration file: - :term:`MACHINE_EXTRA_RRECOMMENDS` Modules are often not required for boot and can be excluded from certain -build configurations. The following allows for the most flexibility: -:: +build configurations. The following allows for the most flexibility:: MACHINE_EXTRA_RRECOMMENDS += "kernel-module-mymodule" @@ -1919,53 +1720,46 @@ tree. Using Git is an efficient way to see what has changed in the tree. What Changed in a Kernel? ------------------------- -Following are a few examples that show how to use Git commands to +Here are a few examples that show how to use Git commands to examine changes. These examples are by no means the only way to see changes. .. note:: - In the following examples, unless you provide a commit range, - kernel.org + In the following examples, unless you provide a commit range, ``kernel.org`` history is blended with Yocto Project kernel changes. You can form ranges by using branch names from the kernel tree as the upper and lower commit markers with the Git commands. You can see the branch names through the web interface to the Yocto Project source - repositories at - . + repositories at :yocto_git:`/`. To see a full range of the changes, use the ``git whatchanged`` command -and specify a commit range for the branch (commit\ ``..``\ commit). +and specify a commit range for the branch (`commit`\ ``..``\ `commit`). Here is an example that looks at what has changed in the ``emenlow`` branch of the ``linux-yocto-3.19`` kernel. The lower commit range is the commit associated with the ``standard/base`` branch, while the upper commit range is the commit associated with the ``standard/emenlow`` -branch. -:: +branch:: $ git whatchanged origin/standard/base..origin/standard/emenlow -To see short, one line summaries of changes use the ``git log`` command: -:: +To see short, one line summaries of changes use the ``git log`` command:: $ git log --oneline origin/standard/base..origin/standard/emenlow -Use this command to see code differences for the changes: -:: +Use this command to see code differences for the changes:: $ git diff origin/standard/base..origin/standard/emenlow Use this command to see the commit log messages and the text -differences: -:: +differences:: $ git show origin/standard/base..origin/standard/emenlow Use this command to create individual patches for each change. Here is -an example that that creates patch files for each commit and places them -in your ``Documents`` directory: -:: +an example that creates patch files for each commit and places them +in your ``Documents`` directory:: $ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow @@ -1974,15 +1768,13 @@ Showing a Particular Feature or Branch Change Tags in the Yocto Project kernel tree divide changes for significant features or branches. The ``git show`` tag command shows changes based -on a tag. Here is an example that shows ``systemtap`` changes: -:: +on a tag. Here is an example that shows ``systemtap`` changes:: $ git show systemtap You can use the ``git branch --contains`` tag command to show the branches that contain a particular feature. This command shows -the branches that contain the ``systemtap`` feature: -:: +the branches that contain the ``systemtap`` feature:: $ git branch --contains systemtap @@ -1990,8 +1782,8 @@ Adding Recipe-Space Kernel Features =================================== You can add kernel features in the -`recipe-space <#recipe-space-metadata>`__ by using the -:term:`KERNEL_FEATURES` +:ref:`recipe-space <kernel-dev/advanced:recipe-space metadata>` +by using the :term:`KERNEL_FEATURES` variable and by specifying the feature's ``.scc`` file path in the :term:`SRC_URI` statement. When you add features using this method, the OpenEmbedded build system checks to @@ -2000,31 +1792,31 @@ build stops. Kernel features are the last elements processed for configuring and patching the kernel. Therefore, adding features in this manner is a way to enforce specific features are present and enabled without needing to do a full audit of any other layer's additions to the -``SRC_URI`` statement. +:term:`SRC_URI` statement. You add a kernel feature by providing the feature as part of the -``KERNEL_FEATURES`` variable and by providing the path to the feature's +:term:`KERNEL_FEATURES` variable and by providing the path to the feature's ``.scc`` file, which is relative to the root of the kernel Metadata. The OpenEmbedded build system searches all forms of kernel Metadata on the -``SRC_URI`` statement regardless of whether the Metadata is in the +:term:`SRC_URI` statement regardless of whether the Metadata is in the "kernel-cache", system kernel Metadata, or a recipe-space Metadata (i.e. -part of the kernel recipe). See the "`Kernel Metadata -Location <#kernel-metadata-location>`__" section for additional -information. +part of the kernel recipe). See the +":ref:`kernel-dev/advanced:kernel metadata location`" section for +additional information. -When you specify the feature's ``.scc`` file on the ``SRC_URI`` +When you specify the feature's ``.scc`` file on the :term:`SRC_URI` statement, the OpenEmbedded build system adds the directory of that ``.scc`` file along with all its subdirectories to the kernel feature search path. Because subdirectories are searched, you can reference a -single ``.scc`` file in the ``SRC_URI`` statement to reference multiple +single ``.scc`` file in the :term:`SRC_URI` statement to reference multiple kernel features. Consider the following example that adds the "test.scc" feature to the build. -1. *Create the Feature File:* Create a ``.scc`` file and locate it just +#. *Create the Feature File:* Create a ``.scc`` file and locate it just as you would any other patch file, ``.cfg`` file, or fetcher item you - specify in the ``SRC_URI`` statement. + specify in the :term:`SRC_URI` statement. .. note:: @@ -2037,8 +1829,7 @@ build. searched during the build as potential feature directories. Continuing with the example, suppose the "test.scc" feature you are - adding has a ``test.scc`` file in the following directory: - :: + adding has a ``test.scc`` file in the following directory:: my_recipe | @@ -2051,21 +1842,19 @@ build. ``linux-yocto`` directory has both the feature ``test.scc`` file and a similarly named configuration fragment file ``test.cfg``. -2. *Add the Feature File to SRC_URI:* Add the ``.scc`` file to the - recipe's ``SRC_URI`` statement: - :: +#. *Add the Feature File to SRC_URI:* Add the ``.scc`` file to the + recipe's :term:`SRC_URI` statement:: - SRC_URI_append = " file://test.scc" + SRC_URI += "file://test.scc" The leading space before the path is important as the path is appended to the existing path. -3. *Specify the Feature as a Kernel Feature:* Use the - ``KERNEL_FEATURES`` statement to specify the feature as a kernel - feature: - :: +#. *Specify the Feature as a Kernel Feature:* Use the + :term:`KERNEL_FEATURES` statement to specify the feature as a kernel + feature:: - KERNEL_FEATURES_append = " test.scc" + KERNEL_FEATURES += "test.scc" The OpenEmbedded build system processes the kernel feature when it builds the kernel. @@ -2073,6 +1862,5 @@ build. .. note:: If other features are contained below "test.scc", then their - directories are relative to the directory containing the - test.scc + directories are relative to the directory containing the ``test.scc`` file. diff --git a/documentation/kernel-dev/kernel-dev-concepts-appx.rst b/documentation/kernel-dev/concepts-appx.rst index 04cb1172b2..6a2fe4bb0b 100644 --- a/documentation/kernel-dev/kernel-dev-concepts-appx.rst +++ b/documentation/kernel-dev/concepts-appx.rst @@ -1,17 +1,15 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ************************ Advanced Kernel Concepts ************************ -.. _kernel-big-picture: - Yocto Project Kernel Development and Maintenance ================================================ Kernels available through the Yocto Project (Yocto Linux kernels), like other kernels, are based off the Linux kernel releases from -http://www.kernel.org. At the beginning of a major Linux kernel +https://www.kernel.org. At the beginning of a major Linux kernel development cycle, the Yocto Project team chooses a Linux kernel based on factors such as release timing, the anticipated release timing of final upstream ``kernel.org`` versions, and Yocto Project feature @@ -37,7 +35,7 @@ Yocto Project Linux kernel that caters to specific embedded designer needs for targeted hardware. You can find a web interface to the Yocto Linux kernels in the -:ref:`overview-manual/overview-manual-development-environment:yocto project source repositories` +:ref:`overview-manual/development-environment:yocto project source repositories` at :yocto_git:`/`. If you look at the interface, you will see to the left a grouping of Git repositories titled "Yocto Linux Kernel". Within this group, you will find several Linux Yocto kernels developed @@ -73,7 +71,7 @@ and included with Yocto Project releases: and configurations for the linux-yocto kernel tree. This repository is useful when working on the linux-yocto kernel. For more information on this "Advanced Kernel Metadata", see the - ":doc:`kernel-dev-advanced`" Chapter. + ":doc:`/kernel-dev/advanced`" Chapter. - *linux-yocto-dev:* A development kernel based on the latest upstream release candidate available. @@ -119,7 +117,7 @@ upstream Linux kernel development and are managed by the Yocto Project team's Yocto Linux kernel development strategy. It is the Yocto Project team's policy to not back-port minor features to the released Yocto Linux kernel. They only consider back-porting significant technological -jumps DASH and, that is done after a complete gap analysis. The reason +jumps --- and, that is done after a complete gap analysis. The reason for this policy is that back-porting any small to medium sized change from an evolving Linux kernel can easily create mismatches, incompatibilities and very subtle errors. @@ -129,7 +127,7 @@ cutting edge Yocto Linux kernel that mixes forward ports of existing Linux kernel features and significant and critical new functionality. Forward porting Linux kernel functionality into the Yocto Linux kernels available through the Yocto Project can be thought of as a "micro -uprev." The many "micro uprevs" produce a Yocto Linux kernel version +uprev". The many "micro uprevs" produce a Yocto Linux kernel version with a mix of important new mainline, non-mainline, BSP developments and feature integrations. This Yocto Linux kernel gives insight into new features and allows focused amounts of testing to be done on the kernel, @@ -160,10 +158,9 @@ implemented by the Yocto Project team using the Source Code Manager but, Git continues to grow in popularity and supports many different work flows, front-ends and management techniques. - - You can find documentation on Git at - http://git-scm.com/documentation. You can also get an - introduction to Git as it applies to the Yocto Project in the - ":ref:`overview-manual/overview-manual-development-environment:git`" section in the Yocto Project + - You can find documentation on Git at https://git-scm.com/doc. You can + also get an introduction to Git as it applies to the Yocto Project in the + ":ref:`overview-manual/development-environment:git`" section in the Yocto Project Overview and Concepts Manual. The latter reference provides an overview of Git and presents a minimal set of Git commands that allows you to be functional using Git. You can use as much, or as @@ -214,9 +211,9 @@ view, there is a linear path that travels from the baseline ``kernel.org``, through a select group of features and ends with their BSP-specific commits. In other words, the divisions of the kernel are transparent and are not relevant to the developer on a day-to-day basis. -From the developer's perspective, this path is the "master" branch in -Git terms. The developer does not need to be aware of the existence of -any other branches at all. Of course, value exists in the having these +From the developer's perspective, this path is the development branch. +The developer does not need to be aware of the existence of +any other branches at all. Of course, it can make sense to have these branches in the tree, should a person decide to explore them. For example, a comparison between two BSPs at either the commit level or at the line-by-line code ``diff`` level is now a trivial operation. @@ -224,7 +221,7 @@ the line-by-line code ``diff`` level is now a trivial operation. The following illustration shows the conceptual Yocto Linux kernel. .. image:: figures/kernel-architecture-overview.png - :align: center + :width: 100% In the illustration, the "Kernel.org Branch Point" marks the specific spot (or Linux kernel release) from which the Yocto Linux kernel is @@ -260,8 +257,8 @@ Yocto Linux kernel needed for any given set of requirements. Keep in mind the figure does not take into account all the supported Yocto Linux kernels, but rather shows a single generic kernel just for conceptual purposes. Also keep in mind that this structure - represents the Yocto Project - Source Repositories + represents the + :ref:`overview-manual/development-environment:yocto project source repositories` that are either pulled from during the build or established on the host development system prior to the build by either cloning a particular kernel's Git repository or by downloading and unpacking a @@ -296,13 +293,13 @@ ways: - *Files Accessed While using devtool:* ``devtool``, which is available with the Yocto Project, is the preferred method by which to - modify the kernel. See the ":ref:`kernel-dev/kernel-dev-intro:kernel modification workflow`" section. + modify the kernel. See the ":ref:`kernel-dev/intro:kernel modification workflow`" section. - *Cloned Repository:* If you are working in the kernel all the time, you probably would want to set up your own local Git repository of the Yocto Linux kernel tree. For information on how to clone a Yocto Linux kernel Git repository, see the - ":ref:`kernel-dev/kernel-dev-common:preparing the build host to work on the kernel`" + ":ref:`kernel-dev/common:preparing the build host to work on the kernel`" section. - *Temporary Source Files from a Build:* If you just need to make some @@ -321,20 +318,20 @@ tree specific to your kernel from which to generate the new kernel image. The following figure shows the temporary file structure created on your -host system when you build the kernel using Bitbake. This -:term:`Build Directory` contains all the -source files used during the build. +host system when you build the kernel using BitBake. This +:term:`Build Directory` contains all the source files used during the build. .. image:: figures/kernel-overview-2-generic.png :align: center + :width: 70% Again, for additional information on the Yocto Project kernel's architecture and its branching strategy, see the -":ref:`kernel-dev/kernel-dev-concepts-appx:yocto linux kernel architecture and branching strategies`" +":ref:`kernel-dev/concepts-appx:yocto linux kernel architecture and branching strategies`" section. You can also reference the -":ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" +":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" and -":ref:`kernel-dev/kernel-dev-common:using traditional kernel development to patch the kernel`" +":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" sections for detailed example that modifies the kernel. Determining Hardware and Non-Hardware Features for the Kernel Configuration Audit Phase @@ -344,7 +341,7 @@ This section describes part of the kernel configuration audit phase that most developers can ignore. For general information on kernel configuration including ``menuconfig``, ``defconfig`` files, and configuration fragments, see the -":ref:`kernel-dev/kernel-dev-common:configuring the kernel`" section. +":ref:`kernel-dev/common:configuring the kernel`" section. During this part of the audit phase, the contents of the final ``.config`` file are compared against the fragments specified by the @@ -362,8 +359,7 @@ To determine whether or not a given option is "hardware" or "non-hardware", the kernel Metadata in ``yocto-kernel-cache`` contains files that classify individual or groups of options as either hardware or non-hardware. To better show this, consider a situation where the -``yocto-kernel-cache`` contains the following files: -:: +``yocto-kernel-cache`` contains the following files:: yocto-kernel-cache/features/drm-psb/hardware.cfg yocto-kernel-cache/features/kgdb/hardware.cfg @@ -383,8 +379,7 @@ or non-hardware. To better show this, consider a situation where the yocto-kernel-cache/ktypes/base/hardware.kcf yocto-kernel-cache/bsp/qemu-ppc32/hardware.kcf -The following list -provides explanations for the various files: +Here are explanations for the various files: - ``hardware.kcf``: Specifies a list of kernel Kconfig files that contain hardware options only. @@ -403,8 +398,7 @@ provides explanations for the various files: (i.e. ``hardware.kcf`` or ``non-hardware.kcf``). Here is a specific example using the -``kernel-cache/bsp/mti-malta32/hardware.cfg``: -:: +``kernel-cache/bsp/mti-malta32/hardware.cfg``:: CONFIG_SERIAL_8250 CONFIG_SERIAL_8250_CONSOLE diff --git a/documentation/kernel-dev/kernel-dev-faq.rst b/documentation/kernel-dev/faq.rst index b5e6a84eba..4dffa90dbd 100644 --- a/documentation/kernel-dev/kernel-dev-faq.rst +++ b/documentation/kernel-dev/faq.rst @@ -1,46 +1,44 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ********************** Kernel Development FAQ ********************** -.. _kernel-dev-faq-section: - Common Questions and Solutions ============================== -The following lists some solutions for common questions. +Here are some solutions for common questions. How do I use my own Linux kernel ``.config`` file? -------------------------------------------------- Refer to the -":ref:`kernel-dev/kernel-dev-common:changing the configuration`" +":ref:`kernel-dev/common:changing the configuration`" section for information. How do I create configuration fragments? ---------------------------------------- A: Refer to the -":ref:`kernel-dev/kernel-dev-common:creating configuration fragments`" +":ref:`kernel-dev/common:creating configuration fragments`" section for information. How do I use my own Linux kernel sources? ----------------------------------------- Refer to the -":ref:`kernel-dev/kernel-dev-common:working with your own sources`" +":ref:`kernel-dev/common:working with your own sources`" section for information. -How do I install/not-install the kernel image on the rootfs? ------------------------------------------------------------- +How do I install/not-install the kernel image on the root filesystem? +--------------------------------------------------------------------- The kernel image (e.g. ``vmlinuz``) is provided by the ``kernel-image`` package. Image recipes depend on ``kernel-base``. To specify whether or not the kernel image is installed in the generated -root filesystem, override ``RDEPENDS_kernel-base`` to include or not +root filesystem, override ``RRECOMMENDS:${KERNEL_PACKAGE_NAME}-base`` to include or not include "kernel-image". See the -":ref:`dev-manual/dev-manual-common-tasks:using .bbappend files in your layer`" +":ref:`dev-manual/layers:appending other layers metadata with your layer`" section in the Yocto Project Development Tasks Manual for information on how to use an append file to override metadata. @@ -50,32 +48,29 @@ How do I install a specific kernel module? Linux kernel modules are packaged individually. To ensure a specific kernel module is included in an image, include it in the -appropriate machine -:term:`RRECOMMENDS` variable. +appropriate machine :term:`RRECOMMENDS` variable. These other variables are useful for installing specific modules: -:term:`MACHINE_ESSENTIAL_EXTRA_RDEPENDS` -:term:`MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS` -:term:`MACHINE_EXTRA_RDEPENDS` -:term:`MACHINE_EXTRA_RRECOMMENDS` +- :term:`MACHINE_ESSENTIAL_EXTRA_RDEPENDS` +- :term:`MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS` +- :term:`MACHINE_EXTRA_RDEPENDS` +- :term:`MACHINE_EXTRA_RRECOMMENDS` + For example, set the following in the ``qemux86.conf`` file to include the ``ab123`` kernel modules with images built for the ``qemux86`` -machine: -:: +machine:: MACHINE_EXTRA_RRECOMMENDS += "kernel-module-ab123" -For more -information, see the "`Incorporating Out-of-Tree -Modules <#incorporating-out-of-tree-modules>`__" section. +For more information, see the +":ref:`kernel-dev/common:incorporating out-of-tree modules`" section. How do I change the Linux kernel command line? ---------------------------------------------- The Linux kernel command line is -typically specified in the machine config using the ``APPEND`` variable. +typically specified in the machine config using the :term:`APPEND` variable. For example, you can add some helpful debug information doing the -following: -:: +following:: APPEND += "printk.time=y initcall_debug debug" diff --git a/documentation/kernel-dev/history.rst b/documentation/kernel-dev/history.rst deleted file mode 100644 index 3ffb7eacb8..0000000000 --- a/documentation/kernel-dev/history.rst +++ /dev/null @@ -1,58 +0,0 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK - -*********************** -Manual Revision History -*********************** - -.. list-table:: - :widths: 10 15 40 - :header-rows: 1 - - * - Revision - - Date - - Note - * - 1.4 - - April 2013 - - The initial document released with the Yocto Project 1.4 Release - * - 1.5 - - October 2013 - - Released with the Yocto Project 1.5 Release. - * - 1.6 - - April 2014 - - Released with the Yocto Project 1.6 Release. - * - 1.7 - - October 2014 - - Released with the Yocto Project 1.7 Release. - * - 1.8 - - April 2015 - - Released with the Yocto Project 1.8 Release. - * - 2.0 - - October 2015 - - Released with the Yocto Project 2.0 Release. - * - 2.1 - - April 2016 - - Released with the Yocto Project 2.1 Release. - * - 2.2 - - October 2016 - - Released with the Yocto Project 2.2 Release. - * - 2.3 - - May 2017 - - Released with the Yocto Project 2.3 Release. - * - 2.4 - - October 2017 - - Released with the Yocto Project 2.4 Release. - * - 2.5 - - May 2018 - - Released with the Yocto Project 2.5 Release. - * - 2.6 - - November 2018 - - Released with the Yocto Project 2.6 Release. - * - 2.7 - - May 2019 - - Released with the Yocto Project 2.7 Release. - * - 3.0 - - October 2019 - - Released with the Yocto Project 3.0 Release. - * - 3.1 - - April 2020 - - Released with the Yocto Project 3.1 Release. diff --git a/documentation/kernel-dev/kernel-dev.rst b/documentation/kernel-dev/index.rst index 332e089b03..bd20e371e0 100644 --- a/documentation/kernel-dev/kernel-dev.rst +++ b/documentation/kernel-dev/index.rst @@ -1,4 +1,4 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ============================================= Yocto Project Linux Kernel Development Manual @@ -10,12 +10,11 @@ Yocto Project Linux Kernel Development Manual :caption: Table of Contents :numbered: - kernel-dev-intro - kernel-dev-common - kernel-dev-advanced - kernel-dev-concepts-appx - kernel-dev-maint-appx - kernel-dev-faq - history + intro + common + advanced + concepts-appx + maint-appx + faq .. include:: /boilerplate.rst diff --git a/documentation/kernel-dev/kernel-dev-intro.rst b/documentation/kernel-dev/intro.rst index 21d43d5e80..a663733a1d 100644 --- a/documentation/kernel-dev/kernel-dev-intro.rst +++ b/documentation/kernel-dev/intro.rst @@ -1,11 +1,9 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ************ Introduction ************ -.. _kernel-dev-overview: - Overview ======== @@ -23,13 +21,13 @@ Each Yocto Project release has a set of Yocto Linux kernel recipes, whose Git repositories you can view in the Yocto :yocto_git:`Source Repositories <>` under the "Yocto Linux Kernel" heading. New recipes for the release track the latest Linux kernel -upstream developments from http://www.kernel.org> and introduce +upstream developments from https://www.kernel.org and introduce newly-supported platforms. Previous recipes in the release are refreshed and supported for at least one additional Yocto Project release. As they align, these previous releases are updated to include the latest from the Long Term Support Initiative (LTSI) project. You can learn more -about Yocto Linux kernels and LTSI in the ":ref:`Yocto Project Kernel -Development and Maintenance <kernel-big-picture>`" section. +about Yocto Linux kernels and LTSI in the +":ref:`kernel-dev/concepts-appx:yocto project kernel development and maintenance`" section. Also included is a Yocto Linux kernel development recipe (``linux-yocto-dev.bb``) should you want to work with the very latest in @@ -37,8 +35,8 @@ upstream Yocto Linux kernel development and kernel Metadata development. .. note:: - For more on Yocto Linux kernels, see the " - Yocto Project Kernel Development and Maintenance + For more on Yocto Linux kernels, see the + ":ref:`kernel-dev/concepts-appx:yocto project kernel development and maintenance`" section. The Yocto Project also provides a powerful set of kernel tools for @@ -68,33 +66,31 @@ from the continual kernel integration and testing performed during development of the Yocto Project. If, instead, you have a very specific Linux kernel source tree and are -unable to align with one of the official Yocto Linux kernel recipes, an -alternative exists by which you can use the Yocto Project Linux kernel -tools with your own kernel sources. +unable to align with one of the official Yocto Linux kernel recipes, +you have a way to use the Yocto Project Linux kernel tools with your +own kernel sources. The remainder of this manual provides instructions for completing specific Linux kernel development tasks. These instructions assume you -are comfortable working with -`BitBake <http://openembedded.org/wiki/Bitbake>`__ recipes and basic +are comfortable working with :oe_wiki:`BitBake </Bitbake>` recipes and basic open-source development tools. Understanding these concepts will facilitate the process of working with the kernel recipes. If you find you need some additional background, please be sure to review and understand the following documentation: -- :doc:`../brief-yoctoprojectqs/brief-yoctoprojectqs` document. +- :doc:`/brief-yoctoprojectqs/index` document. -- :doc:`../overview-manual/overview-manual`. +- :doc:`/overview-manual/index`. - :ref:`devtool - workflow <sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow>` + workflow <sdk-manual/extensible:using \`\`devtool\`\` in your sdk workflow>` as described in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual. -- The ":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`" +- The ":ref:`dev-manual/layers:understanding and creating layers`" section in the Yocto Project Development Tasks Manual. -- The "`Kernel Modification - Workflow <#kernel-modification-workflow>`__" section. +- The ":ref:`kernel-dev/intro:kernel modification workflow`" section. Kernel Modification Workflow ============================ @@ -110,47 +106,47 @@ modification workflow. The illustration and accompanying list provide general information and references for further information. .. image:: figures/kernel-dev-flow.png - :align: center + :width: 100% -1. *Set up Your Host Development System to Support Development Using the - Yocto Project*: See the ":doc:`../dev-manual/dev-manual-start`" section in +#. *Set up Your Host Development System to Support Development Using the + Yocto Project*: See the ":doc:`/dev-manual/start`" section in the Yocto Project Development Tasks Manual for options on how to get a build host ready to use the Yocto Project. -2. *Set Up Your Host Development System for Kernel Development:* It is - recommended that you use ``devtool`` and an extensible SDK for kernel +#. *Set Up Your Host Development System for Kernel Development:* It is + recommended that you use ``devtool`` for kernel development. Alternatively, you can use traditional kernel development methods with the Yocto Project. Either way, there are steps you need to take to get the development environment ready. - Using ``devtool`` and the eSDK requires that you have a clean build - of the image and that you are set up with the appropriate eSDK. For + Using ``devtool`` requires that you have a clean build + of the image. For more information, see the - ":ref:`kernel-dev/kernel-dev-common:getting ready to develop using \`\`devtool\`\``" + ":ref:`kernel-dev/common:getting ready to develop using \`\`devtool\`\``" section. Using traditional kernel development requires that you have the kernel source available in an isolated local Git repository. For more information, see the - ":ref:`kernel-dev/kernel-dev-common:getting ready for traditional kernel development`" + ":ref:`kernel-dev/common:getting ready for traditional kernel development`" section. -3. *Make Changes to the Kernel Source Code if applicable:* Modifying the +#. *Make Changes to the Kernel Source Code if applicable:* Modifying the kernel does not always mean directly changing source files. However, if you have to do this, you make the changes to the files in the - eSDK's Build Directory if you are using ``devtool``. For more + Yocto's :term:`Build Directory` if you are using ``devtool``. For more information, see the - ":ref:`kernel-dev/kernel-dev-common:using \`\`devtool\`\` to patch the kernel`" + ":ref:`kernel-dev/common:using \`\`devtool\`\` to patch the kernel`" section. If you are using traditional kernel development, you edit the source files in the kernel's local Git repository. For more information, see the - ":ref:`kernel-dev/kernel-dev-common:using traditional kernel development to patch the kernel`" + ":ref:`kernel-dev/common:using traditional kernel development to patch the kernel`" section. -4. *Make Kernel Configuration Changes if Applicable:* If your situation +#. *Make Kernel Configuration Changes if Applicable:* If your situation calls for changing the kernel's configuration, you can use - :ref:`menuconfig <kernel-dev/kernel-dev-common:using \`\`menuconfig\`\`>`, + :ref:`menuconfig <kernel-dev/common:using \`\`menuconfig\`\`>`, which allows you to interactively develop and test the configuration changes you are making to the kernel. Saving changes you make with ``menuconfig`` @@ -158,23 +154,22 @@ general information and references for further information. .. note:: - Try to resist the temptation to directly edit an existing - .config - file, which is found in the Build Directory among the source code + Try to resist the temptation to directly edit an existing ``.config`` + file, which is found in the :term:`Build Directory` among the source code used for the build. Doing so, can produce unexpected results when the OpenEmbedded build system regenerates the configuration file. Once you are satisfied with the configuration changes made using ``menuconfig`` and you have saved them, you can directly compare the resulting ``.config`` file against an existing original and gather - those changes into a `configuration fragment - file <#creating-config-fragments>`__ to be referenced from within the - kernel's ``.bbappend`` file. + those changes into a + :ref:`configuration fragment file <kernel-dev/common:creating configuration fragments>` to be + referenced from within the kernel's ``.bbappend`` file. Additionally, if you are working in a BSP layer and need to modify the BSP's kernel's configuration, you can use ``menuconfig``. -5. *Rebuild the Kernel Image With Your Changes:* Rebuilding the kernel +#. *Rebuild the Kernel Image With Your Changes:* Rebuilding the kernel image applies your changes. Depending on your target hardware, you can verify your changes on actual hardware or perhaps QEMU. diff --git a/documentation/kernel-dev/kernel-dev-advanced.xml b/documentation/kernel-dev/kernel-dev-advanced.xml deleted file mode 100644 index 37177966bf..0000000000 --- a/documentation/kernel-dev/kernel-dev-advanced.xml +++ /dev/null @@ -1,1257 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<chapter id='kernel-dev-advanced'> -<title>Working with Advanced Metadata (<filename>yocto-kernel-cache</filename>)</title> - -<section id='kernel-dev-advanced-overview'> - <title>Overview</title> - - <para> - In addition to supporting configuration fragments and patches, the - Yocto Project kernel tools also support rich - <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink> that you can - use to define complex policies and Board Support Package (BSP) support. - The purpose of the Metadata and the tools that manage it is - to help you manage the complexity of the configuration and sources - used to support multiple BSPs and Linux kernel types. - </para> - - <para> - Kernel Metadata exists in many places. - One area in the Yocto Project - <ulink url='&YOCTO_DOCS_OM_URL;#source-repositories'>Source Repositories</ulink> - is the <filename>yocto-kernel-cache</filename> Git repository. - You can find this repository grouped under the "Yocto Linux Kernel" - heading in the - <ulink url='&YOCTO_GIT_URL;'>Yocto Project Source Repositories</ulink>. - </para> - - <para> - Kernel development tools ("kern-tools") exist also in the Yocto - Project Source Repositories under the "Yocto Linux Kernel" heading - in the <filename>yocto-kernel-tools</filename> Git repository. - The recipe that builds these tools is - <filename>meta/recipes-kernel/kern-tools/kern-tools-native_git.bb</filename> - in the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> - (e.g. <filename>poky</filename>). - </para> -</section> - -<section id='using-kernel-metadata-in-a-recipe'> - <title>Using Kernel Metadata in a Recipe</title> - - <para> - As mentioned in the introduction, the Yocto Project contains kernel - Metadata, which is located in the - <filename>yocto-kernel-cache</filename> Git repository. - This Metadata defines Board Support Packages (BSPs) that - correspond to definitions in linux-yocto recipes for corresponding BSPs. - A BSP consists of an aggregation of kernel policy and enabled - hardware-specific features. - The BSP can be influenced from within the linux-yocto recipe. - <note> - A Linux kernel recipe that contains kernel Metadata (e.g. - inherits from the <filename>linux-yocto.inc</filename> file) - is said to be a "linux-yocto style" recipe. - </note> - </para> - - <para> - Every linux-yocto style recipe must define the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink> - variable. - This variable is typically set to the same value as the - <filename>MACHINE</filename> variable, which is used by - <ulink url='&YOCTO_DOCS_REF_URL;#bitbake-term'>BitBake</ulink>. - However, in some cases, the variable might instead refer to the - underlying platform of the <filename>MACHINE</filename>. - </para> - - <para> - Multiple BSPs can reuse the same <filename>KMACHINE</filename> - name if they are built using the same BSP description. - Multiple Corei7-based BSPs could share the same "intel-corei7-64" - value for <filename>KMACHINE</filename>. - It is important to realize that <filename>KMACHINE</filename> is - just for kernel mapping, while <filename>MACHINE</filename> - is the machine type within a BSP Layer. - Even with this distinction, however, these two variables can hold - the same value. - See the <link linkend='bsp-descriptions'>BSP Descriptions</link> - section for more information. - </para> - - <para> - Every linux-yocto style recipe must also indicate the Linux kernel - source repository branch used to build the Linux kernel. - The <ulink url='&YOCTO_DOCS_REF_URL;#var-KBRANCH'><filename>KBRANCH</filename></ulink> - variable must be set to indicate the branch. - <note> - You can use the <filename>KBRANCH</filename> value to define an - alternate branch typically with a machine override as shown here - from the <filename>meta-yocto-bsp</filename> layer: - <literallayout class='monospaced'> - KBRANCH_edgerouter = "standard/edgerouter" - </literallayout> - </note> - </para> - - <para> - The linux-yocto style recipes can optionally define the following - variables: - <literallayout class='monospaced'> - KERNEL_FEATURES - LINUX_KERNEL_TYPE - </literallayout> - </para> - - <para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink> - defines the kernel type to be - used in assembling the configuration. - If you do not specify a <filename>LINUX_KERNEL_TYPE</filename>, - it defaults to "standard". - Together with <filename>KMACHINE</filename>, - <filename>LINUX_KERNEL_TYPE</filename> defines the search - arguments used by the kernel tools to find the - appropriate description within the kernel Metadata with which to - build out the sources and configuration. - The linux-yocto recipes define "standard", "tiny", and "preempt-rt" - kernel types. - See the "<link linkend='kernel-types'>Kernel Types</link>" section - for more information on kernel types. - </para> - - <para> - During the build, the kern-tools search for the BSP description - file that most closely matches the <filename>KMACHINE</filename> - and <filename>LINUX_KERNEL_TYPE</filename> variables passed in from the - recipe. - The tools use the first BSP description it finds that match - both variables. - If the tools cannot find a match, they issue a warning. - </para> - - <para> - The tools first search for the <filename>KMACHINE</filename> and - then for the <filename>LINUX_KERNEL_TYPE</filename>. - If the tools cannot find a partial match, they will use the - sources from the <filename>KBRANCH</filename> and any configuration - specified in the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>. - </para> - - <para> - You can use the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink> - variable - to include features (configuration fragments, patches, or both) that - are not already included by the <filename>KMACHINE</filename> and - <filename>LINUX_KERNEL_TYPE</filename> variable combination. - For example, to include a feature specified as - "features/netfilter/netfilter.scc", - specify: - <literallayout class='monospaced'> - KERNEL_FEATURES += "features/netfilter/netfilter.scc" - </literallayout> - To include a feature called "cfg/sound.scc" just for the - <filename>qemux86</filename> machine, specify: - <literallayout class='monospaced'> - KERNEL_FEATURES_append_qemux86 = " cfg/sound.scc" - </literallayout> - The value of the entries in <filename>KERNEL_FEATURES</filename> - are dependent on their location within the kernel Metadata itself. - The examples here are taken from the - <filename>yocto-kernel-cache</filename> repository. - Each branch of this repository contains "features" and "cfg" - subdirectories at the top-level. - For more information, see the - "<link linkend='kernel-metadata-syntax'>Kernel Metadata Syntax</link>" - section. - </para> -</section> - -<section id='kernel-metadata-syntax'> - <title>Kernel Metadata Syntax</title> - - <para> - The kernel Metadata consists of three primary types of files: - <filename>scc</filename> - <footnote> - <para> - <filename>scc</filename> stands for Series Configuration - Control, but the naming has less significance in the - current implementation of the tooling than it had in the - past. - Consider <filename>scc</filename> files to be description files. - </para> - </footnote> - description files, configuration fragments, and patches. - The <filename>scc</filename> files define variables and include or - otherwise reference any of the three file types. - The description files are used to aggregate all types of kernel - Metadata into - what ultimately describes the sources and the configuration required - to build a Linux kernel tailored to a specific machine. - </para> - - <para> - The <filename>scc</filename> description files are used to define two - fundamental types of kernel Metadata: - <itemizedlist> - <listitem><para>Features</para></listitem> - <listitem><para>Board Support Packages (BSPs)</para></listitem> - </itemizedlist> - </para> - - <para> - Features aggregate sources in the form of patches and configuration - fragments into a modular reusable unit. - You can use features to implement conceptually separate kernel - Metadata descriptions such as pure configuration fragments, - simple patches, complex features, and kernel types. - <link linkend='kernel-types'>Kernel types</link> define general - kernel features and policy to be reused in the BSPs. - </para> - - <para> - BSPs define hardware-specific features and aggregate them with kernel - types to form the final description of what will be assembled and built. - </para> - - <para> - While the kernel Metadata syntax does not enforce any logical - separation of configuration fragments, patches, features or kernel - types, best practices dictate a logical separation of these types - of Metadata. - The following Metadata file hierarchy is recommended: - <literallayout class='monospaced'> - <replaceable>base</replaceable>/ - bsp/ - cfg/ - features/ - ktypes/ - patches/ - </literallayout> - </para> - - <para> - The <filename>bsp</filename> directory contains the - <link linkend='bsp-descriptions'>BSP descriptions</link>. - The remaining directories all contain "features". - Separating <filename>bsp</filename> from the rest of the structure - aids conceptualizing intended usage. - </para> - - <para> - Use these guidelines to help place your <filename>scc</filename> - description files within the structure: - <itemizedlist> - <listitem><para>If your file contains - only configuration fragments, place the file in the - <filename>cfg</filename> directory.</para></listitem> - <listitem><para>If your file contains - only source-code fixes, place the file in the - <filename>patches</filename> directory.</para></listitem> - <listitem><para>If your file encapsulates - a major feature, often combining sources and configurations, - place the file in <filename>features</filename> directory. - </para></listitem> - <listitem><para>If your file aggregates - non-hardware configuration and patches in order to define a - base kernel policy or major kernel type to be reused across - multiple BSPs, place the file in <filename>ktypes</filename> - directory. - </para></listitem> - </itemizedlist> - </para> - - <para> - These distinctions can easily become blurred - especially as - out-of-tree features slowly merge upstream over time. - Also, remember that how the description files are placed is - a purely logical organization and has no impact on the functionality - of the kernel Metadata. - There is no impact because all of <filename>cfg</filename>, - <filename>features</filename>, <filename>patches</filename>, and - <filename>ktypes</filename>, contain "features" as far as the kernel - tools are concerned. - </para> - - <para> - Paths used in kernel Metadata files are relative to - <replaceable>base</replaceable>, which is either - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - if you are creating Metadata in - <link linkend='recipe-space-metadata'>recipe-space</link>, - or the top level of - <ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache/tree/'><filename>yocto-kernel-cache</filename></ulink> - if you are creating - <link linkend='metadata-outside-the-recipe-space'>Metadata outside of the recipe-space</link>. - </para> - - <section id='configuration'> - <title>Configuration</title> - - <para> - The simplest unit of kernel Metadata is the configuration-only - feature. - This feature consists of one or more Linux kernel configuration - parameters in a configuration fragment file - (<filename>.cfg</filename>) and a <filename>.scc</filename> file - that describes the fragment. - </para> - - <para> - As an example, consider the Symmetric Multi-Processing (SMP) - fragment used with the <filename>linux-yocto-4.12</filename> - kernel as defined outside of the recipe space (i.e. - <filename>yocto-kernel-cache</filename>). - This Metadata consists of two files: <filename>smp.scc</filename> - and <filename>smp.cfg</filename>. - You can find these files in the <filename>cfg</filename> directory - of the <filename>yocto-4.12</filename> branch in the - <filename>yocto-kernel-cache</filename> Git repository: - <literallayout class='monospaced'> - cfg/smp.scc: - define KFEATURE_DESCRIPTION "Enable SMP for 32 bit builds" - define KFEATURE_COMPATIBILITY all - - kconf hardware smp.cfg - - cfg/smp.cfg: - CONFIG_SMP=y - CONFIG_SCHED_SMT=y - # Increase default NR_CPUS from 8 to 64 so that platform with - # more than 8 processors can be all activated at boot time - CONFIG_NR_CPUS=64 - # The following is needed when setting NR_CPUS to something - # greater than 8 on x86 architectures, it should be automatically - # disregarded by Kconfig when using a different arch - CONFIG_X86_BIGSMP=y - </literallayout> - You can find general information on configuration fragment files in - the - "<link linkend='creating-config-fragments'>Creating Configuration Fragments</link>" - section. - </para> - - <para> - Within the <filename>smp.scc</filename> file, the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KFEATURE_DESCRIPTION'><filename>KFEATURE_DESCRIPTION</filename></ulink> - statement provides a short description of the fragment. - Higher level kernel tools use this description. - </para> - - <para> - Also within the <filename>smp.scc</filename> file, the - <filename>kconf</filename> command includes the - actual configuration fragment in an <filename>.scc</filename> - file, and the "hardware" keyword identifies the fragment as - being hardware enabling, as opposed to general policy, - which would use the "non-hardware" keyword. - The distinction is made for the benefit of the configuration - validation tools, which warn you if a hardware fragment - overrides a policy set by a non-hardware fragment. - <note> - The description file can include multiple - <filename>kconf</filename> statements, one per fragment. - </note> - </para> - - <para> - As described in the - "<link linkend='validating-configuration'>Validating Configuration</link>" - section, you can use the following BitBake command to audit your - configuration: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c kernel_configcheck -f - </literallayout> - </para> - </section> - - <section id='patches'> - <title>Patches</title> - - <para> - Patch descriptions are very similar to configuration fragment - descriptions, which are described in the previous section. - However, instead of a <filename>.cfg</filename> file, these - descriptions work with source patches (i.e. - <filename>.patch</filename> files). - </para> - - <para> - A typical patch includes a description file and the patch itself. - As an example, consider the build patches used with the - <filename>linux-yocto-4.12</filename> kernel as defined outside of - the recipe space (i.e. <filename>yocto-kernel-cache</filename>). - This Metadata consists of several files: - <filename>build.scc</filename> and a set of - <filename>*.patch</filename> files. - You can find these files in the <filename>patches/build</filename> - directory of the <filename>yocto-4.12</filename> branch in the - <filename>yocto-kernel-cache</filename> Git repository. - </para> - - <para> - The following listings show the <filename>build.scc</filename> - file and part of the - <filename>modpost-mask-trivial-warnings.patch</filename> file: - <literallayout class='monospaced'> - patches/build/build.scc: - patch arm-serialize-build-targets.patch - patch powerpc-serialize-image-targets.patch - patch kbuild-exclude-meta-directory-from-distclean-processi.patch - - # applied by kgit - # patch kbuild-add-meta-files-to-the-ignore-li.patch - - patch modpost-mask-trivial-warnings.patch - patch menuconfig-check-lxdiaglog.sh-Allow-specification-of.patch - - patches/build/modpost-mask-trivial-warnings.patch: - From bd48931bc142bdd104668f3a062a1f22600aae61 Mon Sep 17 00:00:00 2001 - From: Paul Gortmaker <paul.gortmaker@windriver.com> - Date: Sun, 25 Jan 2009 17:58:09 -0500 - Subject: [PATCH] modpost: mask trivial warnings - - Newer HOSTCC will complain about various stdio fcns because - . - . - . - char *dump_write = NULL, *files_source = NULL; - int opt; - -- - 2.10.1 - - generated by cgit v0.10.2 at 2017-09-28 15:23:23 (GMT) - </literallayout> - The description file can include multiple patch statements where - each statement handles a single patch. - In the example <filename>build.scc</filename> file, five patch - statements exist for the five patches in the directory. - </para> - - <para> - You can create a typical <filename>.patch</filename> file using - <filename>diff -Nurp</filename> or - <filename>git format-patch</filename> commands. - For information on how to create patches, see the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - and - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - sections. - </para> - </section> - - <section id='features'> - <title>Features</title> - - <para> - Features are complex kernel Metadata types that consist - of configuration fragments, patches, and possibly other feature - description files. - As an example, consider the following generic listing: - <literallayout class='monospaced'> - features/<replaceable>myfeature</replaceable>.scc - define KFEATURE_DESCRIPTION "Enable <replaceable>myfeature</replaceable>" - - patch 0001-<replaceable>myfeature</replaceable>-core.patch - patch 0002-<replaceable>myfeature</replaceable>-interface.patch - - include cfg/<replaceable>myfeature</replaceable>_dependency.scc - kconf non-hardware <replaceable>myfeature</replaceable>.cfg - </literallayout> - This example shows how the <filename>patch</filename> and - <filename>kconf</filename> commands are used as well as - how an additional feature description file is included with - the <filename>include</filename> command. - </para> - - <para> - Typically, features are less granular than configuration - fragments and are more likely than configuration fragments - and patches to be the types of things you want to specify - in the <filename>KERNEL_FEATURES</filename> variable of the - Linux kernel recipe. - See the "<link linkend='using-kernel-metadata-in-a-recipe'>Using Kernel Metadata in a Recipe</link>" - section earlier in the manual. - </para> - </section> - - <section id='kernel-types'> - <title>Kernel Types</title> - - <para> - A kernel type defines a high-level kernel policy by - aggregating non-hardware configuration fragments with - patches you want to use when building a Linux kernel of a - specific type (e.g. a real-time kernel). - Syntactically, kernel types are no different than features - as described in the "<link linkend='features'>Features</link>" - section. - The - <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink> - variable in the kernel recipe selects the kernel type. - For example, in the <filename>linux-yocto_4.12.bb</filename> - kernel recipe found in - <filename>poky/meta/recipes-kernel/linux</filename>, a - <ulink url='&YOCTO_DOCS_BB_URL;#require-inclusion'><filename>require</filename></ulink> - directive includes the - <filename>poky/meta/recipes-kernel/linux/linux-yocto.inc</filename> - file, which has the following statement that defines the default - kernel type: - <literallayout class='monospaced'> - LINUX_KERNEL_TYPE ??= "standard" - </literallayout> - </para> - - <para> - Another example would be the real-time kernel (i.e. - <filename>linux-yocto-rt_4.12.bb</filename>). - This kernel recipe directly sets the kernel type as follows: - <literallayout class='monospaced'> - LINUX_KERNEL_TYPE = "preempt-rt" - </literallayout> - <note> - You can find kernel recipes in the - <filename>meta/recipes-kernel/linux</filename> directory of the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> - (e.g. <filename>poky/meta/recipes-kernel/linux/linux-yocto_4.12.bb</filename>). - See the "<link linkend='using-kernel-metadata-in-a-recipe'>Using Kernel Metadata in a Recipe</link>" - section for more information. - </note> - </para> - - <para> - Three kernel types ("standard", "tiny", and "preempt-rt") are - supported for Linux Yocto kernels: - <itemizedlist> - <listitem><para>"standard": - Includes the generic Linux kernel policy of the Yocto - Project linux-yocto kernel recipes. - This policy includes, among other things, which file - systems, networking options, core kernel features, and - debugging and tracing options are supported. - </para></listitem> - <listitem><para>"preempt-rt": - Applies the <filename>PREEMPT_RT</filename> - patches and the configuration options required to - build a real-time Linux kernel. - This kernel type inherits from the "standard" kernel type. - </para></listitem> - <listitem><para>"tiny": - Defines a bare minimum configuration meant to serve as a - base for very small Linux kernels. - The "tiny" kernel type is independent from the "standard" - configuration. - Although the "tiny" kernel type does not currently include - any source changes, it might in the future. - </para></listitem> - </itemizedlist> - </para> - - <para> - For any given kernel type, the Metadata is defined by the - <filename>.scc</filename> (e.g. <filename>standard.scc</filename>). - Here is a partial listing for the <filename>standard.scc</filename> - file, which is found in the <filename>ktypes/standard</filename> - directory of the <filename>yocto-kernel-cache</filename> Git - repository: - <literallayout class='monospaced'> - # Include this kernel type fragment to get the standard features and - # configuration values. - - # Note: if only the features are desired, but not the configuration - # then this should be included as: - # include ktypes/standard/standard.scc nocfg - # if no chained configuration is desired, include it as: - # include ktypes/standard/standard.scc nocfg inherit - - - - include ktypes/base/base.scc - branch standard - - kconf non-hardware standard.cfg - - include features/kgdb/kgdb.scc - . - . - . - - include cfg/net/ip6_nf.scc - include cfg/net/bridge.scc - - include cfg/systemd.scc - - include features/rfkill/rfkill.scc - </literallayout> - </para> - - <para> - As with any <filename>.scc</filename> file, a - kernel type definition can aggregate other - <filename>.scc</filename> files with - <filename>include</filename> commands. - These definitions can also directly pull in - configuration fragments and patches with the - <filename>kconf</filename> and <filename>patch</filename> - commands, respectively. - </para> - - <note> - It is not strictly necessary to create a kernel type - <filename>.scc</filename> file. - The Board Support Package (BSP) file can implicitly define - the kernel type using a <filename>define - <ulink url='&YOCTO_DOCS_REF_URL;#var-KTYPE'>KTYPE</ulink> myktype</filename> - line. - See the "<link linkend='bsp-descriptions'>BSP Descriptions</link>" - section for more information. - </note> - </section> - - <section id='bsp-descriptions'> - <title>BSP Descriptions</title> - - <para> - BSP descriptions (i.e. <filename>*.scc</filename> files) - combine kernel types with hardware-specific features. - The hardware-specific Metadata is typically defined - independently in the BSP layer, and then aggregated with each - supported kernel type. - <note> - For BSPs supported by the Yocto Project, the BSP description - files are located in the <filename>bsp</filename> directory - of the - <ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache/tree/bsp'><filename>yocto-kernel-cache</filename></ulink> - repository organized under the "Yocto Linux Kernel" heading - in the - <ulink url='http://git.yoctoproject.org/cgit/cgit.cgi'>Yocto Project Source Repositories</ulink>. - </note> - </para> - - <para> - This section overviews the BSP description structure, the - aggregation concepts, and presents a detailed example using - a BSP supported by the Yocto Project (i.e. BeagleBone Board). - For complete information on BSP layer file hierarchy, see the - <ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>. - </para> - - <section id='bsp-description-file-overview'> - <title>Overview</title> - - <para> - For simplicity, consider the following root BSP layer - description files for the BeagleBone board. - These files employ both a structure and naming convention - for consistency. - The naming convention for the file is as follows: - <literallayout class='monospaced'> - <replaceable>bsp_root_name</replaceable>-<replaceable>kernel_type</replaceable>.scc - </literallayout> - Here are some example root layer BSP filenames for the - BeagleBone Board BSP, which is supported by the Yocto Project: - <literallayout class='monospaced'> - beaglebone-standard.scc - beaglebone-preempt-rt.scc - </literallayout> - Each file uses the root name (i.e "beaglebone") BSP name - followed by the kernel type. - </para> - - <para> - Examine the <filename>beaglebone-standard.scc</filename> - file: - <literallayout class='monospaced'> - define KMACHINE beaglebone - define KTYPE standard - define KARCH arm - - include ktypes/standard/standard.scc - branch beaglebone - - include beaglebone.scc - - # default policy for standard kernels - include features/latencytop/latencytop.scc - include features/profiling/profiling.scc - </literallayout> - Every top-level BSP description file should define the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink>, - <ulink url='&YOCTO_DOCS_REF_URL;#var-KTYPE'><filename>KTYPE</filename></ulink>, - and <ulink url='&YOCTO_DOCS_REF_URL;#var-KARCH'><filename>KARCH</filename></ulink> - variables. - These variables allow the OpenEmbedded build system to identify - the description as meeting the criteria set by the recipe being - built. - This example supports the "beaglebone" machine for the - "standard" kernel and the "arm" architecture. - </para> - - <para> - Be aware that a hard link between the - <filename>KTYPE</filename> variable and a kernel type - description file does not exist. - Thus, if you do not have the kernel type defined in your kernel - Metadata as it is here, you only need to ensure that the - <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_KERNEL_TYPE'><filename>LINUX_KERNEL_TYPE</filename></ulink> - variable in the kernel recipe and the - <filename>KTYPE</filename> variable in the BSP description - file match. - </para> - - <para> - To separate your kernel policy from your hardware configuration, - you include a kernel type (<filename>ktype</filename>), such as - "standard". - In the previous example, this is done using the following: - <literallayout class='monospaced'> - include ktypes/standard/standard.scc - </literallayout> - This file aggregates all the configuration fragments, patches, - and features that make up your standard kernel policy. - See the "<link linkend='kernel-types'>Kernel Types</link>" - section for more information. - </para> - - <para> - To aggregate common configurations and features specific to the - kernel for <replaceable>mybsp</replaceable>, use the following: - <literallayout class='monospaced'> - include <replaceable>mybsp</replaceable>.scc - </literallayout> - You can see that in the BeagleBone example with the following: - <literallayout class='monospaced'> - include beaglebone.scc - </literallayout> - For information on how to break a complete - <filename>.config</filename> file into the various - configuration fragments, see the - "<link linkend='creating-config-fragments'>Creating Configuration Fragments</link>" - section. - </para> - - <para> - Finally, if you have any configurations specific to the - hardware that are not in a <filename>*.scc</filename> file, - you can include them as follows: - <literallayout class='monospaced'> - kconf hardware <replaceable>mybsp</replaceable>-<replaceable>extra</replaceable>.cfg - </literallayout> - The BeagleBone example does not include these types of - configurations. - However, the Malta 32-bit board does ("mti-malta32"). - Here is the <filename>mti-malta32-le-standard.scc</filename> - file: - <literallayout class='monospaced'> - define KMACHINE mti-malta32-le - define KMACHINE qemumipsel - define KTYPE standard - define KARCH mips - - include ktypes/standard/standard.scc - branch mti-malta32 - - include mti-malta32.scc - kconf hardware mti-malta32-le.cfg - </literallayout> - </para> - </section> - - <section id='bsp-description-file-example-minnow'> - <title>Example</title> - - <para> - Many real-world examples are more complex. - Like any other <filename>.scc</filename> file, BSP - descriptions can aggregate features. - Consider the Minnow BSP definition given the - <filename>linux-yocto-4.4</filename> branch of the - <filename>yocto-kernel-cache</filename> (i.e. - <filename>yocto-kernel-cache/bsp/minnow/minnow.scc</filename>): - <note> - Although the Minnow Board BSP is unused, the Metadata - remains and is being used here just as an example. - </note> - <literallayout class='monospaced'> - include cfg/x86.scc - include features/eg20t/eg20t.scc - include cfg/dmaengine.scc - include features/power/intel.scc - include cfg/efi.scc - include features/usb/ehci-hcd.scc - include features/usb/ohci-hcd.scc - include features/usb/usb-gadgets.scc - include features/usb/touchscreen-composite.scc - include cfg/timer/hpet.scc - include features/leds/leds.scc - include features/spi/spidev.scc - include features/i2c/i2cdev.scc - include features/mei/mei-txe.scc - - # Earlyprintk and port debug requires 8250 - kconf hardware cfg/8250.cfg - - kconf hardware minnow.cfg - kconf hardware minnow-dev.cfg - </literallayout> - </para> - - <para> - The <filename>minnow.scc</filename> description file includes - a hardware configuration fragment - (<filename>minnow.cfg</filename>) specific to the Minnow - BSP as well as several more general configuration - fragments and features enabling hardware found on the - machine. - This <filename>minnow.scc</filename> description file is then - included in each of the three - "minnow" description files for the supported kernel types - (i.e. "standard", "preempt-rt", and "tiny"). - Consider the "minnow" description for the "standard" kernel - type (i.e. <filename>minnow-standard.scc</filename>: - <literallayout class='monospaced'> - define KMACHINE minnow - define KTYPE standard - define KARCH i386 - - include ktypes/standard - - include minnow.scc - - # Extra minnow configs above the minimal defined in minnow.scc - include cfg/efi-ext.scc - include features/media/media-all.scc - include features/sound/snd_hda_intel.scc - - # The following should really be in standard.scc - # USB live-image support - include cfg/usb-mass-storage.scc - include cfg/boot-live.scc - - # Basic profiling - include features/latencytop/latencytop.scc - include features/profiling/profiling.scc - - # Requested drivers that don't have an existing scc - kconf hardware minnow-drivers-extra.cfg - </literallayout> - The <filename>include</filename> command midway through the file - includes the <filename>minnow.scc</filename> description that - defines all enabled hardware for the BSP that is common to - all kernel types. - Using this command significantly reduces duplication. - </para> - - <para> - Now consider the "minnow" description for the "tiny" kernel - type (i.e. <filename>minnow-tiny.scc</filename>): - <literallayout class='monospaced'> - define KMACHINE minnow - define KTYPE tiny - define KARCH i386 - - include ktypes/tiny - - include minnow.scc - </literallayout> - As you might expect, the "tiny" description includes quite a - bit less. - In fact, it includes only the minimal policy defined by the - "tiny" kernel type and the hardware-specific configuration - required for booting the machine along with the most basic - functionality of the system as defined in the base "minnow" - description file. - </para> - - <para> - Notice again the three critical variables: - <ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink>, - <ulink url='&YOCTO_DOCS_REF_URL;#var-KTYPE'><filename>KTYPE</filename></ulink>, - and - <ulink url='&YOCTO_DOCS_REF_URL;#var-KARCH'><filename>KARCH</filename></ulink>. - Of these variables, only <filename>KTYPE</filename> - has changed to specify the "tiny" kernel type. - </para> - </section> - </section> -</section> - -<section id='kernel-metadata-location'> - <title>Kernel Metadata Location</title> - - <para> - Kernel Metadata always exists outside of the kernel tree either - defined in a kernel recipe (recipe-space) or outside of the recipe. - Where you choose to define the Metadata depends on what you want - to do and how you intend to work. - Regardless of where you define the kernel Metadata, the syntax used - applies equally. - </para> - - <para> - If you are unfamiliar with the Linux kernel and only wish - to apply a configuration and possibly a couple of patches provided to - you by others, the recipe-space method is recommended. - This method is also a good approach if you are working with Linux kernel - sources you do not control or if you just do not want to maintain a - Linux kernel Git repository on your own. - For partial information on how you can define kernel Metadata in - the recipe-space, see the - "<link linkend='modifying-an-existing-recipe'>Modifying an Existing Recipe</link>" - section. - </para> - - <para> - Conversely, if you are actively developing a kernel and are already - maintaining a Linux kernel Git repository of your own, you might find - it more convenient to work with kernel Metadata kept outside the - recipe-space. - Working with Metadata in this area can make iterative development of - the Linux kernel more efficient outside of the BitBake environment. - </para> - - <section id='recipe-space-metadata'> - <title>Recipe-Space Metadata</title> - - <para> - When stored in recipe-space, the kernel Metadata files reside in a - directory hierarchy below - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>. - For a linux-yocto recipe or for a Linux kernel recipe derived - by copying and modifying - <filename>oe-core/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb</filename> - to a recipe in your layer, <filename>FILESEXTRAPATHS</filename> - is typically set to - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-THISDIR'><filename>THISDIR</filename></ulink><filename>}/${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename>. - See the "<link linkend='modifying-an-existing-recipe'>Modifying an Existing Recipe</link>" - section for more information. - </para> - - <para> - Here is an example that shows a trivial tree of kernel Metadata - stored in recipe-space within a BSP layer: - <literallayout class='monospaced'> - meta-<replaceable>my_bsp_layer</replaceable>/ - `-- recipes-kernel - `-- linux - `-- linux-yocto - |-- bsp-standard.scc - |-- bsp.cfg - `-- standard.cfg - </literallayout> - </para> - - <para> - When the Metadata is stored in recipe-space, you must take - steps to ensure BitBake has the necessary information to decide - what files to fetch and when they need to be fetched again. - It is only necessary to specify the <filename>.scc</filename> - files on the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>. - BitBake parses them and fetches any files referenced in the - <filename>.scc</filename> files by the <filename>include</filename>, - <filename>patch</filename>, or <filename>kconf</filename> commands. - Because of this, it is necessary to bump the recipe - <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink> - value when changing the content of files not explicitly listed - in the <filename>SRC_URI</filename>. - </para> - - <para> - If the BSP description is in recipe space, you cannot simply list - the <filename>*.scc</filename> in the <filename>SRC_URI</filename> - statement. - You need to use the following form from your kernel append file: - <literallayout class='monospaced'> - SRC_URI_append_<replaceable>myplatform</replaceable> = " \ - file://<replaceable>myplatform</replaceable>;type=kmeta;destsuffix=<replaceable>myplatform</replaceable> \ - " - </literallayout> - </para> - </section> - - <section id='metadata-outside-the-recipe-space'> - <title>Metadata Outside the Recipe-Space</title> - - <para> - When stored outside of the recipe-space, the kernel Metadata - files reside in a separate repository. - The OpenEmbedded build system adds the Metadata to the build as - a "type=kmeta" repository through the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - variable. - As an example, consider the following <filename>SRC_URI</filename> - statement from the <filename>linux-yocto_4.12.bb</filename> - kernel recipe: - <literallayout class='monospaced'> - SRC_URI = "git://git.yoctoproject.org/linux-yocto-4.12.git;name=machine;branch=${KBRANCH}; \ - git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-4.12;destsuffix=${KMETA}" - </literallayout> - <filename>${KMETA}</filename>, in this context, is simply used to - name the directory into which the Git fetcher places the Metadata. - This behavior is no different than any multi-repository - <filename>SRC_URI</filename> statement used in a recipe (e.g. - see the previous section). - </para> - - <para> - You can keep kernel Metadata in a "kernel-cache", which is a - directory containing configuration fragments. - As with any Metadata kept outside the recipe-space, you simply - need to use the <filename>SRC_URI</filename> statement with the - "type=kmeta" attribute. - Doing so makes the kernel Metadata available during the - configuration phase. - </para> - - <para> - If you modify the Metadata, you must not forget to update the - <filename>SRCREV</filename> statements in the kernel's recipe. - In particular, you need to update the - <filename>SRCREV_meta</filename> variable to match the commit in - the <filename>KMETA</filename> branch you wish to use. - Changing the data in these branches and not updating the - <filename>SRCREV</filename> statements to match will cause the - build to fetch an older commit. - </para> - </section> -</section> - -<section id='organizing-your-source'> - <title>Organizing Your Source</title> - - <para> - Many recipes based on the <filename>linux-yocto-custom.bb</filename> - recipe use Linux kernel sources that have only a single - branch - "master". - This type of repository structure is fine for linear development - supporting a single machine and architecture. - However, if you work with multiple boards and architectures, - a kernel source repository with multiple branches is more - efficient. - For example, suppose you need a series of patches for one board to boot. - Sometimes, these patches are works-in-progress or fundamentally wrong, - yet they are still necessary for specific boards. - In these situations, you most likely do not want to include these - patches in every kernel you build (i.e. have the patches as part of - the lone "master" branch). - It is situations like these that give rise to multiple branches used - within a Linux kernel sources Git repository. - </para> - - <para> - Repository organization strategies exist that maximize source reuse, - remove redundancy, and logically order your changes. - This section presents strategies for the following cases: - <itemizedlist> - <listitem><para>Encapsulating patches in a feature description - and only including the patches in the BSP descriptions of - the applicable boards.</para></listitem> - <listitem><para>Creating a machine branch in your - kernel source repository and applying the patches on that - branch only.</para></listitem> - <listitem><para>Creating a feature branch in your - kernel source repository and merging that branch into your - BSP when needed.</para></listitem> - </itemizedlist> - </para> - - <para> - The approach you take is entirely up to you - and depends on what works best for your development model. - </para> - - <section id='encapsulating-patches'> - <title>Encapsulating Patches</title> - - <para> - if you are reusing patches from an external tree and are not - working on the patches, you might find the encapsulated feature - to be appropriate. - Given this scenario, you do not need to create any branches in the - source repository. - Rather, you just take the static patches you need and encapsulate - them within a feature description. - Once you have the feature description, you simply include that into - the BSP description as described in the - "<link linkend='bsp-descriptions'>BSP Descriptions</link>" - section. - </para> - - <para> - You can find information on how to create patches and BSP - descriptions in the "<link linkend='patches'>Patches</link>" and - "<link linkend='bsp-descriptions'>BSP Descriptions</link>" - sections. - </para> - </section> - - <section id='machine-branches'> - <title>Machine Branches</title> - - <para> - When you have multiple machines and architectures to support, - or you are actively working on board support, it is more - efficient to create branches in the repository based on - individual machines. - Having machine branches allows common source to remain in the - "master" branch with any features specific to a machine stored - in the appropriate machine branch. - This organization method frees you from continually reintegrating - your patches into a feature. - </para> - - <para> - Once you have a new branch, you can set up your kernel Metadata - to use the branch a couple different ways. - In the recipe, you can specify the new branch as the - <filename>KBRANCH</filename> to use for the board as - follows: - <literallayout class='monospaced'> - KBRANCH = "mynewbranch" - </literallayout> - Another method is to use the <filename>branch</filename> command - in the BSP description: - <literallayout class='monospaced'> - mybsp.scc: - define KMACHINE mybsp - define KTYPE standard - define KARCH i386 - include standard.scc - - branch mynewbranch - - include mybsp-hw.scc - </literallayout> - </para> - - <para> - If you find yourself with numerous branches, you might consider - using a hierarchical branching system similar to what the - Yocto Linux Kernel Git repositories use: - <literallayout class='monospaced'> - <replaceable>common</replaceable>/<replaceable>kernel_type</replaceable>/<replaceable>machine</replaceable> - </literallayout> - </para> - - <para> - If you had two kernel types, "standard" and "small" for - instance, three machines, and <replaceable>common</replaceable> - as <filename>mydir</filename>, the branches in your - Git repository might look like this: - <literallayout class='monospaced'> - mydir/base - mydir/standard/base - mydir/standard/machine_a - mydir/standard/machine_b - mydir/standard/machine_c - mydir/small/base - mydir/small/machine_a - </literallayout> - </para> - - <para> - This organization can help clarify the branch relationships. - In this case, <filename>mydir/standard/machine_a</filename> - includes everything in <filename>mydir/base</filename> and - <filename>mydir/standard/base</filename>. - The "standard" and "small" branches add sources specific to those - kernel types that for whatever reason are not appropriate for the - other branches. - <note> - The "base" branches are an artifact of the way Git manages - its data internally on the filesystem: Git will not allow you - to use <filename>mydir/standard</filename> and - <filename>mydir/standard/machine_a</filename> because it - would have to create a file and a directory named "standard". - </note> - </para> - </section> - - <section id='feature-branches'> - <title>Feature Branches</title> - - <para> - When you are actively developing new features, it can be more - efficient to work with that feature as a branch, rather than - as a set of patches that have to be regularly updated. - The Yocto Project Linux kernel tools provide for this with - the <filename>git merge</filename> command. - </para> - - <para> - To merge a feature branch into a BSP, insert the - <filename>git merge</filename> command after any - <filename>branch</filename> commands: - <literallayout class='monospaced'> - mybsp.scc: - define KMACHINE mybsp - define KTYPE standard - define KARCH i386 - include standard.scc - - branch mynewbranch - git merge myfeature - - include mybsp-hw.scc - </literallayout> - </para> - </section> -</section> - -<section id='scc-reference'> - <title>SCC Description File Reference</title> - - <para> - This section provides a brief reference for the commands you can use - within an SCC description file (<filename>.scc</filename>): - <itemizedlist> - <listitem><para> - <filename>branch [ref]</filename>: - Creates a new branch relative to the current branch - (typically <filename>${KTYPE}</filename>) using - the currently checked-out branch, or "ref" if specified. - </para></listitem> - <listitem><para> - <filename>define</filename>: - Defines variables, such as - <ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink>, - <ulink url='&YOCTO_DOCS_REF_URL;#var-KTYPE'><filename>KTYPE</filename></ulink>, - <ulink url='&YOCTO_DOCS_REF_URL;#var-KARCH'><filename>KARCH</filename></ulink>, - and - <ulink url='&YOCTO_DOCS_REF_URL;#var-KFEATURE_DESCRIPTION'><filename>KFEATURE_DESCRIPTION</filename></ulink>. - </para></listitem> - <listitem><para> - <filename>include SCC_FILE</filename>: - Includes an SCC file in the current file. - The file is parsed as if you had inserted it inline. - </para></listitem> - <listitem><para> - <filename>kconf [hardware|non-hardware] CFG_FILE</filename>: - Queues a configuration fragment for merging into the final - Linux <filename>.config</filename> file.</para></listitem> - <listitem><para> - <filename>git merge GIT_BRANCH</filename>: - Merges the feature branch into the current branch. - </para></listitem> - <listitem><para> - <filename>patch PATCH_FILE</filename>: - Applies the patch to the current Git branch. - </para></listitem> - </itemizedlist> - </para> -</section> - -</chapter> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-common.xml b/documentation/kernel-dev/kernel-dev-common.xml deleted file mode 100644 index 8e8a6dbed4..0000000000 --- a/documentation/kernel-dev/kernel-dev-common.xml +++ /dev/null @@ -1,2730 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<chapter id='kernel-dev-common'> -<title>Common Tasks</title> - - <para> - This chapter presents several common tasks you perform when you - work with the Yocto Project Linux kernel. - These tasks include preparing your host development system for - kernel development, preparing a layer, modifying an existing recipe, - patching the kernel, configuring the kernel, iterative development, - working with your own sources, and incorporating out-of-tree modules. - <note> - The examples presented in this chapter work with the Yocto Project - 2.4 Release and forward. - </note> - </para> - - <section id='preparing-the-build-host-to-work-on-the-kernel'> - <title>Preparing the Build Host to Work on the Kernel</title> - - <para> - Before you can do any kernel development, you need to be - sure your build host is set up to use the Yocto Project. - For information on how to get set up, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#dev-preparing-the-build-host'>Preparing the Build Host</ulink>" - section in the Yocto Project Development Tasks Manual. - Part of preparing the system is creating a local Git - repository of the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> - (<filename>poky</filename>) on your system. - Follow the steps in the - "<ulink url='&YOCTO_DOCS_DEV_URL;#cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</ulink>" - section in the Yocto Project Development Tasks Manual to set up your - Source Directory. - <note> - Be sure you check out the appropriate development branch or - you create your local branch by checking out a specific tag - to get the desired version of Yocto Project. - See the - "<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking Out by Branch in Poky</ulink>" - and - "<ulink url='&YOCTO_DOCS_DEV_URL;#checkout-out-by-tag-in-poky'>Checking Out by Tag in Poky</ulink>" - sections in the Yocto Project Development Tasks Manual for more - information. - </note> - </para> - - <para> - Kernel development is best accomplished using - <ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename></ulink> - and not through traditional kernel workflow methods. - The remainder of this section provides information for both - scenarios. - </para> - - <section id='getting-ready-to-develop-using-devtool'> - <title>Getting Ready to Develop Using <filename>devtool</filename></title> - - <para> - Follow these steps to prepare to update the kernel image using - <filename>devtool</filename>. - Completing this procedure leaves you with a clean kernel image - and ready to make modifications as described in the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - section: - <orderedlist> - <listitem><para> - <emphasis>Initialize the BitBake Environment:</emphasis> - Before building an extensible SDK, you need to - initialize the BitBake build environment by sourcing the - build environment script - (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>oe-init-build-env</filename></ulink>): - <literallayout class='monospaced'> - $ cd ~/poky - $ source oe-init-build-env - </literallayout> - <note> - The previous commands assume the - <ulink url='&YOCTO_DOCS_OM_URL;#source-repositories'>Source Repositories</ulink> - (i.e. <filename>poky</filename>) have been cloned - using Git and the local repository is named - "poky". - </note> - </para></listitem> - <listitem><para> - <emphasis>Prepare Your <filename>local.conf</filename> File:</emphasis> - By default, the - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink> - variable is set to "qemux86-64", which is fine if you are - building for the QEMU emulator in 64-bit mode. - However, if you are not, you need to set the - <filename>MACHINE</filename> variable appropriately in - your <filename>conf/local.conf</filename> file found in - the - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink> - (i.e. <filename>~/poky/build</filename> in this - example).</para> - - <para>Also, since you are preparing to work on the - kernel image, you need to set the - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink> - variable to include kernel modules.</para> - - <para>In this example we wish to build for qemux86 so - we must set the <filename>MACHINE</filename> variable - to "qemux86" and also add the "kernel-modules". As described - we do this by appending to <filename>conf/local.conf</filename>: - <literallayout class='monospaced'> - MACHINE = "qemux86" - MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-modules" - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create a Layer for Patches:</emphasis> - You need to create a layer to hold patches created - for the kernel image. - You can use the - <filename>bitbake-layers create-layer</filename> - command as follows: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake-layers create-layer ../../meta-mylayer - NOTE: Starting bitbake server... - Add your new layer with 'bitbake-layers add-layer ../../meta-mylayer' - $ - </literallayout> - <note> - For background information on working with - common and BSP layers, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" - section in the Yocto Project Development Tasks - Manual and the - "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>" - section in the Yocto Project Board Support (BSP) - Developer's Guide, respectively. - For information on how to use the - <filename>bitbake-layers create-layer</filename> - command to quickly set up a layer, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>" - section in the Yocto Project Development Tasks - Manual. - </note> - </para></listitem> - <listitem><para> - <emphasis>Inform the BitBake Build Environment About - Your Layer:</emphasis> - As directed when you created your layer, you need to - add the layer to the - <ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink> - variable in the <filename>bblayers.conf</filename> file - as follows: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake-layers add-layer ../../meta-mylayer - NOTE: Starting bitbake server... - $ - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Build the Extensible SDK:</emphasis> - Use BitBake to build the extensible SDK specifically - for use with images to be run using QEMU: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake core-image-minimal -c populate_sdk_ext - </literallayout> - Once the build finishes, you can find the SDK installer - file (i.e. <filename>*.sh</filename> file) in the - following directory: - <literallayout class='monospaced'> - ~/poky/build/tmp/deploy/sdk - </literallayout> - For this example, the installer file is named - <filename>poky-glibc-x86_64-core-image-minimal-i586-toolchain-ext-&DISTRO;.sh</filename> - </para></listitem> - <listitem><para> - <emphasis>Install the Extensible SDK:</emphasis> - Use the following command to install the SDK. - For this example, install the SDK in the default - <filename>~/poky_sdk</filename> directory: - <literallayout class='monospaced'> - $ cd ~/poky/build/tmp/deploy/sdk - $ ./poky-glibc-x86_64-core-image-minimal-i586-toolchain-ext-&DISTRO;.sh - Poky (Yocto Project Reference Distro) Extensible SDK installer version &DISTRO; - ============================================================================ - Enter target directory for SDK (default: ~/poky_sdk): - You are about to install the SDK to "/home/scottrif/poky_sdk". Proceed [Y/n]? Y - Extracting SDK......................................done - Setting it up... - Extracting buildtools... - Preparing build system... - Parsing recipes: 100% |#################################################################| Time: 0:00:52 - Initializing tasks: 100% |############## ###############################################| Time: 0:00:04 - Checking sstate mirror object availability: 100% |######################################| Time: 0:00:00 - Parsing recipes: 100% |#################################################################| Time: 0:00:33 - Initializing tasks: 100% |##############################################################| Time: 0:00:00 - done - SDK has been successfully set up and is ready to be used. - Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g. - $ . /home/scottrif/poky_sdk/environment-setup-i586-poky-linux - </literallayout> - </para></listitem> - <listitem><para id='setting-up-the-esdk-terminal'> - <emphasis>Set Up a New Terminal to Work With the - Extensible SDK:</emphasis> - You must set up a new terminal to work with the SDK. - You cannot use the same BitBake shell used to build the - installer.</para> - - <para>After opening a new shell, run the SDK environment - setup script as directed by the output from installing - the SDK: - <literallayout class='monospaced'> - $ source ~/poky_sdk/environment-setup-i586-poky-linux - "SDK environment now set up; additionally you may now run devtool to perform development tasks. - Run devtool --help for further details. - </literallayout> - <note> - If you get a warning about attempting to use the - extensible SDK in an environment set up to run - BitBake, you did not use a new shell. - </note> - </para></listitem> - <listitem><para> - <emphasis>Build the Clean Image:</emphasis> - The final step in preparing to work on the kernel is to - build an initial image using - <filename>devtool</filename> in the new terminal you - just set up and initialized for SDK work: - <literallayout class='monospaced'> - $ devtool build-image - Parsing recipes: 100% |##########################################| Time: 0:00:05 - Parsing of 830 .bb files complete (0 cached, 830 parsed). 1299 targets, 47 skipped, 0 masked, 0 errors. - WARNING: No packages to add, building image core-image-minimal unmodified - Loading cache: 100% |############################################| Time: 0:00:00 - Loaded 1299 entries from dependency cache. - NOTE: Resolving any missing task queue dependencies - Initializing tasks: 100% |#######################################| Time: 0:00:07 - Checking sstate mirror object availability: 100% |###############| Time: 0:00:00 - NOTE: Executing SetScene Tasks - NOTE: Executing RunQueue Tasks - NOTE: Tasks Summary: Attempted 2866 tasks of which 2604 didn't need to be rerun and all succeeded. - NOTE: Successfully built core-image-minimal. You can find output files in /home/scottrif/poky_sdk/tmp/deploy/images/qemux86 - </literallayout> - If you were building for actual hardware and not for - emulation, you could flash the image to a USB stick - on <filename>/dev/sdd</filename> and boot your device. - For an example that uses a Minnowboard, see the - <ulink url='https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk'>TipsAndTricks/KernelDevelopmentWithEsdk</ulink> - Wiki page. - </para></listitem> - </orderedlist> - </para> - - <para> - At this point you have set up to start making modifications to - the kernel by using the extensible SDK. - For a continued example, see the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - section. - </para> - </section> - - <section id='getting-ready-for-traditional-kernel-development'> - <title>Getting Ready for Traditional Kernel Development</title> - - <para> - Getting ready for traditional kernel development using the Yocto - Project involves many of the same steps as described in the - previous section. - However, you need to establish a local copy of the kernel source - since you will be editing these files. - </para> - - <para> - Follow these steps to prepare to update the kernel image using - traditional kernel development flow with the Yocto Project. - Completing this procedure leaves you ready to make modifications - to the kernel source as described in the - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - section: - <orderedlist> - <listitem><para> - <emphasis>Initialize the BitBake Environment:</emphasis> - Before you can do anything using BitBake, you need to - initialize the BitBake build environment by sourcing the - build environment script - (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>oe-init-build-env</filename></ulink>). - Also, for this example, be sure that the local branch - you have checked out for <filename>poky</filename> is - the Yocto Project &DISTRO_NAME; branch. - If you need to checkout out the &DISTRO_NAME; branch, - see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking out by Branch in Poky</ulink>" - section in the Yocto Project Development Tasks Manual. - <literallayout class='monospaced'> - $ cd ~/poky - $ git branch - master - * &DISTRO_NAME; - $ source oe-init-build-env - </literallayout> - <note> - The previous commands assume the - <ulink url='&YOCTO_DOCS_OM_URL;#source-repositories'>Source Repositories</ulink> - (i.e. <filename>poky</filename>) have been cloned - using Git and the local repository is named - "poky". - </note> - </para></listitem> - <listitem><para> - <emphasis>Prepare Your <filename>local.conf</filename> - File:</emphasis> - By default, the - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink> - variable is set to "qemux86-64", which is fine if you are - building for the QEMU emulator in 64-bit mode. - However, if you are not, you need to set the - <filename>MACHINE</filename> variable appropriately in - your <filename>conf/local.conf</filename> file found - in the - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink> - (i.e. <filename>~/poky/build</filename> in this - example).</para> - - <para>Also, since you are preparing to work on the - kernel image, you need to set the - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink> - variable to include kernel modules.</para> - - <para>In this example we wish to build for qemux86 so - we must set the <filename>MACHINE</filename> variable - to "qemux86" and also add the "kernel-modules". As described - we do this by appending to <filename>conf/local.conf</filename>: - <literallayout class='monospaced'> - MACHINE = "qemux86" - MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-modules" - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create a Layer for Patches:</emphasis> - You need to create a layer to hold patches created - for the kernel image. - You can use the - <filename>bitbake-layers create-layer</filename> - command as follows: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake-layers create-layer ../../meta-mylayer - NOTE: Starting bitbake server... - Add your new layer with 'bitbake-layers add-layer ../../meta-mylayer' - </literallayout> - <note> - For background information on working with - common and BSP layers, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" - section in the Yocto Project Development Tasks - Manual and the - "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>" - section in the Yocto Project Board Support (BSP) - Developer's Guide, respectively. - For information on how to use the - <filename>bitbake-layers create-layer</filename> - command to quickly set up a layer, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>" - section in the Yocto Project Development Tasks - Manual. - </note> - </para></listitem> - <listitem><para> - <emphasis>Inform the BitBake Build Environment About - Your Layer:</emphasis> - As directed when you created your layer, you need to add - the layer to the - <ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink> - variable in the <filename>bblayers.conf</filename> file - as follows: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake-layers add-layer ../../meta-mylayer - NOTE: Starting bitbake server ... - $ - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create a Local Copy of the Kernel Git - Repository:</emphasis> - You can find Git repositories of supported Yocto Project - kernels organized under "Yocto Linux Kernel" in the - Yocto Project Source Repositories at - <ulink url='&YOCTO_GIT_URL;'></ulink>. - </para> - - <para> - For simplicity, it is recommended that you create your - copy of the kernel Git repository outside of the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>, - which is usually named <filename>poky</filename>. - Also, be sure you are in the - <filename>standard/base</filename> branch. - </para> - - <para> - The following commands show how to create a local copy - of the <filename>linux-yocto-4.12</filename> kernel and - be in the <filename>standard/base</filename> branch. - <note> - The <filename>linux-yocto-4.12</filename> kernel - can be used with the Yocto Project 2.4 release - and forward. - You cannot use the - <filename>linux-yocto-4.12</filename> kernel with - releases prior to Yocto Project 2.4: - </note> - <literallayout class='monospaced'> - $ cd ~ - $ git clone git://git.yoctoproject.org/linux-yocto-4.12 --branch standard/base - Cloning into 'linux-yocto-4.12'... - remote: Counting objects: 6097195, done. - remote: Compressing objects: 100% (901026/901026), done. - remote: Total 6097195 (delta 5152604), reused 6096847 (delta 5152256) - Receiving objects: 100% (6097195/6097195), 1.24 GiB | 7.81 MiB/s, done. - Resolving deltas: 100% (5152604/5152604), done. - Checking connectivity... done. - Checking out files: 100% (59846/59846), done. - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create a Local Copy of the Kernel Cache Git - Repository:</emphasis> - For simplicity, it is recommended that you create your - copy of the kernel cache Git repository outside of the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>, - which is usually named <filename>poky</filename>. - Also, for this example, be sure you are in the - <filename>yocto-4.12</filename> branch. - </para> - - <para> - The following commands show how to create a local copy - of the <filename>yocto-kernel-cache</filename> and - be in the <filename>yocto-4.12</filename> branch: - <literallayout class='monospaced'> - $ cd ~ - $ git clone git://git.yoctoproject.org/yocto-kernel-cache --branch yocto-4.12 - Cloning into 'yocto-kernel-cache'... - remote: Counting objects: 22639, done. - remote: Compressing objects: 100% (9761/9761), done. - remote: Total 22639 (delta 12400), reused 22586 (delta 12347) - Receiving objects: 100% (22639/22639), 22.34 MiB | 6.27 MiB/s, done. - Resolving deltas: 100% (12400/12400), done. - Checking connectivity... done. - </literallayout> - </para></listitem> - </orderedlist> - </para> - - <para> - At this point, you are ready to start making modifications to - the kernel using traditional kernel development steps. - For a continued example, see the - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - section. - </para> - </section> - </section> - - <section id='creating-and-preparing-a-layer'> - <title>Creating and Preparing a Layer</title> - - <para> - If you are going to be modifying kernel recipes, it is recommended - that you create and prepare your own layer in which to do your - work. - Your layer contains its own - <ulink url='&YOCTO_DOCS_REF_URL;#bitbake-term'>BitBake</ulink> - append files (<filename>.bbappend</filename>) and provides a - convenient mechanism to create your own recipe files - (<filename>.bb</filename>) as well as store and use kernel - patch files. - For background information on working with layers, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" - section in the Yocto Project Development Tasks Manual. - <note><title>Tip</title> - The Yocto Project comes with many tools that simplify - tasks you need to perform. - One such tool is the - <filename>bitbake-layers create-layer</filename> - command, which simplifies creating a new layer. - See the - "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>" - section in the Yocto Project Development Tasks Manual for - information on how to use this script to quick set up a - new layer. - </note> - </para> - - <para> - To better understand the layer you create for kernel development, - the following section describes how to create a layer - without the aid of tools. - These steps assume creation of a layer named - <filename>mylayer</filename> in your home directory: - <orderedlist> - <listitem><para> - <emphasis>Create Structure</emphasis>: - Create the layer's structure: - <literallayout class='monospaced'> - $ cd $HOME - $ mkdir meta-mylayer - $ mkdir meta-mylayer/conf - $ mkdir meta-mylayer/recipes-kernel - $ mkdir meta-mylayer/recipes-kernel/linux - $ mkdir meta-mylayer/recipes-kernel/linux/linux-yocto - </literallayout> - The <filename>conf</filename> directory holds your - configuration files, while the - <filename>recipes-kernel</filename> directory holds your - append file and eventual patch files. - </para></listitem> - <listitem><para> - <emphasis>Create the Layer Configuration File</emphasis>: - Move to the <filename>meta-mylayer/conf</filename> - directory and create the <filename>layer.conf</filename> - file as follows: - <literallayout class='monospaced'> - # We have a conf and classes directory, add to BBPATH - BBPATH .= ":${LAYERDIR}" - - # We have recipes-* directories, add to BBFILES - BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \ - ${LAYERDIR}/recipes-*/*/*.bbappend" - - BBFILE_COLLECTIONS += "mylayer" - BBFILE_PATTERN_mylayer = "^${LAYERDIR}/" - BBFILE_PRIORITY_mylayer = "5" - </literallayout> - Notice <filename>mylayer</filename> as part of the last - three statements. - </para></listitem> - <listitem><para> - <emphasis>Create the Kernel Recipe Append File</emphasis>: - Move to the - <filename>meta-mylayer/recipes-kernel/linux</filename> - directory and create the kernel's append file. - This example uses the - <filename>linux-yocto-4.12</filename> kernel. - Thus, the name of the append file is - <filename>linux-yocto_4.12.bbappend</filename>: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - - SRC_URI_append = " file://<replaceable>patch-file-one</replaceable>" - SRC_URI_append = " file://<replaceable>patch-file-two</replaceable>" - SRC_URI_append = " file://<replaceable>patch-file-three</replaceable>" - </literallayout> - The - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - and - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - statements enable the OpenEmbedded build system to find - patch files. - For more information on using append files, see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>" - section in the Yocto Project Development Tasks Manual. - </para></listitem> - </orderedlist> - </para> - </section> - - <section id='modifying-an-existing-recipe'> - <title>Modifying an Existing Recipe</title> - - <para> - In many cases, you can customize an existing linux-yocto recipe to - meet the needs of your project. - Each release of the Yocto Project provides a few Linux - kernel recipes from which you can choose. - These are located in the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> - in <filename>meta/recipes-kernel/linux</filename>. - </para> - - <para> - Modifying an existing recipe can consist of the following: - <itemizedlist> - <listitem><para>Creating the append file</para></listitem> - <listitem><para>Applying patches</para></listitem> - <listitem><para>Changing the configuration</para></listitem> - </itemizedlist> - </para> - - <para> - Before modifying an existing recipe, be sure that you have created - a minimal, custom layer from which you can work. - See the - "<link linkend='creating-and-preparing-a-layer'>Creating and Preparing a Layer</link>" - section for information. - </para> - - <section id='creating-the-append-file'> - <title>Creating the Append File</title> - - <para> - You create this file in your custom layer. - You also name it accordingly based on the linux-yocto recipe - you are using. - For example, if you are modifying the - <filename>meta/recipes-kernel/linux/linux-yocto_4.12.bb</filename> - recipe, the append file will typically be located as follows - within your custom layer: - <literallayout class='monospaced'> - <replaceable>your-layer</replaceable>/recipes-kernel/linux/linux-yocto_4.12.bbappend - </literallayout> - The append file should initially extend the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink> - search path by prepending the directory that contains your - files to the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - variable as follows: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - </literallayout> - The path <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-THISDIR'><filename>THISDIR</filename></ulink><filename>}/${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename> - expands to "linux-yocto" in the current directory for this - example. - If you add any new files that modify the kernel recipe and you - have extended <filename>FILESPATH</filename> as - described above, you must place the files in your layer in the - following area: - <literallayout class='monospaced'> - <replaceable>your-layer</replaceable>/recipes-kernel/linux/linux-yocto/ - </literallayout> - <note>If you are working on a new machine Board Support Package - (BSP), be sure to refer to the - <ulink url='&YOCTO_DOCS_BSP_URL;'>Yocto Project Board Support Package (BSP) Developer's Guide</ulink>. - </note> - </para> - - <para> - As an example, consider the following append file - used by the BSPs in <filename>meta-yocto-bsp</filename>: - <literallayout class='monospaced'> - meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.12.bbappend - </literallayout> - The following listing shows the file. - Be aware that the actual commit ID strings in this - example listing might be different than the actual strings - in the file from the <filename>meta-yocto-bsp</filename> - layer upstream. - <literallayout class='monospaced'> - KBRANCH_genericx86 = "standard/base" - KBRANCH_genericx86-64 = "standard/base" - - KMACHINE_genericx86 ?= "common-pc" - KMACHINE_genericx86-64 ?= "common-pc-64" - KBRANCH_edgerouter = "standard/edgerouter" - KBRANCH_beaglebone = "standard/beaglebone" - - SRCREV_machine_genericx86 ?= "d09f2ce584d60ecb7890550c22a80c48b83c2e19" - SRCREV_machine_genericx86-64 ?= "d09f2ce584d60ecb7890550c22a80c48b83c2e19" - SRCREV_machine_edgerouter ?= "b5c8cfda2dfe296410d51e131289fb09c69e1e7d" - SRCREV_machine_beaglebone ?= "b5c8cfda2dfe296410d51e131289fb09c69e1e7d" - - - COMPATIBLE_MACHINE_genericx86 = "genericx86" - COMPATIBLE_MACHINE_genericx86-64 = "genericx86-64" - COMPATIBLE_MACHINE_edgerouter = "edgerouter" - COMPATIBLE_MACHINE_beaglebone = "beaglebone" - - LINUX_VERSION_genericx86 = "4.12.7" - LINUX_VERSION_genericx86-64 = "4.12.7" - LINUX_VERSION_edgerouter = "4.12.10" - LINUX_VERSION_beaglebone = "4.12.10" - </literallayout> - This append file contains statements used to support - several BSPs that ship with the Yocto Project. - The file defines machines using the - <ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink> - variable and uses the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink> - variable to ensure the machine name used by the OpenEmbedded - build system maps to the machine name used by the Linux Yocto - kernel. - The file also uses the optional - <ulink url='&YOCTO_DOCS_REF_URL;#var-KBRANCH'><filename>KBRANCH</filename></ulink> - variable to ensure the build process uses the - appropriate kernel branch. - </para> - - <para> - Although this particular example does not use it, the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink> - variable could be used to enable features specific to - the kernel. - The append file points to specific commits in the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink> - Git repository and the <filename>meta</filename> Git repository - branches to identify the exact kernel needed to build the - BSP. - </para> - - <para> - One thing missing in this particular BSP, which you will - typically need when developing a BSP, is the kernel - configuration file (<filename>.config</filename>) for your BSP. - When developing a BSP, you probably have a kernel configuration - file or a set of kernel configuration files that, when taken - together, define the kernel configuration for your BSP. - You can accomplish this definition by putting the configurations - in a file or a set of files inside a directory located at the - same level as your kernel's append file and having the same - name as the kernel's main recipe file. - With all these conditions met, simply reference those files in - the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - statement in the append file. - </para> - - <para> - For example, suppose you had some configuration options - in a file called <filename>network_configs.cfg</filename>. - You can place that file inside a directory named - <filename>linux-yocto</filename> and then add - a <filename>SRC_URI</filename> statement such as the - following to the append file. - When the OpenEmbedded build system builds the kernel, the - configuration options are picked up and applied. - <literallayout class='monospaced'> - SRC_URI += "file://network_configs.cfg" - </literallayout> - </para> - - <para> - To group related configurations into multiple files, you - perform a similar procedure. - Here is an example that groups separate configurations - specifically for Ethernet and graphics into their own - files and adds the configurations by using a - <filename>SRC_URI</filename> statement like the following - in your append file: - <literallayout class='monospaced'> - SRC_URI += "file://myconfig.cfg \ - file://eth.cfg \ - file://gfx.cfg" - </literallayout> - </para> - - <para> - Another variable you can use in your kernel recipe append - file is the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - variable. - When you use this statement, you are extending the locations - used by the OpenEmbedded system to look for files and - patches as the recipe is processed. - </para> - - <note> - <para> - Other methods exist to accomplish grouping and defining - configuration options. - For example, if you are working with a local clone of the - kernel repository, you could checkout the kernel's - <filename>meta</filename> branch, make your changes, and - then push the changes to the local bare clone of the - kernel. - The result is that you directly add configuration options - to the <filename>meta</filename> branch for your BSP. - The configuration options will likely end up in that - location anyway if the BSP gets added to the Yocto Project. - </para> - - <para> - In general, however, the Yocto Project maintainers take - care of moving the <filename>SRC_URI</filename>-specified - configuration options to the kernel's - <filename>meta</filename> branch. - Not only is it easier for BSP developers to not have to - worry about putting those configurations in the branch, - but having the maintainers do it allows them to apply - 'global' knowledge about the kinds of common configuration - options multiple BSPs in the tree are typically using. - This allows for promotion of common configurations into - common features. - </para> - </note> - </section> - - <section id='applying-patches'> - <title>Applying Patches</title> - - <para> - If you have a single patch or a small series of patches - that you want to apply to the Linux kernel source, you - can do so just as you would with any other recipe. - You first copy the patches to the path added to - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - in your <filename>.bbappend</filename> file as described in - the previous section, and then reference them in - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - statements. - </para> - - <para> - For example, you can apply a three-patch series by adding the - following lines to your linux-yocto - <filename>.bbappend</filename> file in your layer: - <literallayout class='monospaced'> - SRC_URI += "file://0001-first-change.patch" - SRC_URI += "file://0002-second-change.patch" - SRC_URI += "file://0003-third-change.patch" - </literallayout> - The next time you run BitBake to build the Linux kernel, - BitBake detects the change in the recipe and fetches and - applies the patches before building the kernel. - </para> - - <para> - For a detailed example showing how to patch the kernel using - <filename>devtool</filename>, see the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - and - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - sections. - </para> - </section> - - <section id='changing-the-configuration'> - <title>Changing the Configuration</title> - - <para> - You can make wholesale or incremental changes to the final - <filename>.config</filename> file used for the eventual - Linux kernel configuration by including a - <filename>defconfig</filename> file and by specifying - configuration fragments in the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - to be applied to that file. - </para> - - <para> - If you have a complete, working Linux kernel - <filename>.config</filename> - file you want to use for the configuration, as before, copy - that file to the appropriate <filename>${PN}</filename> - directory in your layer's - <filename>recipes-kernel/linux</filename> directory, - and rename the copied file to "defconfig". - Then, add the following lines to the linux-yocto - <filename>.bbappend</filename> file in your layer: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - SRC_URI += "file://defconfig" - </literallayout> - The <filename>SRC_URI</filename> tells the build system how to - search for the file, while the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - extends the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink> - variable (search directories) to include the - <filename>${PN}</filename> directory you created to hold the - configuration changes. - </para> - - <note> - The build system applies the configurations from the - <filename>defconfig</filename> file before applying any - subsequent configuration fragments. - The final kernel configuration is a combination of the - configurations in the <filename>defconfig</filename> file and - any configuration fragments you provide. - You need to realize that if you have any configuration - fragments, the build system applies these on top of and - after applying the existing <filename>defconfig</filename> - file configurations. - </note> - - <para> - Generally speaking, the preferred approach is to determine the - incremental change you want to make and add that as a - configuration fragment. - For example, if you want to add support for a basic serial - console, create a file named <filename>8250.cfg</filename> in - the <filename>${PN}</filename> directory with the following - content (without indentation): - <literallayout class='monospaced'> - CONFIG_SERIAL_8250=y - CONFIG_SERIAL_8250_CONSOLE=y - CONFIG_SERIAL_8250_PCI=y - CONFIG_SERIAL_8250_NR_UARTS=4 - CONFIG_SERIAL_8250_RUNTIME_UARTS=4 - CONFIG_SERIAL_CORE=y - CONFIG_SERIAL_CORE_CONSOLE=y - </literallayout> - Next, include this configuration fragment and extend the - <filename>FILESPATH</filename> variable in your - <filename>.bbappend</filename> file: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - SRC_URI += "file://8250.cfg" - </literallayout> - The next time you run BitBake to build the Linux kernel, BitBake - detects the change in the recipe and fetches and applies the - new configuration before building the kernel. - </para> - - <para> - For a detailed example showing how to configure the kernel, - see the - "<link linkend='configuring-the-kernel'>Configuring the Kernel</link>" - section. - </para> - </section> - - <section id='using-an-in-tree-defconfig-file'> - <title>Using an "In-Tree" <filename>defconfig</filename> File</title> - - <para> - It might be desirable to have kernel configuration fragment - support through a <filename>defconfig</filename> file that - is pulled from the kernel source tree for the configured - machine. - By default, the OpenEmbedded build system looks for - <filename>defconfig</filename> files in the layer used for - Metadata, which is "out-of-tree", and then configures them - using the following: - <literallayout class='monospaced'> - SRC_URI += "file://defconfig" - </literallayout> - If you do not want to maintain copies of - <filename>defconfig</filename> files in your layer but would - rather allow users to use the default configuration from the - kernel tree and still be able to add configuration fragments - to the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - through, for example, append files, you can direct the - OpenEmbedded build system to use a - <filename>defconfig</filename> file that is "in-tree". - </para> - - <para> - To specify an "in-tree" <filename>defconfig</filename> file, - use the following statement form: - <literallayout class='monospaced'> - KBUILD_DEFCONFIG_<replaceable>KMACHINE</replaceable> ?= <replaceable>defconfig_file</replaceable> - </literallayout> - Here is an example that assigns the - <filename>KBUILD_DEFCONFIG</filename> variable based on - "raspberrypi2" and provides the path to the "in-tree" - <filename>defconfig</filename> file - to be used for a Raspberry Pi 2, - which is based on the Broadcom 2708/2709 chipset: - <literallayout class='monospaced'> - KBUILD_DEFCONFIG_raspberrypi2 ?= "bcm2709_defconfig" - </literallayout> - </para> - - <para> - Aside from modifying your kernel recipe and providing your own - <filename>defconfig</filename> file, you need to be sure no - files or statements set <filename>SRC_URI</filename> to use a - <filename>defconfig</filename> other than your "in-tree" - file (e.g. a kernel's - <filename>linux-</filename><replaceable>machine</replaceable><filename>.inc</filename> - file). - In other words, if the build system detects a statement - that identifies an "out-of-tree" - <filename>defconfig</filename> file, that statement - will override your - <filename>KBUILD_DEFCONFIG</filename> variable. - </para> - - <para> - See the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KBUILD_DEFCONFIG'><filename>KBUILD_DEFCONFIG</filename></ulink> - variable description for more information. - </para> - </section> - </section> - - <section id="using-devtool-to-patch-the-kernel"> - <title>Using <filename>devtool</filename> to Patch the Kernel</title> - - <para> - The steps in this procedure show you how you can patch the - kernel using the extensible SDK and <filename>devtool</filename>. - <note> - Before attempting this procedure, be sure you have performed - the steps to get ready for updating the kernel as described - in the - "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" - section. - </note> - </para> - - <para> - Patching the kernel involves changing or adding configurations - to an existing kernel, changing or adding recipes to the kernel - that are needed to support specific hardware features, or even - altering the source code itself. - </para> - - <para> - This example creates a simple patch by adding some QEMU emulator - console output at boot time through <filename>printk</filename> - statements in the kernel's <filename>calibrate.c</filename> source - code file. - Applying the patch and booting the modified image causes the added - messages to appear on the emulator's console. - The example is a continuation of the setup procedure found in - the - "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" - Section. - <orderedlist> - <listitem><para> - <emphasis>Check Out the Kernel Source Files:</emphasis> - First you must use <filename>devtool</filename> to checkout - the kernel source code in its workspace. - Be sure you are in the terminal set up to do work - with the extensible SDK. - <note> - See this - <link linkend='setting-up-the-esdk-terminal'>step</link> - in the - "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" - section for more information. - </note> - Use the following <filename>devtool</filename> command - to check out the code: - <literallayout class='monospaced'> - $ devtool modify linux-yocto - </literallayout> - <note> - During the checkout operation, a bug exists that could - cause errors such as the following to appear: - <literallayout class='monospaced'> - ERROR: Taskhash mismatch 2c793438c2d9f8c3681fd5f7bc819efa versus - be3a89ce7c47178880ba7bf6293d7404 for - /path/to/esdk/layers/poky/meta/recipes-kernel/linux/linux-yocto_4.10.bb.do_unpack - </literallayout> - You can safely ignore these messages. - The source code is correctly checked out. - </note> - </para></listitem> - <listitem><para> - <emphasis>Edit the Source Files</emphasis> - Follow these steps to make some simple changes to the source - files: - <orderedlist> - <listitem><para> - <emphasis>Change the working directory</emphasis>: - In the previous step, the output noted where you can find - the source files (e.g. - <filename>~/poky_sdk/workspace/sources/linux-yocto</filename>). - Change to where the kernel source code is before making - your edits to the <filename>calibrate.c</filename> file: - <literallayout class='monospaced'> - $ cd ~/poky_sdk/workspace/sources/linux-yocto - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Edit the source file</emphasis>: - Edit the <filename>init/calibrate.c</filename> file to have - the following changes: - <literallayout class='monospaced'> - void calibrate_delay(void) - { - unsigned long lpj; - static bool printed; - int this_cpu = smp_processor_id(); - - printk("*************************************\n"); - printk("* *\n"); - printk("* HELLO YOCTO KERNEL *\n"); - printk("* *\n"); - printk("*************************************\n"); - - if (per_cpu(cpu_loops_per_jiffy, this_cpu)) { - . - . - . - </literallayout> - </para></listitem> - </orderedlist> - </para></listitem> - <listitem><para> - <emphasis>Build the Updated Kernel Source:</emphasis> - To build the updated kernel source, use - <filename>devtool</filename>: - <literallayout class='monospaced'> - $ devtool build linux-yocto - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create the Image With the New Kernel:</emphasis> - Use the <filename>devtool build-image</filename> command - to create a new image that has the new kernel. - <note> - If the image you originally created resulted in a Wic - file, you can use an alternate method to create the new - image with the updated kernel. - For an example, see the steps in the - <ulink url='https://wiki.yoctoproject.org/wiki/TipsAndTricks/KernelDevelopmentWithEsdk'>TipsAndTricks/KernelDevelopmentWithEsdk</ulink> - Wiki Page. - </note> - <literallayout class='monospaced'> - $ cd ~ - $ devtool build-image core-image-minimal - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Test the New Image:</emphasis> - For this example, you can run the new image using QEMU - to verify your changes: - <orderedlist> - <listitem><para> - <emphasis>Boot the image</emphasis>: - Boot the modified image in the QEMU emulator - using this command: - <literallayout class='monospaced'> - $ runqemu qemux86 - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Verify the changes</emphasis>: - Log into the machine using <filename>root</filename> - with no password and then use the following shell - command to scroll through the console's boot output. - <literallayout class='monospaced'> - # dmesg | less - </literallayout> - You should see the results of your - <filename>printk</filename> statements - as part of the output when you scroll down the - console window. - </para></listitem> - </orderedlist> - </para></listitem> - <listitem><para> - <emphasis>Stage and commit your changes</emphasis>: - Within your eSDK terminal, change your working directory to - where you modified the <filename>calibrate.c</filename> - file and use these Git commands to stage and commit your - changes: - <literallayout class='monospaced'> - $ cd ~/poky_sdk/workspace/sources/linux-yocto - $ git status - $ git add init/calibrate.c - $ git commit -m "calibrate: Add printk example" - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Export the Patches and Create an Append File:</emphasis> - To export your commits as patches and create a - <filename>.bbappend</filename> file, use the following - command in the terminal used to work with the extensible - SDK. - This example uses the previously established layer named - <filename>meta-mylayer</filename>. - <note> - See Step 3 of the - "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using devtool</link>" - section for information on setting up this layer. - </note> - <literallayout class='monospaced'> - $ devtool finish linux-yocto ~/meta-mylayer - </literallayout> - Once the command finishes, the patches and the - <filename>.bbappend</filename> file are located in the - <filename>~/meta-mylayer/recipes-kernel/linux</filename> - directory. - </para></listitem> - <listitem><para> - <emphasis>Build the Image With Your Modified Kernel:</emphasis> - You can now build an image that includes your kernel - patches. - Execute the following command from your - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink> - in the terminal set up to run BitBake: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake core-image-minimal - </literallayout> - </para></listitem> - </orderedlist> - </para> - </section> - - <section id="using-traditional-kernel-development-to-patch-the-kernel"> - <title>Using Traditional Kernel Development to Patch the Kernel</title> - - <para> - The steps in this procedure show you how you can patch the - kernel using traditional kernel development (i.e. not using - <filename>devtool</filename> and the extensible SDK as - described in the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - section). - <note> - Before attempting this procedure, be sure you have performed - the steps to get ready for updating the kernel as described - in the - "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>" - section. - </note> - </para> - - <para> - Patching the kernel involves changing or adding configurations - to an existing kernel, changing or adding recipes to the kernel - that are needed to support specific hardware features, or even - altering the source code itself. - </para> - - <para> - The example in this section creates a simple patch by adding some - QEMU emulator console output at boot time through - <filename>printk</filename> statements in the kernel's - <filename>calibrate.c</filename> source code file. - Applying the patch and booting the modified image causes the added - messages to appear on the emulator's console. - The example is a continuation of the setup procedure found in - the - "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>" - Section. - <orderedlist> - <listitem><para> - <emphasis>Edit the Source Files</emphasis> - Prior to this step, you should have used Git to create a - local copy of the repository for your kernel. - Assuming you created the repository as directed in the - "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>" - section, use the following commands to edit the - <filename>calibrate.c</filename> file: - <orderedlist> - <listitem><para> - <emphasis>Change the working directory</emphasis>: - You need to locate the source files in the - local copy of the kernel Git repository: - Change to where the kernel source code is before making - your edits to the <filename>calibrate.c</filename> file: - <literallayout class='monospaced'> - $ cd ~/linux-yocto-4.12/init - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Edit the source file</emphasis>: - Edit the <filename>calibrate.c</filename> file to have - the following changes: - <literallayout class='monospaced'> - void calibrate_delay(void) - { - unsigned long lpj; - static bool printed; - int this_cpu = smp_processor_id(); - - printk("*************************************\n"); - printk("* *\n"); - printk("* HELLO YOCTO KERNEL *\n"); - printk("* *\n"); - printk("*************************************\n"); - - if (per_cpu(cpu_loops_per_jiffy, this_cpu)) { - . - . - . - </literallayout> - </para></listitem> - </orderedlist> - </para></listitem> - <listitem><para> - <emphasis>Stage and Commit Your Changes:</emphasis> - Use standard Git commands to stage and commit the changes - you just made: - <literallayout class='monospaced'> - $ git add calibrate.c - $ git commit -m "calibrate.c - Added some printk statements" - </literallayout> - If you do not stage and commit your changes, the OpenEmbedded - Build System will not pick up the changes. - </para></listitem> - <listitem><para> - <emphasis>Update Your <filename>local.conf</filename> File - to Point to Your Source Files:</emphasis> - In addition to your <filename>local.conf</filename> file - specifying to use "kernel-modules" and the "qemux86" - machine, it must also point to the updated kernel source - files. - Add - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - and - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRCREV'><filename>SRCREV</filename></ulink> - statements similar to the following to your - <filename>local.conf</filename>: - <literallayout class='monospaced'> - $ cd ~/poky/build/conf - </literallayout> - Add the following to the <filename>local.conf</filename>: - <literallayout class='monospaced'> - SRC_URI_pn-linux-yocto = "git:///<replaceable>path-to</replaceable>/linux-yocto-4.12;protocol=file;name=machine;branch=standard/base; \ - git:///<replaceable>path-to</replaceable>/yocto-kernel-cache;protocol=file;type=kmeta;name=meta;branch=yocto-4.12;destsuffix=${KMETA}" - SRCREV_meta_qemux86 = "${AUTOREV}" - SRCREV_machine_qemux86 = "${AUTOREV}" - </literallayout> - <note> - Be sure to replace - <replaceable>path-to</replaceable> with the pathname - to your local Git repositories. - Also, you must be sure to specify the correct branch - and machine types. - For this example, the branch is - <filename>standard/base</filename> and the machine is - "qemux86". - </note> - </para></listitem> - <listitem><para> - <emphasis>Build the Image:</emphasis> - With the source modified, your changes staged and - committed, and the <filename>local.conf</filename> file - pointing to the kernel files, you can now use BitBake to - build the image: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake core-image-minimal - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Boot the image</emphasis>: - Boot the modified image in the QEMU emulator - using this command. - When prompted to login to the QEMU console, use "root" - with no password: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ runqemu qemux86 - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Look for Your Changes:</emphasis> - As QEMU booted, you might have seen your changes rapidly - scroll by. - If not, use these commands to see your changes: - <literallayout class='monospaced'> - # dmesg | less - </literallayout> - You should see the results of your - <filename>printk</filename> statements - as part of the output when you scroll down the - console window. - </para></listitem> - <listitem><para> - <emphasis>Generate the Patch File:</emphasis> - Once you are sure that your patch works correctly, you - can generate a <filename>*.patch</filename> file in the - kernel source repository: - <literallayout class='monospaced'> - $ cd ~/linux-yocto-4.12/init - $ git format-patch -1 - 0001-calibrate.c-Added-some-printk-statements.patch - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Move the Patch File to Your Layer:</emphasis> - In order for subsequent builds to pick up patches, you - need to move the patch file you created in the previous - step to your layer <filename>meta-mylayer</filename>. - For this example, the layer created earlier is located - in your home directory as <filename>meta-mylayer</filename>. - When the layer was created using the - <filename>yocto-create</filename> script, no additional - hierarchy was created to support patches. - Before moving the patch file, you need to add additional - structure to your layer using the following commands: - <literallayout class='monospaced'> - $ cd ~/meta-mylayer - $ mkdir recipes-kernel - $ mkdir recipes-kernel/linux - $ mkdir recipes-kernel/linux/linux-yocto - </literallayout> - Once you have created this hierarchy in your layer, you can - move the patch file using the following command: - <literallayout class='monospaced'> - $ mv ~/linux-yocto-4.12/init/0001-calibrate.c-Added-some-printk-statements.patch ~/meta-mylayer/recipes-kernel/linux/linux-yocto - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create the Append File:</emphasis> - Finally, you need to create the - <filename>linux-yocto_4.12.bbappend</filename> file and - insert statements that allow the OpenEmbedded build - system to find the patch. - The append file needs to be in your layer's - <filename>recipes-kernel/linux</filename> - directory and it must be named - <filename>linux-yocto_4.12.bbappend</filename> and have - the following contents: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - - SRC_URI_append = " file://0001-calibrate.c-Added-some-printk-statements.patch" - </literallayout> - The - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - and - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - statements enable the OpenEmbedded build system to find - the patch file.</para> - - <para>For more information on append files and patches, - see the - "<link linkend='creating-the-append-file'>Creating the Append File</link>" - and - "<link linkend='applying-patches'>Applying Patches</link>" - sections. - You can also see the - "<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer"</ulink>" - section in the Yocto Project Development Tasks Manual. - <note> - To build <filename>core-image-minimal</filename> - again and see the effects of your patch, you can - essentially eliminate the temporary source files - saved in <filename>poky/build/tmp/work/...</filename> - and residual effects of the build by entering the - following sequence of commands: - <literallayout class='monospaced'> - $ cd ~/poky/build - $ bitbake -c cleanall yocto-linux - $ bitbake core-image-minimal -c cleanall - $ bitbake core-image-minimal - $ runqemu qemux86 - </literallayout> - </note> - </para></listitem> - </orderedlist> - </para> - </section> - - <section id='configuring-the-kernel'> - <title>Configuring the Kernel</title> - - <para> - Configuring the Yocto Project kernel consists of making sure the - <filename>.config</filename> file has all the right information - in it for the image you are building. - You can use the <filename>menuconfig</filename> tool and - configuration fragments to make sure your - <filename>.config</filename> file is just how you need it. - You can also save known configurations in a - <filename>defconfig</filename> file that the build system can use - for kernel configuration. - </para> - - <para> - This section describes how to use <filename>menuconfig</filename>, - create and use configuration fragments, and how to interactively - modify your <filename>.config</filename> file to create the - leanest kernel configuration file possible. - </para> - - <para> - For more information on kernel configuration, see the - "<link linkend='changing-the-configuration'>Changing the Configuration</link>" - section. - </para> - - <section id='using-menuconfig'> - <title>Using <filename>menuconfig</filename></title> - - <para> - The easiest way to define kernel configurations is to set - them through the <filename>menuconfig</filename> tool. - This tool provides an interactive method with which - to set kernel configurations. - For general information on <filename>menuconfig</filename>, see - <ulink url='http://en.wikipedia.org/wiki/Menuconfig'></ulink>. - </para> - - <para> - To use the <filename>menuconfig</filename> tool in the Yocto - Project development environment, you must do the following: - <itemizedlist> - <listitem><para> - Because you launch <filename>menuconfig</filename> - using BitBake, you must be sure to set up your - environment by running the - <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink> - script found in the - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>. - </para></listitem> - <listitem><para> - You must be sure of the state of your build's - configuration in the - <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>. - </para></listitem> - <listitem><para> - Your build host must have the following two packages - installed: - <literallayout class='monospaced'> - libncurses5-dev - libtinfo-dev - </literallayout> - </para></listitem> - </itemizedlist> - </para> - - <para> - The following commands initialize the BitBake environment, - run the - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configme'><filename>do_kernel_configme</filename></ulink> - task, and launch <filename>menuconfig</filename>. - These commands assume the Source Directory's top-level folder - is <filename>~/poky</filename>: - <literallayout class='monospaced'> - $ cd poky - $ source oe-init-build-env - $ bitbake linux-yocto -c kernel_configme -f - $ bitbake linux-yocto -c menuconfig - </literallayout> - Once <filename>menuconfig</filename> comes up, its standard - interface allows you to interactively examine and configure - all the kernel configuration parameters. - After making your changes, simply exit the tool and save your - changes to create an updated version of the - <filename>.config</filename> configuration file. - <note> - You can use the entire <filename>.config</filename> file - as the <filename>defconfig</filename> file. - For information on <filename>defconfig</filename> files, - see the - "<link linkend='changing-the-configuration'>Changing the Configuration</link>", - "<link linkend='using-an-in-tree-defconfig-file'>Using an In-Tree <filename>defconfig</filename> File</link>, - and - "<link linkend='creating-a-defconfig-file'>Creating a <filename>defconfig</filename> File</link>" - sections. - </note> - </para> - - <para> - Consider an example that configures the "CONFIG_SMP" setting - for the <filename>linux-yocto-4.12</filename> kernel. - <note> - The OpenEmbedded build system recognizes this kernel as - <filename>linux-yocto</filename> through Metadata (e.g. - <ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></ulink><filename>_linux-yocto ?= "12.4%"</filename>). - </note> - Once <filename>menuconfig</filename> launches, use the - interface to navigate through the selections to find the - configuration settings in which you are interested. - For this example, you deselect "CONFIG_SMP" by clearing the - "Symmetric Multi-Processing Support" option. - Using the interface, you can find the option under - "Processor Type and Features". - To deselect "CONFIG_SMP", use the arrow keys to - highlight "Symmetric Multi-Processing Support" and enter "N" - to clear the asterisk. - When you are finished, exit out and save the change. - </para> - - <para> - Saving the selections updates the <filename>.config</filename> - configuration file. - This is the file that the OpenEmbedded build system uses to - configure the kernel during the build. - You can find and examine this file in the Build Directory in - <filename>tmp/work/</filename>. - The actual <filename>.config</filename> is located in the - area where the specific kernel is built. - For example, if you were building a Linux Yocto kernel based - on the <filename>linux-yocto-4.12</filename> kernel and you - were building a QEMU image targeted for - <filename>x86</filename> architecture, the - <filename>.config</filename> file would be: - <literallayout class='monospaced'> - poky/build/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+gitAUTOINC+eda4d18... - ...967-r0/linux-qemux86-standard-build/.config - </literallayout> - <note> - The previous example directory is artificially split and - many of the characters in the actual filename are omitted - in order to make it more readable. - Also, depending on the kernel you are using, the exact - pathname might differ. - </note> - </para> - - <para> - Within the <filename>.config</filename> file, you can see the - kernel settings. - For example, the following entry shows that symmetric - multi-processor support is not set: - <literallayout class='monospaced'> - # CONFIG_SMP is not set - </literallayout> - </para> - - <para> - A good method to isolate changed configurations is to use a - combination of the <filename>menuconfig</filename> tool and - simple shell commands. - Before changing configurations with - <filename>menuconfig</filename>, copy the existing - <filename>.config</filename> and rename it to something else, - use <filename>menuconfig</filename> to make as many changes as - you want and save them, then compare the renamed configuration - file against the newly created file. - You can use the resulting differences as your base to create - configuration fragments to permanently save in your kernel - layer. - <note> - Be sure to make a copy of the <filename>.config</filename> - file and do not just rename it. - The build system needs an existing - <filename>.config</filename> file from which to work. - </note> - </para> - </section> - - <section id='creating-a-defconfig-file'> - <title>Creating a <filename>defconfig</filename> File</title> - - <para> - A <filename>defconfig</filename> file in the context of - the Yocto Project is often a <filename>.config</filename> - file that is copied from a build or a - <filename>defconfig</filename> taken from the kernel tree - and moved into recipe space. - You can use a <filename>defconfig</filename> file - to retain a known set of kernel configurations from which the - OpenEmbedded build system can draw to create the final - <filename>.config</filename> file. - <note> - Out-of-the-box, the Yocto Project never ships a - <filename>defconfig</filename> or - <filename>.config</filename> file. - The OpenEmbedded build system creates the final - <filename>.config</filename> file used to configure the - kernel. - </note> - </para> - - <para> - To create a <filename>defconfig</filename>, start with a - complete, working Linux kernel <filename>.config</filename> - file. - Copy that file to the appropriate - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename> - directory in your layer's - <filename>recipes-kernel/linux</filename> directory, and rename - the copied file to "defconfig" (e.g. - <filename>~/meta-mylayer/recipes-kernel/linux/linux-yocto/defconfig</filename>). - Then, add the following lines to the linux-yocto - <filename>.bbappend</filename> file in your layer: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - SRC_URI += "file://defconfig" - </literallayout> - The - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - tells the build system how to search for the file, while the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink> - extends the - <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink> - variable (search directories) to include the - <filename>${PN}</filename> directory you created to hold the - configuration changes. - <note> - The build system applies the configurations from the - <filename>defconfig</filename> file before applying any - subsequent configuration fragments. - The final kernel configuration is a combination of the - configurations in the <filename>defconfig</filename> - file and any configuration fragments you provide. - You need to realize that if you have any configuration - fragments, the build system applies these on top of and - after applying the existing defconfig file configurations. - </note> - For more information on configuring the kernel, see the - "<link linkend='changing-the-configuration'>Changing the Configuration</link>" - section. - </para> - </section> - - <section id='creating-config-fragments'> - <title>Creating Configuration Fragments</title> - - <para> - Configuration fragments are simply kernel options that - appear in a file placed where the OpenEmbedded build system - can find and apply them. - The build system applies configuration fragments after - applying configurations from a <filename>defconfig</filename> - file. - Thus, the final kernel configuration is a combination of the - configurations in the <filename>defconfig</filename> - file and then any configuration fragments you provide. - The build system applies fragments on top of and - after applying the existing defconfig file configurations. - </para> - - <para> - Syntactically, the configuration statement is identical to - what would appear in the <filename>.config</filename> file, - which is in the - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>. - <note> - For more information about where the - <filename>.config</filename> file is located, see the - example in the - "<link linkend='using-menuconfig'>Using <filename>menuconfig</filename></link>" - section. - </note> - </para> - - <para> - It is simple to create a configuration fragment. - One method is to use shell commands. - For example, issuing the following from the shell creates a - configuration fragment file named - <filename>my_smp.cfg</filename> that enables multi-processor - support within the kernel: - <literallayout class='monospaced'> - $ echo "CONFIG_SMP=y" >> my_smp.cfg - </literallayout> - <note> - All configuration fragment files must use the - <filename>.cfg</filename> extension in order for the - OpenEmbedded build system to recognize them as a - configuration fragment. - </note> - </para> - - <para> - Another method is to create a configuration fragment using the - differences between two configuration files: one previously - created and saved, and one freshly created using the - <filename>menuconfig</filename> tool. - </para> - - <para> - To create a configuration fragment using this method, follow - these steps: - <orderedlist> - <listitem><para> - <emphasis>Complete a Build Through Kernel Configuration:</emphasis> - Complete a build at least through the kernel - configuration task as follows: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c kernel_configme -f - </literallayout> - This step ensures that you create a - <filename>.config</filename> file from a known state. - Because situations exist where your build state might - become unknown, it is best to run this task prior - to starting <filename>menuconfig</filename>. - </para></listitem> - <listitem><para> - <emphasis>Launch <filename>menuconfig</filename>:</emphasis> - Run the <filename>menuconfig</filename> command: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c menuconfig - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Create the Configuration Fragment:</emphasis> - Run the <filename>diffconfig</filename> - command to prepare a configuration fragment. - The resulting file <filename>fragment.cfg</filename> - is placed in the - <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}</filename> directory: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c diffconfig - </literallayout> - </para></listitem> - </orderedlist> - </para> - - <para> - The <filename>diffconfig</filename> command creates a file - that is a list of Linux kernel <filename>CONFIG_</filename> - assignments. - See the "<link linkend='changing-the-configuration'>Changing the Configuration</link>" - section for additional information on how to use the output - as a configuration fragment. - <note> - You can also use this method to create configuration - fragments for a BSP. - See the "<link linkend='bsp-descriptions'>BSP Descriptions</link>" - section for more information. - </note> - </para> - - <para> - Where do you put your configuration fragment files? - You can place these files in an area pointed to by - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - as directed by your <filename>bblayers.conf</filename> file, - which is located in your layer. - The OpenEmbedded build system picks up the configuration and - adds it to the kernel's configuration. - For example, suppose you had a set of configuration options - in a file called <filename>myconfig.cfg</filename>. - If you put that file inside a directory named - <filename>linux-yocto</filename> that resides in the same - directory as the kernel's append file within your layer - and then add the following statements to the kernel's append - file, those configuration options will be picked up and applied - when the kernel is built: - <literallayout class='monospaced'> - FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:" - SRC_URI += "file://myconfig.cfg" - </literallayout> - </para> - - <para> - As mentioned earlier, you can group related configurations - into multiple files and name them all in the - <filename>SRC_URI</filename> statement as well. - For example, you could group separate configurations - specifically for Ethernet and graphics into their own files - and add those by using a <filename>SRC_URI</filename> statement - like the following in your append file: - <literallayout class='monospaced'> - SRC_URI += "file://myconfig.cfg \ - file://eth.cfg \ - file://gfx.cfg" - </literallayout> - </para> - </section> - - <section id='validating-configuration'> - <title>Validating Configuration</title> - - <para> - You can use the - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configcheck'><filename>do_kernel_configcheck</filename></ulink> - task to provide configuration validation: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c kernel_configcheck -f - </literallayout> - Running this task produces warnings for when a - requested configuration does not appear in the final - <filename>.config</filename> file or when you override a - policy configuration in a hardware configuration fragment. - </para> - - <para> - In order to run this task, you must have an existing - <filename>.config</filename> file. - See the - "<link linkend='using-menuconfig'>Using <filename>menuconfig</filename></link>" - section for information on how to create a configuration file. - </para> - - <para> - Following is sample output from the - <filename>do_kernel_configcheck</filename> task: - <literallayout class='monospaced'> - Loading cache: 100% |########################################################| Time: 0:00:00 - Loaded 1275 entries from dependency cache. - NOTE: Resolving any missing task queue dependencies - - Build Configuration: - . - . - . - - NOTE: Executing SetScene Tasks - NOTE: Executing RunQueue Tasks - WARNING: linux-yocto-4.12.12+gitAUTOINC+eda4d18ce4_16de014967-r0 do_kernel_configcheck: - [kernel config]: specified values did not make it into the kernel's final configuration: - - ---------- CONFIG_X86_TSC ----------------- - Config: CONFIG_X86_TSC - From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/bsp/common-pc/common-pc-cpu.cfg - Requested value: CONFIG_X86_TSC=y - Actual value: - - - ---------- CONFIG_X86_BIGSMP ----------------- - Config: CONFIG_X86_BIGSMP - From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/cfg/smp.cfg - /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/defconfig - Requested value: # CONFIG_X86_BIGSMP is not set - Actual value: - - - ---------- CONFIG_NR_CPUS ----------------- - Config: CONFIG_NR_CPUS - From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/cfg/smp.cfg - /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/bsp/common-pc/common-pc.cfg - /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/defconfig - Requested value: CONFIG_NR_CPUS=8 - Actual value: CONFIG_NR_CPUS=1 - - - ---------- CONFIG_SCHED_SMT ----------------- - Config: CONFIG_SCHED_SMT - From: /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/cfg/smp.cfg - /home/scottrif/poky/build/tmp/work-shared/qemux86/kernel-source/.kernel-meta/configs/standard/defconfig - Requested value: CONFIG_SCHED_SMT=y - Actual value: - - - - NOTE: Tasks Summary: Attempted 288 tasks of which 285 didn't need to be rerun and all succeeded. - - Summary: There were 3 WARNING messages shown. - </literallayout> - <note> - The previous output example has artificial line breaks - to make it more readable. - </note> - </para> - - <para> - The output describes the various problems that you can - encounter along with where to find the offending configuration - items. - You can use the information in the logs to adjust your - configuration files and then repeat the - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configme'><filename>do_kernel_configme</filename></ulink> - and - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-kernel_configcheck'><filename>do_kernel_configcheck</filename></ulink> - tasks until they produce no warnings. - </para> - - <para> - For more information on how to use the - <filename>menuconfig</filename> tool, see the - "<link linkend='using-menuconfig'>Using <filename>menuconfig</filename></link>" - section. - </para> - </section> - - <section id='fine-tuning-the-kernel-configuration-file'> - <title>Fine-Tuning the Kernel Configuration File</title> - - <para> - You can make sure the <filename>.config</filename> file is as - lean or efficient as possible by reading the output of the - kernel configuration fragment audit, noting any issues, making - changes to correct the issues, and then repeating. - </para> - - <para> - As part of the kernel build process, the - <filename>do_kernel_configcheck</filename> task runs. - This task validates the kernel configuration by checking the - final <filename>.config</filename> file against the input - files. - During the check, the task produces warning messages for the - following issues: - <itemizedlist> - <listitem><para> - Requested options that did not make the final - <filename>.config</filename> file. - </para></listitem> - <listitem><para> - Configuration items that appear twice in the same - configuration fragment. - </para></listitem> - <listitem><para> - Configuration items tagged as "required" that were - overridden. - </para></listitem> - <listitem><para> - A board overrides a non-board specific option. - </para></listitem> - <listitem><para> - Listed options not valid for the kernel being - processed. - In other words, the option does not appear anywhere. - </para></listitem> - </itemizedlist> - <note> - The <filename>do_kernel_configcheck</filename> task can - also optionally report if an option is overridden during - processing. - </note> - </para> - - <para> - For each output warning, a message points to the file - that contains a list of the options and a pointer to the - configuration fragment that defines them. - Collectively, the files are the key to streamlining the - configuration. - </para> - - <para> - To streamline the configuration, do the following: - <orderedlist> - <listitem><para> - <emphasis>Use a Working Configuration:</emphasis> - Start with a full configuration that you - know works. - Be sure the configuration builds and boots - successfully. - Use this configuration file as your baseline. - </para></listitem> - <listitem><para> - <emphasis>Run Configure and Check Tasks:</emphasis> - Separately run the - <filename>do_kernel_configme</filename> and - <filename>do_kernel_configcheck</filename> tasks: - <literallayout class='monospaced'> - $ bitbake linux-yocto -c kernel_configme -f - $ bitbake linux-yocto -c kernel_configcheck -f - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Process the Results:</emphasis> - Take the resulting list of files from the - <filename>do_kernel_configcheck</filename> task - warnings and do the following: - <itemizedlist> - <listitem><para> - Drop values that are redefined in the fragment - but do not change the final - <filename>.config</filename> file. - </para></listitem> - <listitem><para> - Analyze and potentially drop values from the - <filename>.config</filename> file that override - required configurations. - </para></listitem> - <listitem><para> - Analyze and potentially remove non-board - specific options. - </para></listitem> - <listitem><para> - Remove repeated and invalid options. - </para></listitem> - </itemizedlist> - </para></listitem> - <listitem><para> - <emphasis>Re-Run Configure and Check Tasks:</emphasis> - After you have worked through the output of the kernel - configuration audit, you can re-run the - <filename>do_kernel_configme</filename> and - <filename>do_kernel_configcheck</filename> tasks to - see the results of your changes. - If you have more issues, you can deal with them as - described in the previous step. - </para></listitem> - </orderedlist> - </para> - - <para> - Iteratively working through steps two through four eventually - yields a minimal, streamlined configuration file. - Once you have the best <filename>.config</filename>, you can - build the Linux Yocto kernel. - </para> - </section> - </section> - - <section id='expanding-variables'> - <title>Expanding Variables</title> - - <para> - Sometimes it is helpful to determine what a variable expands - to during a build. - You can do examine the values of variables by examining the - output of the <filename>bitbake -e</filename> command. - The output is long and is more easily managed in a text file, - which allows for easy searches: - <literallayout class='monospaced'> - $ bitbake -e virtual/kernel > <replaceable>some_text_file</replaceable> - </literallayout> - Within the text file, you can see exactly how each variable is - expanded and used by the OpenEmbedded build system. - </para> - </section> - - <section id='working-with-a-dirty-kernel-version-string'> - <title>Working with a "Dirty" Kernel Version String</title> - - <para> - If you build a kernel image and the version string has a - "+" or a "-dirty" at the end, uncommitted modifications exist - in the kernel's source directory. - Follow these steps to clean up the version string: - <orderedlist> - <listitem><para> - <emphasis>Discover the Uncommitted Changes:</emphasis> - Go to the kernel's locally cloned Git repository - (source directory) and use the following Git command - to list the files that have been changed, added, or - removed: - <literallayout class='monospaced'> - $ git status - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Commit the Changes:</emphasis> - You should commit those changes to the kernel source - tree regardless of whether or not you will save, - export, or use the changes: - <literallayout class='monospaced'> - $ git add - $ git commit -s -a -m "getting rid of -dirty" - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Rebuild the Kernel Image:</emphasis> - Once you commit the changes, rebuild the kernel.</para> - - <para>Depending on your particular kernel development - workflow, the commands you use to rebuild the - kernel might differ. - For information on building the kernel image when - using <filename>devtool</filename>, see the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - section. - For information on building the kernel image when - using Bitbake, see the - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - section. - </para></listitem> - </orderedlist> - </para> - </section> - - <section id='working-with-your-own-sources'> - <title>Working With Your Own Sources</title> - - <para> - If you cannot work with one of the Linux kernel - versions supported by existing linux-yocto recipes, you can - still make use of the Yocto Project Linux kernel tooling by - working with your own sources. - When you use your own sources, you will not be able to - leverage the existing kernel - <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink> and - stabilization work of the linux-yocto sources. - However, you will be able to manage your own Metadata in the same - format as the linux-yocto sources. - Maintaining format compatibility facilitates converging with - linux-yocto on a future, mutually-supported kernel version. - </para> - - <para> - To help you use your own sources, the Yocto Project provides a - linux-yocto custom recipe - (<filename>linux-yocto-custom.bb</filename>) that uses - <filename>kernel.org</filename> sources - and the Yocto Project Linux kernel tools for managing - kernel Metadata. - You can find this recipe in the - <filename>poky</filename> Git repository of the - Yocto Project <ulink url='&YOCTO_GIT_URL;'>Source Repository</ulink> - at: - <literallayout class="monospaced"> - poky/meta-skeleton/recipes-kernel/linux/linux-yocto-custom.bb - </literallayout> - </para> - - <para> - Here are some basic steps you can use to work with your own - sources: - <orderedlist> - <listitem><para> - <emphasis>Create a Copy of the Kernel Recipe:</emphasis> - Copy the <filename>linux-yocto-custom.bb</filename> - recipe to your layer and give it a meaningful name. - The name should include the version of the Yocto Linux - kernel you are using (e.g. - <filename>linux-yocto-myproject_4.12.bb</filename>, - where "4.12" is the base version of the Linux kernel - with which you would be working). - </para></listitem> - <listitem><para> - <emphasis>Create a Directory for Your Patches:</emphasis> - In the same directory inside your layer, create a matching - directory to store your patches and configuration files - (e.g. <filename>linux-yocto-myproject</filename>). - </para></listitem> - <listitem><para> - <emphasis>Ensure You Have Configurations:</emphasis> - Make sure you have either a <filename>defconfig</filename> - file or configuration fragment files in your layer. - When you use the <filename>linux-yocto-custom.bb</filename> - recipe, you must specify a configuration. - If you do not have a <filename>defconfig</filename> file, - you can run the following: - <literallayout class='monospaced'> - $ make defconfig - </literallayout> - After running the command, copy the resulting - <filename>.config</filename> file to the - <filename>files</filename> directory in your layer - as "defconfig" and then add it to the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - variable in the recipe.</para> - - <para>Running the <filename>make defconfig</filename> - command results in the default configuration for your - architecture as defined by your kernel. - However, no guarantee exists that this configuration is - valid for your use case, or that your board will even boot. - This is particularly true for non-x86 architectures.</para> - - <para>To use non-x86 <filename>defconfig</filename> files, - you need to be more specific and find one that matches your - board (i.e. for arm, you look in - <filename>arch/arm/configs</filename> and use the one that - is the best starting point for your board). - </para></listitem> - <listitem><para> - <emphasis>Edit the Recipe:</emphasis> - Edit the following variables in your recipe as appropriate - for your project: - <itemizedlist> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>: - The <filename>SRC_URI</filename> should specify - a Git repository that uses one of the supported Git - fetcher protocols (i.e. <filename>file</filename>, - <filename>git</filename>, <filename>http</filename>, - and so forth). - The <filename>SRC_URI</filename> variable should - also specify either a <filename>defconfig</filename> - file or some configuration fragment files. - The skeleton recipe provides an example - <filename>SRC_URI</filename> as a syntax reference. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION'><filename>LINUX_VERSION</filename></ulink>: - The Linux kernel version you are using (e.g. - "4.12"). - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-LINUX_VERSION_EXTENSION'><filename>LINUX_VERSION_EXTENSION</filename></ulink>: - The Linux kernel - <filename>CONFIG_LOCALVERSION</filename> that is - compiled into the resulting kernel and visible - through the <filename>uname</filename> command. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRCREV'><filename>SRCREV</filename></ulink>: - The commit ID from which you want to build. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>: - Treat this variable the same as you would in any - other recipe. - Increment the variable to indicate to the - OpenEmbedded build system that the recipe has - changed. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>: - The default <filename>PV</filename> assignment is - typically adequate. - It combines the <filename>LINUX_VERSION</filename> - with the Source Control Manager (SCM) revision - as derived from the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRCPV'><filename>SRCPV</filename></ulink> - variable. - The combined results are a string with the - following form: - <literallayout class='monospaced'> - 3.19.11+git1+68a635bf8dfb64b02263c1ac80c948647cc76d5f_1+218bd8d2022b9852c60d32f0d770931e3cf343e2 - </literallayout> - While lengthy, the extra verbosity in - <filename>PV</filename> helps ensure you are using - the exact sources from which you intend to build. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink>: - A list of the machines supported by your new recipe. - This variable in the example recipe is set - by default to a regular expression that matches - only the empty string, "(^$)". - This default setting triggers an explicit build - failure. - You must change it to match a list of the machines - that your new recipe supports. - For example, to support the - <filename>qemux86</filename> and - <filename>qemux86-64</filename> machines, use - the following form: - <literallayout class='monospaced'> - COMPATIBLE_MACHINE = "qemux86|qemux86-64" - </literallayout> - </para></listitem> - </itemizedlist> - </para></listitem> - <listitem><para> - <emphasis>Customize Your Recipe as Needed:</emphasis> - Provide further customizations to your recipe - as needed just as you would customize an existing - linux-yocto recipe. - See the - "<link linkend='modifying-an-existing-recipe'>Modifying an Existing Recipe</link>" - section for information. - </para></listitem> - </orderedlist> - </para> - </section> - - <section id='working-with-out-of-tree-modules'> - <title>Working with Out-of-Tree Modules</title> - - <para> - This section describes steps to build out-of-tree modules on - your target and describes how to incorporate out-of-tree modules - in the build. - </para> - - <section id='building-out-of-tree-modules-on-the-target'> - <title>Building Out-of-Tree Modules on the Target</title> - - <para> - While the traditional Yocto Project development model would be - to include kernel modules as part of the normal build - process, you might find it useful to build modules on the - target. - This could be the case if your target system is capable - and powerful enough to handle the necessary compilation. - Before deciding to build on your target, however, you should - consider the benefits of using a proper cross-development - environment from your build host. - </para> - - <para> - If you want to be able to build out-of-tree modules on - the target, there are some steps you need to take - on the target that is running your SDK image. - Briefly, the <filename>kernel-dev</filename> package - is installed by default on all - <filename>*.sdk</filename> images and the - <filename>kernel-devsrc</filename> package is installed - on many of the <filename>*.sdk</filename> images. - However, you need to create some scripts prior to - attempting to build the out-of-tree modules on the target - that is running that image. - </para> - - <para> - Prior to attempting to build the out-of-tree modules, - you need to be on the target as root and you need to - change to the <filename>/usr/src/kernel</filename> directory. - Next, <filename>make</filename> the scripts: - <literallayout class='monospaced'> - # cd /usr/src/kernel - # make scripts - </literallayout> - Because all SDK image recipes include - <filename>dev-pkgs</filename>, the - <filename>kernel-dev</filename> packages will be installed - as part of the SDK image and the - <filename>kernel-devsrc</filename> packages will be installed - as part of applicable SDK images. - The SDK uses the scripts when building out-of-tree - modules. - Once you have switched to that directory and created the - scripts, you should be able to build your out-of-tree modules - on the target. - </para> - </section> - - <section id='incorporating-out-of-tree-modules'> - <title>Incorporating Out-of-Tree Modules</title> - - <para> - While it is always preferable to work with sources integrated - into the Linux kernel sources, if you need an external kernel - module, the <filename>hello-mod.bb</filename> recipe is - available as a template from which you can create your - own out-of-tree Linux kernel module recipe. - </para> - - <para> - This template recipe is located in the - <filename>poky</filename> Git repository of the - Yocto Project <ulink url='&YOCTO_GIT_URL;'>Source Repository</ulink> - at: - <literallayout class="monospaced"> - poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb - </literallayout> - </para> - - <para> - To get started, copy this recipe to your layer and give it a - meaningful name (e.g. <filename>mymodule_1.0.bb</filename>). - In the same directory, create a new directory named - <filename>files</filename> where you can store any source files, - patches, or other files necessary for building - the module that do not come with the sources. - Finally, update the recipe as needed for the module. - Typically, you will need to set the following variables: - <itemizedlist> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-DESCRIPTION'><filename>DESCRIPTION</filename></ulink> - </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE*</filename></ulink> - </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink> - </para></listitem> - </itemizedlist> - </para> - - <para> - Depending on the build system used by the module sources, - you might need to make some adjustments. - For example, a typical module <filename>Makefile</filename> - looks much like the one provided with the - <filename>hello-mod</filename> template: - <literallayout class='monospaced'> - obj-m := hello.o - - SRC := $(shell pwd) - - all: - $(MAKE) -C $(KERNEL_SRC) M=$(SRC) - - modules_install: - $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install - ... - </literallayout> - </para> - - <para> - The important point to note here is the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_SRC'><filename>KERNEL_SRC</filename></ulink> - variable. - The - <ulink url='&YOCTO_DOCS_REF_URL;#ref-classes-module'><filename>module</filename></ulink> - class sets this variable and the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_PATH'><filename>KERNEL_PATH</filename></ulink> - variable to - <filename>${<ulink url='&YOCTO_DOCS_REF_URL;#var-STAGING_KERNEL_DIR'><filename>STAGING_KERNEL_DIR</filename></ulink>}</filename> - with the necessary Linux kernel build information to build - modules. - If your module <filename>Makefile</filename> uses a different - variable, you might want to override the - <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-compile'><filename>do_compile</filename></ulink> - step, or create a patch to - the <filename>Makefile</filename> to work with the more typical - <filename>KERNEL_SRC</filename> or - <filename>KERNEL_PATH</filename> variables. - </para> - - <para> - After you have prepared your recipe, you will likely want to - include the module in your images. - To do this, see the documentation for the following variables in - the Yocto Project Reference Manual and set one of them - appropriately for your machine configuration file: - <itemizedlist> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</filename></ulink> - </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink> - </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RDEPENDS'><filename>MACHINE_EXTRA_RDEPENDS</filename></ulink> - </para></listitem> - <listitem><para><ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RRECOMMENDS'><filename>MACHINE_EXTRA_RRECOMMENDS</filename></ulink> - </para></listitem> - </itemizedlist> - </para> - - <para> - Modules are often not required for boot and can be excluded from - certain build configurations. - The following allows for the most flexibility: - <literallayout class='monospaced'> - MACHINE_EXTRA_RRECOMMENDS += "kernel-module-mymodule" - </literallayout> - The value is derived by appending the module filename without - the <filename>.ko</filename> extension to the string - "kernel-module-". - </para> - - <para> - Because the variable is - <ulink url='&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS'><filename>RRECOMMENDS</filename></ulink> - and not a - <ulink url='&YOCTO_DOCS_REF_URL;#var-RDEPENDS'><filename>RDEPENDS</filename></ulink> - variable, the build will not fail if this module is not - available to include in the image. - </para> - </section> - </section> - - - <section id='inspecting-changes-and-commits'> - <title>Inspecting Changes and Commits</title> - - <para> - A common question when working with a kernel is: - "What changes have been applied to this tree?" - Rather than using "grep" across directories to see what has - changed, you can use Git to inspect or search the kernel tree. - Using Git is an efficient way to see what has changed in the tree. - </para> - - <section id='what-changed-in-a-kernel'> - <title>What Changed in a Kernel?</title> - - <para> - Following are a few examples that show how to use Git - commands to examine changes. - These examples are by no means the only way to see changes. - <note> - In the following examples, unless you provide a commit - range, <filename>kernel.org</filename> history is blended - with Yocto Project kernel changes. - You can form ranges by using branch names from the - kernel tree as the upper and lower commit markers with - the Git commands. - You can see the branch names through the web interface - to the Yocto Project source repositories at - <ulink url='&YOCTO_GIT_URL;'></ulink>. - </note> - To see a full range of the changes, use the - <filename>git whatchanged</filename> command and specify a - commit range for the branch - (<replaceable>commit</replaceable><filename>..</filename><replaceable>commit</replaceable>). - </para> - - <para> - Here is an example that looks at what has changed in the - <filename>emenlow</filename> branch of the - <filename>linux-yocto-3.19</filename> kernel. - The lower commit range is the commit associated with the - <filename>standard/base</filename> branch, while - the upper commit range is the commit associated with the - <filename>standard/emenlow</filename> branch. - <literallayout class='monospaced'> - $ git whatchanged origin/standard/base..origin/standard/emenlow - </literallayout> - </para> - - <para> - To see short, one line summaries of changes use the - <filename>git log</filename> command: - <literallayout class='monospaced'> - $ git log --oneline origin/standard/base..origin/standard/emenlow - </literallayout> - </para> - - <para> - Use this command to see code differences for the changes: - <literallayout class='monospaced'> - $ git diff origin/standard/base..origin/standard/emenlow - </literallayout> - </para> - - <para> - Use this command to see the commit log messages and the - text differences: - <literallayout class='monospaced'> - $ git show origin/standard/base..origin/standard/emenlow - </literallayout> - </para> - - <para> - Use this command to create individual patches for - each change. - Here is an example that that creates patch files for each - commit and places them in your <filename>Documents</filename> - directory: - <literallayout class='monospaced'> - $ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow - </literallayout> - </para> - </section> - - <section id='showing-a-particular-feature-or-branch-change'> - <title>Showing a Particular Feature or Branch Change</title> - - <para> - Tags in the Yocto Project kernel tree divide changes for - significant features or branches. - The <filename>git show</filename> <replaceable>tag</replaceable> - command shows changes based on a tag. - Here is an example that shows <filename>systemtap</filename> - changes: - <literallayout class='monospaced'> - $ git show systemtap - </literallayout> - You can use the - <filename>git branch --contains</filename> <replaceable>tag</replaceable> - command to show the branches that contain a particular feature. - This command shows the branches that contain the - <filename>systemtap</filename> feature: - <literallayout class='monospaced'> - $ git branch --contains systemtap - </literallayout> - </para> - </section> - </section> - - <section id='adding-recipe-space-kernel-features'> - <title>Adding Recipe-Space Kernel Features</title> - - <para> - You can add kernel features in the - <link linkend='recipe-space-metadata'>recipe-space</link> by - using the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink> - variable and by specifying the feature's <filename>.scc</filename> - file path in the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - statement. - When you add features using this method, the OpenEmbedded build - system checks to be sure the features are present. - If the features are not present, the build stops. - Kernel features are the last elements processed for configuring - and patching the kernel. - Therefore, adding features in this manner is a way - to enforce specific features are present and enabled - without needing to do a full audit of any other layer's additions - to the <filename>SRC_URI</filename> statement. - </para> - - <para> - You add a kernel feature by providing the feature as part of the - <filename>KERNEL_FEATURES</filename> variable and by providing the - path to the feature's <filename>.scc</filename> file, which is - relative to the root of the kernel Metadata. - The OpenEmbedded build system searches all forms of kernel - Metadata on the <filename>SRC_URI</filename> statement regardless - of whether the Metadata is in the "kernel-cache", system kernel - Metadata, or a recipe-space Metadata (i.e. part of the kernel - recipe). - See the - "<link linkend='kernel-metadata-location'>Kernel Metadata Location</link>" - section for additional information. - </para> - - <para> - When you specify the feature's <filename>.scc</filename> file - on the <filename>SRC_URI</filename> statement, the OpenEmbedded - build system adds the directory of that - <filename>.scc</filename> file along with all its subdirectories - to the kernel feature search path. - Because subdirectories are searched, you can reference a single - <filename>.scc</filename> file in the - <filename>SRC_URI</filename> statement to reference multiple kernel - features. - </para> - - <para> - Consider the following example that adds the "test.scc" feature - to the build. - <orderedlist> - <listitem><para> - <emphasis>Create the Feature File:</emphasis> - Create a <filename>.scc</filename> file and locate it - just as you would any other patch file, - <filename>.cfg</filename> file, or fetcher item - you specify in the <filename>SRC_URI</filename> - statement. - <note><title>Notes</title> - <itemizedlist> - <listitem><para> - You must add the directory of the - <filename>.scc</filename> file to the fetcher's - search path in the same manner as you would - add a <filename>.patch</filename> file. - </para></listitem> - <listitem><para> - You can create additional - <filename>.scc</filename> files beneath the - directory that contains the file you are - adding. - All subdirectories are searched during the - build as potential feature directories. - </para></listitem> - </itemizedlist> - </note> - Continuing with the example, suppose the "test.scc" - feature you are adding has a - <filename>test.scc</filename> file in the following - directory: - <literallayout class='monospaced'> - <replaceable>my_recipe</replaceable> - | - +-linux-yocto - | - +-test.cfg - +-test.scc - </literallayout> - In this example, the <filename>linux-yocto</filename> - directory has both the feature - <filename>test.scc</filename> file and a similarly - named configuration fragment file - <filename>test.cfg</filename>. - </para></listitem> - <listitem><para> - <emphasis>Add the Feature File to <filename>SRC_URI</filename>:</emphasis> - Add the <filename>.scc</filename> file to the - recipe's <filename>SRC_URI</filename> statement: - <literallayout class='monospaced'> - SRC_URI_append = " file://test.scc" - </literallayout> - The leading space before the path is important as the - path is appended to the existing path. - </para></listitem> - <listitem><para> - <emphasis>Specify the Feature as a Kernel Feature:</emphasis> - Use the <filename>KERNEL_FEATURES</filename> statement - to specify the feature as a kernel feature: - <literallayout class='monospaced'> - KERNEL_FEATURES_append = " test.scc" - </literallayout> - The OpenEmbedded build system processes the kernel feature - when it builds the kernel. - <note> - If other features are contained below "test.scc", - then their directories are relative to the directory - containing the <filename>test.scc</filename> file. - </note> - </para></listitem> - </orderedlist> - </para> - </section> -</chapter> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-concepts-appx.xml b/documentation/kernel-dev/kernel-dev-concepts-appx.xml deleted file mode 100644 index bf0c525caf..0000000000 --- a/documentation/kernel-dev/kernel-dev-concepts-appx.xml +++ /dev/null @@ -1,622 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<appendix id='kernel-dev-concepts-appx'> -<title>Advanced Kernel Concepts</title> - - <section id='kernel-big-picture'> - <title>Yocto Project Kernel Development and Maintenance</title> - - <para> - Kernels available through the Yocto Project (Yocto Linux kernels), - like other kernels, are based off the Linux kernel releases from - <ulink url='http://www.kernel.org'></ulink>. - At the beginning of a major Linux kernel development cycle, the - Yocto Project team chooses a Linux kernel based on factors such as - release timing, the anticipated release timing of final upstream - <filename>kernel.org</filename> versions, and Yocto Project - feature requirements. - Typically, the Linux kernel chosen is in the final stages of - development by the Linux community. - In other words, the Linux kernel is in the release candidate - or "rc" phase and has yet to reach final release. - But, by being in the final stages of external development, the - team knows that the <filename>kernel.org</filename> final release - will clearly be within the early stages of the Yocto Project - development window. - </para> - - <para> - This balance allows the Yocto Project team to deliver the most - up-to-date Yocto Linux kernel possible, while still ensuring that - the team has a stable official release for the baseline Linux - kernel version. - </para> - - <para> - As implied earlier, the ultimate source for Yocto Linux kernels - are released kernels from <filename>kernel.org</filename>. - In addition to a foundational kernel from - <filename>kernel.org</filename>, the available Yocto Linux kernels - contain a mix of important new mainline developments, non-mainline - developments (when no alternative exists), Board Support Package - (BSP) developments, and custom features. - These additions result in a commercially released Yocto - Project Linux kernel that caters to specific embedded designer - needs for targeted hardware. - </para> - - <para> - You can find a web interface to the Yocto Linux kernels in the - <ulink url='&YOCTO_DOCS_OM_URL;#source-repositories'>Source Repositories</ulink> - at - <ulink url='&YOCTO_GIT_URL;'></ulink>. - If you look at the interface, you will see to the left a - grouping of Git repositories titled "Yocto Linux Kernel". - Within this group, you will find several Linux Yocto kernels - developed and included with Yocto Project releases: - <itemizedlist> - <listitem><para> - <emphasis><filename>linux-yocto-4.1</filename>:</emphasis> - The stable Yocto Project kernel to use with the Yocto - Project Release 2.0. - This kernel is based on the Linux 4.1 released kernel. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-4.4</filename>:</emphasis> - The stable Yocto Project kernel to use with the Yocto - Project Release 2.1. - This kernel is based on the Linux 4.4 released kernel. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-4.6</filename>:</emphasis> - A temporary kernel that is not tied to any Yocto Project - release. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-4.8</filename>:</emphasis> - The stable yocto Project kernel to use with the Yocto - Project Release 2.2. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-4.9</filename>:</emphasis> - The stable Yocto Project kernel to use with the Yocto - Project Release 2.3. - This kernel is based on the Linux 4.9 released kernel. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-4.10</filename>:</emphasis> - The default stable Yocto Project kernel to use with the - Yocto Project Release 2.3. - This kernel is based on the Linux 4.10 released kernel. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-4.12</filename>:</emphasis> - The default stable Yocto Project kernel to use with the - Yocto Project Release 2.4. - This kernel is based on the Linux 4.12 released kernel. - </para></listitem> - <listitem><para> - <emphasis><filename>yocto-kernel-cache</filename>:</emphasis> - The <filename>linux-yocto-cache</filename> contains - patches and configurations for the linux-yocto kernel - tree. - This repository is useful when working on the linux-yocto - kernel. - For more information on this "Advanced Kernel Metadata", - see the - "<link linkend='kernel-dev-advanced'>Working With Advanced Metadata (<filename>yocto-kernel-cache</filename>)</link>" - Chapter. - </para></listitem> - <listitem><para> - <emphasis><filename>linux-yocto-dev</filename>:</emphasis> - A development kernel based on the latest upstream release - candidate available. - </para></listitem> - </itemizedlist> - <note><title>Notes</title> - Long Term Support Initiative (LTSI) for Yocto Linux - kernels is as follows: - <itemizedlist> - <listitem><para> - For Yocto Project releases 1.7, 1.8, and 2.0, - the LTSI kernel is - <filename>linux-yocto-3.14</filename>. - </para></listitem> - <listitem><para> - For Yocto Project releases 2.1, 2.2, and 2.3, - the LTSI kernel is <filename>linux-yocto-4.1</filename>. - </para></listitem> - <listitem><para> - For Yocto Project release 2.4, the LTSI kernel is - <filename>linux-yocto-4.9</filename> - </para></listitem> - <listitem><para> - <filename>linux-yocto-4.4</filename> is an LTS - kernel. - </para></listitem> - </itemizedlist> - </note> - </para> - - <para> - Once a Yocto Linux kernel is officially released, the Yocto - Project team goes into their next development cycle, or upward - revision (uprev) cycle, while still continuing maintenance on the - released kernel. - It is important to note that the most sustainable and stable way - to include feature development upstream is through a kernel uprev - process. - Back-porting hundreds of individual fixes and minor features from - various kernel versions is not sustainable and can easily - compromise quality. - </para> - - <para> - During the uprev cycle, the Yocto Project team uses an ongoing - analysis of Linux kernel development, BSP support, and release - timing to select the best possible <filename>kernel.org</filename> - Linux kernel version on which to base subsequent Yocto Linux - kernel development. - The team continually monitors Linux community kernel development - to look for significant features of interest. - The team does consider back-porting large features if they have a - significant advantage. - User or community demand can also trigger a back-port or creation - of new functionality in the Yocto Project baseline kernel during - the uprev cycle. - </para> - - <para> - Generally speaking, every new Linux kernel both adds features and - introduces new bugs. - These consequences are the basic properties of upstream - Linux kernel development and are managed by the Yocto Project - team's Yocto Linux kernel development strategy. - It is the Yocto Project team's policy to not back-port minor - features to the released Yocto Linux kernel. - They only consider back-porting significant technological - jumps ‐ and, that is done after a complete gap analysis. - The reason for this policy is that back-porting any small to - medium sized change from an evolving Linux kernel can easily - create mismatches, incompatibilities and very subtle errors. - </para> - - <para> - The policies described in this section result in both a stable - and a cutting edge Yocto Linux kernel that mixes forward ports of - existing Linux kernel features and significant and critical new - functionality. - Forward porting Linux kernel functionality into the Yocto Linux - kernels available through the Yocto Project can be thought of as - a "micro uprev." - The many "micro uprevs" produce a Yocto Linux kernel version with - a mix of important new mainline, non-mainline, BSP developments - and feature integrations. - This Yocto Linux kernel gives insight into new features and - allows focused amounts of testing to be done on the kernel, - which prevents surprises when selecting the next major uprev. - The quality of these cutting edge Yocto Linux kernels is evolving - and the kernels are used in leading edge feature and BSP - development. - </para> - </section> - - <section id='yocto-linux-kernel-architecture-and-branching-strategies'> - <title>Yocto Linux Kernel Architecture and Branching Strategies</title> - - <para> - As mentioned earlier, a key goal of the Yocto Project is - to present the developer with a kernel that has a clear and - continuous history that is visible to the user. - The architecture and mechanisms, in particular the branching - strategies, used achieve that goal in a manner similar to - upstream Linux kernel development in - <filename>kernel.org</filename>. - </para> - - <para> - You can think of a Yocto Linux kernel as consisting of a - baseline Linux kernel with added features logically structured - on top of the baseline. - The features are tagged and organized by way of a branching - strategy implemented by the Yocto Project team using the - Source Code Manager (SCM) Git. - <note><title>Notes</title> - <itemizedlist> - <listitem><para> - Git is the obvious SCM for meeting the Yocto Linux - kernel organizational and structural goals described - in this section. - Not only is Git the SCM for Linux kernel development in - <filename>kernel.org</filename> but, Git continues to - grow in popularity and supports many different work - flows, front-ends and management techniques. - </para></listitem> - <listitem><para> - You can find documentation on Git at - <ulink url='http://git-scm.com/documentation'></ulink>. - You can also get an introduction to Git as it - applies to the Yocto Project in the - "<ulink url='&YOCTO_DOCS_OM_URL;#git'>Git</ulink>" - section in the Yocto Project Overview and Concepts - Manual. - The latter reference provides an overview of - Git and presents a minimal set of Git commands - that allows you to be functional using Git. - You can use as much, or as little, of what Git - has to offer to accomplish what you need for your - project. - You do not have to be a "Git Expert" in order to - use it with the Yocto Project. - </para></listitem> - </itemizedlist> - </note> - </para> - - <para> - Using Git's tagging and branching features, the Yocto Project - team creates kernel branches at points where functionality is - no longer shared and thus, needs to be isolated. - For example, board-specific incompatibilities would require - different functionality and would require a branch to - separate the features. - Likewise, for specific kernel features, the same branching - strategy is used. - </para> - - <para> - This "tree-like" architecture results in a structure that has - features organized to be specific for particular functionality, - single kernel types, or a subset of kernel types. - Thus, the user has the ability to see the added features and the - commits that make up those features. - In addition to being able to see added features, the user - can also view the history of what made up the baseline - Linux kernel. - </para> - - <para> - Another consequence of this strategy results in not having to - store the same feature twice internally in the tree. - Rather, the kernel team stores the unique differences required - to apply the feature onto the kernel type in question. - <note> - The Yocto Project team strives to place features in the tree - such that features can be shared by all boards and kernel - types where possible. - However, during development cycles or when large features - are merged, the team cannot always follow this practice. - In those cases, the team uses isolated branches to merge - features. - </note> - </para> - - <para> - BSP-specific code additions are handled in a similar manner to - kernel-specific additions. - Some BSPs only make sense given certain kernel types. - So, for these types, the team creates branches off the end - of that kernel type for all of the BSPs that are supported on - that kernel type. - From the perspective of the tools that create the BSP branch, - the BSP is really no different than a feature. - Consequently, the same branching strategy applies to BSPs as - it does to kernel features. - So again, rather than store the BSP twice, the team only - stores the unique differences for the BSP across the supported - multiple kernels. - </para> - - <para> - While this strategy can result in a tree with a significant number - of branches, it is important to realize that from the developer's - point of view, there is a linear path that travels from the - baseline <filename>kernel.org</filename>, through a select - group of features and ends with their BSP-specific commits. - In other words, the divisions of the kernel are transparent and - are not relevant to the developer on a day-to-day basis. - From the developer's perspective, this path is the "master" branch - in Git terms. - The developer does not need to be aware of the existence of any - other branches at all. - Of course, value exists in the having these branches in the tree, - should a person decide to explore them. - For example, a comparison between two BSPs at either the commit - level or at the line-by-line code <filename>diff</filename> level - is now a trivial operation. - </para> - - <para> - The following illustration shows the conceptual Yocto - Linux kernel. - <imagedata fileref="figures/kernel-architecture-overview.png" width="6in" depth="7in" align="center" scale="100" /> - </para> - - <para> - In the illustration, the "Kernel.org Branch Point" marks the - specific spot (or Linux kernel release) from which the - Yocto Linux kernel is created. - From this point forward in the tree, features and differences - are organized and tagged. - </para> - - <para> - The "Yocto Project Baseline Kernel" contains functionality that - is common to every kernel type and BSP that is organized - further along in the tree. - Placing these common features in the tree this way means - features do not have to be duplicated along individual - branches of the tree structure. - </para> - - <para> - From the "Yocto Project Baseline Kernel", branch points represent - specific functionality for individual Board Support Packages - (BSPs) as well as real-time kernels. - The illustration represents this through three BSP-specific - branches and a real-time kernel branch. - Each branch represents some unique functionality for the BSP - or for a real-time Yocto Linux kernel. - </para> - - <para> - In this example structure, the "Real-time (rt) Kernel" branch has - common features for all real-time Yocto Linux kernels and - contains more branches for individual BSP-specific real-time - kernels. - The illustration shows three branches as an example. - Each branch points the way to specific, unique features for a - respective real-time kernel as they apply to a given BSP. - </para> - - <para> - The resulting tree structure presents a clear path of markers - (or branches) to the developer that, for all practical - purposes, is the Yocto Linux kernel needed for any given set of - requirements. - <note> - Keep in mind the figure does not take into account all the - supported Yocto Linux kernels, but rather shows a single - generic kernel just for conceptual purposes. - Also keep in mind that this structure represents the Yocto - Project - <ulink url='&YOCTO_DOCS_OM_URL;#source-repositories'>Source Repositories</ulink> - that are either pulled from during the build or established - on the host development system prior to the build by either - cloning a particular kernel's Git repository or by - downloading and unpacking a tarball. - </note> - </para> - - <para> - Working with the kernel as a structured tree follows recognized - community best practices. - In particular, the kernel as shipped with the product, should be - considered an "upstream source" and viewed as a series of - historical and documented modifications (commits). - These modifications represent the development and stabilization - done by the Yocto Project kernel development team. - </para> - - <para> - Because commits only change at significant release points in the - product life cycle, developers can work on a branch created - from the last relevant commit in the shipped Yocto Project Linux - kernel. - As mentioned previously, the structure is transparent to the - developer because the kernel tree is left in this state after - cloning and building the kernel. - </para> - </section> - - <section id='kernel-build-file-hierarchy'> - <title>Kernel Build File Hierarchy</title> - - <para> - Upstream storage of all the available kernel source code is - one thing, while representing and using the code on your host - development system is another. - Conceptually, you can think of the kernel source repositories - as all the source files necessary for all the supported - Yocto Linux kernels. - As a developer, you are just interested in the source files - for the kernel on which you are working. - And, furthermore, you need them available on your host system. - </para> - - <para> - Kernel source code is available on your host system several - different ways: - <itemizedlist> - <listitem><para> - <emphasis>Files Accessed While using <filename>devtool</filename>:</emphasis> - <filename>devtool</filename>, which is available with the - Yocto Project, is the preferred method by which to - modify the kernel. - See the - "<link linkend='kernel-modification-workflow'>Kernel Modification Workflow</link>" - section. - </para></listitem> - <listitem><para> - <emphasis>Cloned Repository:</emphasis> - If you are working in the kernel all the time, you probably - would want to set up your own local Git repository of the - Yocto Linux kernel tree. - For information on how to clone a Yocto Linux kernel - Git repository, see the - "<link linkend='preparing-the-build-host-to-work-on-the-kernel'>Preparing the Build Host to Work on the Kernel</link>" - section. - </para></listitem> - <listitem><para> - <emphasis>Temporary Source Files from a Build:</emphasis> - If you just need to make some patches to the kernel using - a traditional BitBake workflow (i.e. not using the - <filename>devtool</filename>), you can access temporary - kernel source files that were extracted and used during - a kernel build. - </para></listitem> - </itemizedlist> - </para> - - <para> - The temporary kernel source files resulting from a build using - BitBake have a particular hierarchy. - When you build the kernel on your development system, all files - needed for the build are taken from the source repositories - pointed to by the - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - variable and gathered in a temporary work area where they are - subsequently used to create the unique kernel. - Thus, in a sense, the process constructs a local source tree - specific to your kernel from which to generate the new kernel - image. - </para> - - <para> - The following figure shows the temporary file structure - created on your host system when you build the kernel using - Bitbake. - This - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink> - contains all the source files used during the build. - <imagedata fileref="figures/kernel-overview-2-generic.png" - width="6in" depth="5in" align="center" scale="100" /> - </para> - - <para> - Again, for additional information on the Yocto Project kernel's - architecture and its branching strategy, see the - "<link linkend='yocto-linux-kernel-architecture-and-branching-strategies'>Yocto Linux Kernel Architecture and Branching Strategies</link>" - section. - You can also reference the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - and - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - sections for detailed example that modifies the kernel. - </para> - </section> - - <section id='determining-hardware-and-non-hardware-features-for-the-kernel-configuration-audit-phase'> - <title>Determining Hardware and Non-Hardware Features for the Kernel Configuration Audit Phase</title> - - <para> - This section describes part of the kernel configuration audit - phase that most developers can ignore. - For general information on kernel configuration including - <filename>menuconfig</filename>, <filename>defconfig</filename> - files, and configuration fragments, see the - "<link linkend='configuring-the-kernel'>Configuring the Kernel</link>" - section. - </para> - - <para> - During this part of the audit phase, the contents of the final - <filename>.config</filename> file are compared against the - fragments specified by the system. - These fragments can be system fragments, distro fragments, - or user-specified configuration elements. - Regardless of their origin, the OpenEmbedded build system - warns the user if a specific option is not included in the - final kernel configuration. - </para> - - <para> - By default, in order to not overwhelm the user with - configuration warnings, the system only reports missing - "hardware" options as they could result in a boot - failure or indicate that important hardware is not available. - </para> - - <para> - To determine whether or not a given option is "hardware" or - "non-hardware", the kernel Metadata in - <filename>yocto-kernel-cache</filename> contains files that - classify individual or groups of options as either hardware - or non-hardware. - To better show this, consider a situation where the - <filename>yocto-kernel-cache</filename> contains the following - files: - <literallayout class='monospaced'> - yocto-kernel-cache/features/drm-psb/hardware.cfg - yocto-kernel-cache/features/kgdb/hardware.cfg - yocto-kernel-cache/ktypes/base/hardware.cfg - yocto-kernel-cache/bsp/mti-malta32/hardware.cfg - yocto-kernel-cache/bsp/qemu-ppc32/hardware.cfg - yocto-kernel-cache/bsp/qemuarma9/hardware.cfg - yocto-kernel-cache/bsp/mti-malta64/hardware.cfg - yocto-kernel-cache/bsp/arm-versatile-926ejs/hardware.cfg - yocto-kernel-cache/bsp/common-pc/hardware.cfg - yocto-kernel-cache/bsp/common-pc-64/hardware.cfg - yocto-kernel-cache/features/rfkill/non-hardware.cfg - yocto-kernel-cache/ktypes/base/non-hardware.cfg - yocto-kernel-cache/features/aufs/non-hardware.kcf - yocto-kernel-cache/features/ocf/non-hardware.kcf - yocto-kernel-cache/ktypes/base/non-hardware.kcf - yocto-kernel-cache/ktypes/base/hardware.kcf - yocto-kernel-cache/bsp/qemu-ppc32/hardware.kcf - </literallayout> - The following list provides explanations for the various - files: - <itemizedlist> - <listitem><para> - <filename>hardware.kcf</filename>: - Specifies a list of kernel Kconfig files that contain - hardware options only. - </para></listitem> - <listitem><para> - <filename>non-hardware.kcf</filename>: - Specifies a list of kernel Kconfig files that contain - non-hardware options only. - </para></listitem> - <listitem><para> - <filename>hardware.cfg</filename>: - Specifies a list of kernel <filename>CONFIG_</filename> - options that are hardware, regardless of whether or not - they are within a Kconfig file specified by a hardware - or non-hardware Kconfig file (i.e. - <filename>hardware.kcf</filename> or - <filename>non-hardware.kcf</filename>). - </para></listitem> - <listitem><para> - <filename>non-hardware.cfg</filename>: - Specifies a list of kernel <filename>CONFIG_</filename> - options that are not hardware, regardless of whether or - not they are within a Kconfig file specified by a - hardware or non-hardware Kconfig file (i.e. - <filename>hardware.kcf</filename> or - <filename>non-hardware.kcf</filename>). - </para></listitem> - </itemizedlist> - Here is a specific example using the - <filename>kernel-cache/bsp/mti-malta32/hardware.cfg</filename>: - <literallayout class='monospaced'> - CONFIG_SERIAL_8250 - CONFIG_SERIAL_8250_CONSOLE - CONFIG_SERIAL_8250_NR_UARTS - CONFIG_SERIAL_8250_PCI - CONFIG_SERIAL_CORE - CONFIG_SERIAL_CORE_CONSOLE - CONFIG_VGA_ARB - </literallayout> - The kernel configuration audit automatically detects these - files (hence the names must be exactly the ones discussed here), - and uses them as inputs when generating warnings about the - final <filename>.config</filename> file. - </para> - - <para> - A user-specified kernel Metadata repository, or recipe space - feature, can use these same files to classify options that are - found within its <filename>.cfg</filename> files as hardware - or non-hardware, to prevent the OpenEmbedded build system from - producing an error or warning when an option is not in the - final <filename>.config</filename> file. - </para> - </section> -</appendix> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-customization.xsl b/documentation/kernel-dev/kernel-dev-customization.xsl deleted file mode 100644 index 88bf7c678a..0000000000 --- a/documentation/kernel-dev/kernel-dev-customization.xsl +++ /dev/null @@ -1,28 +0,0 @@ -<?xml version='1.0'?> -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml" xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0"> - - <xsl:import href="http://downloads.yoctoproject.org/mirror/docbook-mirror/docbook-xsl-1.76.1/xhtml/docbook.xsl" /> - -<!-- - - <xsl:import href="../template/1.76.1/docbook-xsl-1.76.1/xhtml/docbook.xsl" /> - - <xsl:import href="http://docbook.sourceforge.net/release/xsl/1.76.1/xhtml/docbook.xsl" /> - ---> - - <xsl:include href="../template/permalinks.xsl"/> - <xsl:include href="../template/section.title.xsl"/> - <xsl:include href="../template/component.title.xsl"/> - <xsl:include href="../template/division.title.xsl"/> - <xsl:include href="../template/formal.object.heading.xsl"/> - - <xsl:param name="html.stylesheet" select="'kernel-dev-style.css'" /> - <xsl:param name="chapter.autolabel" select="1" /> - <xsl:param name="appendix.autolabel">A</xsl:param> - <xsl:param name="section.autolabel" select="1" /> - <xsl:param name="section.label.includes.component.label" select="1" /> - -</xsl:stylesheet> diff --git a/documentation/kernel-dev/kernel-dev-faq.xml b/documentation/kernel-dev/kernel-dev-faq.xml deleted file mode 100644 index d76f0a4e32..0000000000 --- a/documentation/kernel-dev/kernel-dev-faq.xml +++ /dev/null @@ -1,143 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<appendix id='kernel-dev-faq'> -<title>Kernel Development FAQ</title> - -<section id='kernel-dev-faq-section'> - <title>Common Questions and Solutions</title> - - <para> - The following lists some solutions for common questions. - - - <qandaset> - <qandaentry> - <question> - <para> - How do I use my own Linux kernel <filename>.config</filename> - file? - </para> - </question> - <answer> - <para> - Refer to the "<link linkend='changing-the-configuration'>Changing the Configuration</link>" - section for information. - </para> - </answer> - </qandaentry> - - <qandaentry> - <question> - <para> - How do I create configuration fragments? - </para> - </question> - <answer> - <para> - Refer to the - "<link linkend='creating-config-fragments'>Creating Configuration Fragments</link>" - section for information. - </para> - </answer> - </qandaentry> - - <qandaentry> - <question> - <para> - How do I use my own Linux kernel sources? - </para> - </question> - <answer> - <para> - Refer to the "<link linkend='working-with-your-own-sources'>Working With Your Own Sources</link>" - section for information. - </para> - </answer> - </qandaentry> - - <qandaentry> - <question> - <para> - How do I install/not-install the kernel image on the rootfs? - </para> - </question> - <answer> - <para> - The kernel image (e.g. <filename>vmlinuz</filename>) is provided - by the <filename>kernel-image</filename> package. - Image recipes depend on <filename>kernel-base</filename>. - To specify whether or not the kernel - image is installed in the generated root filesystem, override - <filename>RDEPENDS_kernel-base</filename> to include or not - include "kernel-image".</para> - <para>See the - "<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>" - section in the Yocto Project Development Tasks Manual - for information on how to use an append file to - override metadata. - </para> - </answer> - </qandaentry> - - <qandaentry> - <question> - <para> - How do I install a specific kernel module? - </para> - </question> - <answer> - <para> - Linux kernel modules are packaged individually. - To ensure a specific kernel module is included in an image, - include it in the appropriate machine - <ulink url='&YOCTO_DOCS_REF_URL;#var-RRECOMMENDS'><filename>RRECOMMENDS</filename></ulink> - variable.</para> - <para>These other variables are useful for installing specific - modules: - <literallayout class='monospaced'> - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RDEPENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RDEPENDS</filename></ulink> - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS'><filename>MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS</filename></ulink> - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RDEPENDS'><filename>MACHINE_EXTRA_RDEPENDS</filename></ulink> - <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE_EXTRA_RRECOMMENDS'><filename>MACHINE_EXTRA_RRECOMMENDS</filename></ulink> - </literallayout> - For example, set the following in the <filename>qemux86.conf</filename> - file to include the <filename>ab123</filename> kernel modules - with images built for the <filename>qemux86</filename> machine: - <literallayout class='monospaced'> - MACHINE_EXTRA_RRECOMMENDS += "kernel-module-ab123" - </literallayout> - For more information, see the - "<link linkend='incorporating-out-of-tree-modules'>Incorporating Out-of-Tree Modules</link>" - section. - </para> - </answer> - </qandaentry> - - <qandaentry> - <question> - <para> - How do I change the Linux kernel command line? - </para> - </question> - <answer> - <para> - The Linux kernel command line is typically specified in - the machine config using the <filename>APPEND</filename> variable. - For example, you can add some helpful debug information doing - the following: - <literallayout class='monospaced'> - APPEND += "printk.time=y initcall_debug debug" - </literallayout> - </para> - </answer> - </qandaentry> - </qandaset> - </para> -</section> -</appendix> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-intro.xml b/documentation/kernel-dev/kernel-dev-intro.xml deleted file mode 100644 index 7c1ea0e510..0000000000 --- a/documentation/kernel-dev/kernel-dev-intro.xml +++ /dev/null @@ -1,260 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<chapter id='kernel-dev-intro'> -<title>Introduction</title> - -<section id='kernel-dev-overview'> - <title>Overview</title> - - <para> - Regardless of how you intend to make use of the Yocto Project, - chances are you will work with the Linux kernel. - This manual describes how to set up your build host to support - kernel development, introduces the kernel development process, - provides background information on the Yocto Linux kernel - <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink>, - describes common tasks you can perform using the kernel tools, - shows you how to use the kernel Metadata needed to work with - the kernel inside the Yocto Project, and provides insight into how - the Yocto Project team develops and maintains Yocto Linux kernel - Git repositories and Metadata. - </para> - - <para> - Each Yocto Project release has a set of Yocto Linux kernel recipes, - whose Git repositories you can view in the Yocto - <ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink> under - the "Yocto Linux Kernel" heading. - New recipes for the release track the latest Linux kernel - upstream developments from - <ulink url='http://www.kernel.org'></ulink> and introduce - newly-supported platforms. - Previous recipes in the release are refreshed and supported for at - least one additional Yocto Project release. - As they align, these previous releases are updated to include the - latest from the Long Term Support Initiative (LTSI) project. - You can learn more about Yocto Linux kernels and LTSI in the - "<link linkend='kernel-big-picture'>Yocto Project Kernel Development and Maintenance</link>" - section. - </para> - - <para> - Also included is a Yocto Linux kernel development recipe - (<filename>linux-yocto-dev.bb</filename>) should you want to work - with the very latest in upstream Yocto Linux kernel development and - kernel Metadata development. - <note> - For more on Yocto Linux kernels, see the - "<link linkend='kernel-big-picture'>Yocto Project Kernel Development and Maintenance</link> - section. - </note> - </para> - - <para> - The Yocto Project also provides a powerful set of kernel - tools for managing Yocto Linux kernel sources and configuration data. - You can use these tools to make a single configuration change, - apply multiple patches, or work with your own kernel sources. - </para> - - <para> - In particular, the kernel tools allow you to generate configuration - fragments that specify only what you must, and nothing more. - Configuration fragments only need to contain the highest level - visible <filename>CONFIG</filename> options as presented by the - Yocto Linux kernel <filename>menuconfig</filename> system. - Contrast this against a complete Yocto Linux kernel - <filename>.config</filename> file, which includes all the automatically - selected <filename>CONFIG</filename> options. - This efficiency reduces your maintenance effort and allows you - to further separate your configuration in ways that make sense for - your project. - A common split separates policy and hardware. - For example, all your kernels might support the - <filename>proc</filename> and <filename>sys</filename> filesystems, - but only specific boards require sound, USB, or specific drivers. - Specifying these configurations individually allows you to aggregate - them together as needed, but maintains them in only one place. - Similar logic applies to separating source changes. - </para> - - <para> - If you do not maintain your own kernel sources and need to make - only minimal changes to the sources, the released recipes provide a - vetted base upon which to layer your changes. - Doing so allows you to benefit from the continual kernel - integration and testing performed during development of the - Yocto Project. - </para> - - <para> - If, instead, you have a very specific Linux kernel source tree - and are unable to align with one of the official Yocto Linux kernel - recipes, an alternative exists by which you can use the Yocto - Project Linux kernel tools with your own kernel sources. - </para> - - <para> - The remainder of this manual provides instructions for completing - specific Linux kernel development tasks. - These instructions assume you are comfortable working with - <ulink url='http://openembedded.org/wiki/Bitbake'>BitBake</ulink> - recipes and basic open-source development tools. - Understanding these concepts will facilitate the process of working - with the kernel recipes. - If you find you need some additional background, please be sure to - review and understand the following documentation: - <itemizedlist> - <listitem><para> - <ulink url='&YOCTO_DOCS_BRIEF_URL;'>Yocto Project Quick Build</ulink> - document. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_OM_URL;'>Yocto Project Overview and Concepts Manual</ulink>. - </para></listitem> - <listitem><para> - <ulink url='&YOCTO_DOCS_SDK_URL;#using-devtool-in-your-sdk-workflow'><filename>devtool</filename> workflow</ulink> - as described in the Yocto Project Application Development and - the Extensible Software Development Kit (eSDK) manual. - </para></listitem> - <listitem><para> - The - "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>" - section in the Yocto Project Development Tasks Manual. - </para></listitem> - <listitem><para> - The - "<link linkend='kernel-modification-workflow'>Kernel Modification Workflow</link>" - section. - </para></listitem> - </itemizedlist> - </para> -</section> - -<section id='kernel-modification-workflow'> - <title>Kernel Modification Workflow</title> - - <para> - Kernel modification involves changing the Yocto Project kernel, - which could involve changing configuration options as well as adding - new kernel recipes. - Configuration changes can be added in the form of configuration - fragments, while recipe modification comes through the kernel's - <filename>recipes-kernel</filename> area in a kernel layer you create. - </para> - - <para> - This section presents a high-level overview of the Yocto Project - kernel modification workflow. - The illustration and accompanying list provide general information - and references for further information. - <imagedata fileref="figures/kernel-dev-flow.png" - width="9in" depth="5in" align="center" scalefit="1" /> - </para> - - <para> - <orderedlist> - <listitem><para> - - - <emphasis>Set up Your Host Development System to Support - Development Using the Yocto Project</emphasis>: - See the - "<ulink url='&YOCTO_DOCS_DEV_URL;#dev-manual-start'>Setting Up the Development Host to Use the Yocto Project</ulink>" - section in the Yocto Project Development Tasks Manual for - options on how to get a build host ready to use the Yocto - Project. - </para></listitem> - <listitem><para> - <emphasis>Set Up Your Host Development System for Kernel Development:</emphasis> - It is recommended that you use <filename>devtool</filename> - and an extensible SDK for kernel development. - Alternatively, you can use traditional kernel development - methods with the Yocto Project. - Either way, there are steps you need to take to get the - development environment ready.</para> - - <para>Using <filename>devtool</filename> and the eSDK requires - that you have a clean build of the image and that you are - set up with the appropriate eSDK. - For more information, see the - "<link linkend='getting-ready-to-develop-using-devtool'>Getting Ready to Develop Using <filename>devtool</filename></link>" - section.</para> - - <para>Using traditional kernel development requires that you - have the kernel source available in an isolated local Git - repository. - For more information, see the - "<link linkend='getting-ready-for-traditional-kernel-development'>Getting Ready for Traditional Kernel Development</link>" - section. - </para></listitem> - <listitem><para> - <emphasis>Make Changes to the Kernel Source Code if - applicable:</emphasis> - Modifying the kernel does not always mean directly - changing source files. - However, if you have to do this, you make the changes to the - files in the eSDK's Build Directory if you are using - <filename>devtool</filename>. - For more information, see the - "<link linkend='using-devtool-to-patch-the-kernel'>Using <filename>devtool</filename> to Patch the Kernel</link>" - section.</para> - - <para>If you are using traditional kernel development, you - edit the source files in the kernel's local Git repository. - For more information, see the - "<link linkend='using-traditional-kernel-development-to-patch-the-kernel'>Using Traditional Kernel Development to Patch the Kernel</link>" - section. - </para></listitem> - <listitem><para> - <emphasis>Make Kernel Configuration Changes if - Applicable:</emphasis> - If your situation calls for changing the kernel's - configuration, you can use - <link linkend='using-menuconfig'><filename>menuconfig</filename></link>, - which allows you to interactively develop and test the - configuration changes you are making to the kernel. - Saving changes you make with <filename>menuconfig</filename> - updates the kernel's <filename>.config</filename> file. - <note><title>Warning</title> - Try to resist the temptation to directly edit an - existing <filename>.config</filename> file, which is - found in the Build Directory among the source code - used for the build. - Doing so, can produce unexpected results when the - OpenEmbedded build system regenerates the configuration - file. - </note> - Once you are satisfied with the configuration - changes made using <filename>menuconfig</filename> - and you have saved them, you can directly compare the - resulting <filename>.config</filename> file against an - existing original and gather those changes into a - <link linkend='creating-config-fragments'>configuration fragment file</link> - to be referenced from within the kernel's - <filename>.bbappend</filename> file.</para> - - <para>Additionally, if you are working in a BSP layer - and need to modify the BSP's kernel's configuration, - you can use <filename>menuconfig</filename>. - </para></listitem> - <listitem><para> - <emphasis>Rebuild the Kernel Image With Your Changes:</emphasis> - Rebuilding the kernel image applies your changes. - Depending on your target hardware, you can verify your changes - on actual hardware or perhaps QEMU. - </para></listitem> - </orderedlist> - The remainder of this developer's guide covers common tasks typically - used during kernel development, advanced Metadata usage, and Yocto Linux - kernel maintenance concepts. - </para> -</section> - -</chapter> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-maint-appx.xml b/documentation/kernel-dev/kernel-dev-maint-appx.xml deleted file mode 100644 index 3d9c7c66fd..0000000000 --- a/documentation/kernel-dev/kernel-dev-maint-appx.xml +++ /dev/null @@ -1,357 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" -[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > -<!--SPDX-License-Identifier: CC-BY-2.0-UK--> - -<appendix id='kernel-dev-maint-appx'> -<title>Kernel Maintenance</title> - - <section id='tree-construction'> - <title>Tree Construction</title> - - <para> - This section describes construction of the Yocto Project kernel - source repositories as accomplished by the Yocto Project team to - create Yocto Linux kernel repositories. - These kernel repositories are found under the heading "Yocto Linux - Kernel" at - <ulink url='&YOCTO_GIT_URL;'>&YOCTO_GIT_URL;</ulink> - and are shipped as part of a Yocto Project release. - The team creates these repositories by compiling and executing the - set of feature descriptions for every BSP and feature in the - product. - Those feature descriptions list all necessary patches, - configurations, branches, tags, and feature divisions found in a - Yocto Linux kernel. - Thus, the Yocto Project Linux kernel repository (or tree) and - accompanying Metadata in the - <filename>yocto-kernel-cache</filename> are built. - </para> - - <para> - The existence of these repositories allow you to access and clone a - particular Yocto Project Linux kernel repository and use it to - build images based on their configurations and features. - </para> - - <para> - You can find the files used to describe all the valid features and - BSPs in the Yocto Project Linux kernel in any clone of the Yocto - Project Linux kernel source repository and - <filename>yocto-kernel-cache</filename> Git trees. - For example, the following commands clone the Yocto Project - baseline Linux kernel that branches off - <filename>linux.org</filename> version 4.12 and the - <filename>yocto-kernel-cache</filename>, which contains stores of - kernel Metadata: - <literallayout class='monospaced'> - $ git clone git://git.yoctoproject.org/linux-yocto-4.12 - $ git clone git://git.yoctoproject.org/linux-kernel-cache - </literallayout> - For more information on how to set up a local Git repository of - the Yocto Project Linux kernel files, see the - "<link linkend='preparing-the-build-host-to-work-on-the-kernel'>Preparing the Build Host to Work on the Kernel</link>" - section. - </para> - - <para> - Once you have cloned the kernel Git repository and the - cache of Metadata on your local machine, you can discover the - branches that are available in the repository using the following - Git command: - <literallayout class='monospaced'> - $ git branch -a - </literallayout> - Checking out a branch allows you to work with a particular - Yocto Linux kernel. - For example, the following commands check out the - "standard/beagleboard" branch of the Yocto Linux kernel repository - and the "yocto-4.12" branch of the - <filename>yocto-kernel-cache</filename> repository: - <literallayout class='monospaced'> - $ cd ~/linux-yocto-4.12 - $ git checkout -b my-kernel-4.12 remotes/origin/standard/beagleboard - $ cd ~/linux-kernel-cache - $ git checkout -b my-4.12-metadata remotes/origin/yocto-4.12 - </literallayout> - <note> - Branches in the <filename>yocto-kernel-cache</filename> - repository correspond to Yocto Linux kernel versions - (e.g. "yocto-4.12", "yocto-4.10", "yocto-4.9", and so forth). - </note> - Once you have checked out and switched to appropriate branches, - you can see a snapshot of all the kernel source files used to - used to build that particular Yocto Linux kernel for a - particular board. - </para> - - <para> - To see the features and configurations for a particular Yocto - Linux kernel, you need to examine the - <filename>yocto-kernel-cache</filename> Git repository. - As mentioned, branches in the - <filename>yocto-kernel-cache</filename> repository correspond to - Yocto Linux kernel versions (e.g. <filename>yocto-4.12</filename>). - Branches contain descriptions in the form of - <filename>.scc</filename> and <filename>.cfg</filename> files. - </para> - - <para> - You should realize, however, that browsing your local - <filename>yocto-kernel-cache</filename> repository for feature - descriptions and patches is not an effective way to determine what - is in a particular kernel branch. - Instead, you should use Git directly to discover the changes in - a branch. - Using Git is an efficient and flexible way to inspect changes to - the kernel. - <note> - Ground up reconstruction of the complete kernel tree is an - action only taken by the Yocto Project team during an active - development cycle. - When you create a clone of the kernel Git repository, you are - simply making it efficiently available for building and - development. - </note> - </para> - - <para> - The following steps describe what happens when the Yocto Project - Team constructs the Yocto Project kernel source Git repository - (or tree) found at - <ulink url='&YOCTO_GIT_URL;'></ulink> given the - introduction of a new top-level kernel feature or BSP. - The following actions effectively provide the Metadata - and create the tree that includes the new feature, patch, or BSP: - <orderedlist> - <listitem><para> - <emphasis>Pass Feature to the OpenEmbedded Build System:</emphasis> - A top-level kernel feature is passed to the kernel build - subsystem. - Normally, this feature is a BSP for a particular kernel - type. - </para></listitem> - <listitem><para> - <emphasis>Locate Feature:</emphasis> - The file that describes the top-level feature is located - by searching these system directories: - <itemizedlist> - <listitem><para> - The in-tree kernel-cache directories, which are - located in the - <ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/yocto-kernel-cache/tree/bsp'><filename>yocto-kernel-cache</filename></ulink> - repository organized under the "Yocto Linux Kernel" - heading in the - <ulink url='http://git.yoctoproject.org/cgit/cgit.cgi'>Yocto Project Source Repositories</ulink>. - </para></listitem> - <listitem><para> - Areas pointed to by <filename>SRC_URI</filename> - statements found in kernel recipes - </para></listitem> - </itemizedlist> - For a typical build, the target of the search is a - feature description in an <filename>.scc</filename> file - whose name follows this format (e.g. - <filename>beaglebone-standard.scc</filename> and - <filename>beaglebone-preempt-rt.scc</filename>): - <literallayout class='monospaced'> - <replaceable>bsp_root_name</replaceable>-<replaceable>kernel_type</replaceable>.scc - </literallayout> - </para></listitem> - <listitem><para> - <emphasis>Expand Feature:</emphasis> - Once located, the feature description is either expanded - into a simple script of actions, or into an existing - equivalent script that is already part of the shipped - kernel. - </para></listitem> - <listitem><para> - <emphasis>Append Extra Features:</emphasis> - Extra features are appended to the top-level feature - description. - These features can come from the - <ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink> - variable in recipes. - </para></listitem> - <listitem><para> - <emphasis>Locate, Expand, and Append Each Feature:</emphasis> - Each extra feature is located, expanded and appended to - the script as described in step three. - </para></listitem> - <listitem><para> - <emphasis>Execute the Script:</emphasis> - The script is executed to produce files - <filename>.scc</filename> and <filename>.cfg</filename> - files in appropriate directories of the - <filename>yocto-kernel-cache</filename> repository. - These files are descriptions of all the branches, tags, - patches and configurations that need to be applied to the - base Git repository to completely create the - source (build) branch for the new BSP or feature. - </para></listitem> - <listitem><para> - <emphasis>Clone Base Repository:</emphasis> - The base repository is cloned, and the actions - listed in the <filename>yocto-kernel-cache</filename> - directories are applied to the tree. - </para></listitem> - <listitem><para> - <emphasis>Perform Cleanup:</emphasis> - The Git repositories are left with the desired branches - checked out and any required branching, patching and - tagging has been performed. - </para></listitem> - </orderedlist> - </para> - - <para> - The kernel tree and cache are ready for developer consumption to - be locally cloned, configured, and built into a Yocto Project - kernel specific to some target hardware. - <note><title>Notes</title> - <itemizedlist> - <listitem><para> - The generated <filename>yocto-kernel-cache</filename> - repository adds to the kernel as shipped with the Yocto - Project release. - Any add-ons and configuration data are applied to the - end of an existing branch. - The full repository generation that is found in the - official Yocto Project kernel repositories at - <ulink url='&YOCTO_GIT_URL;'>http://git.yoctoproject.org</ulink> - is the combination of all supported boards and - configurations. - </para></listitem> - <listitem><para> - The technique the Yocto Project team uses is flexible - and allows for seamless blending of an immutable - history with additional patches specific to a - deployment. - Any additions to the kernel become an integrated part - of the branches. - </para></listitem> - <listitem><para> - The full kernel tree that you see on - <ulink url='&YOCTO_GIT_URL;'></ulink> is - generated through repeating the above steps for all - valid BSPs. - The end result is a branched, clean history tree that - makes up the kernel for a given release. - You can see the script (<filename>kgit-scc</filename>) - responsible for this in the - <ulink url='&YOCTO_GIT_URL;/cgit.cgi/yocto-kernel-tools/tree/tools'><filename>yocto-kernel-tools</filename></ulink> - repository. - </para></listitem> - <listitem><para> - The steps used to construct the full kernel tree are - the same steps that BitBake uses when it builds a - kernel image. - </para></listitem> - </itemizedlist> - </note> - </para> - </section> - - <section id='build-strategy'> - <title>Build Strategy</title> - - <para> - Once you have cloned a Yocto Linux kernel repository and the - cache repository (<filename>yocto-kernel-cache</filename>) onto - your development system, you can consider the compilation phase - of kernel development, which is building a kernel image. - Some prerequisites exist that are validated by the build process - before compilation starts: - </para> - - <itemizedlist> - <listitem><para> - The - <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> - points to the kernel Git repository. - </para></listitem> - <listitem><para> - A BSP build branch with Metadata exists in the - <filename>yocto-kernel-cache</filename> repository. - The branch is based on the Yocto Linux kernel version and - has configurations and features grouped under the - <filename>yocto-kernel-cache/bsp</filename> directory. - For example, features and configurations for the - BeagleBone Board assuming a - <filename>linux-yocto_4.12</filename> kernel reside in the - following area of the <filename>yocto-kernel-cache</filename> - repository: - <literallayout class='monospaced'> - yocto-kernel-cache/bsp/beaglebone - </literallayout> - <note> - In the previous example, the "yocto-4.12" branch is - checked out in the <filename>yocto-kernel-cache</filename> - repository. - </note> - </para></listitem> - </itemizedlist> - - <para> - The OpenEmbedded build system makes sure these conditions exist - before attempting compilation. - Other means, however, do exist, such as as bootstrapping a BSP. - </para> - - <para> - Before building a kernel, the build process verifies the tree - and configures the kernel by processing all of the - configuration "fragments" specified by feature descriptions - in the <filename>.scc</filename> files. - As the features are compiled, associated kernel configuration - fragments are noted and recorded in the series of directories - in their compilation order. - The fragments are migrated, pre-processed and passed to the - Linux Kernel Configuration subsystem (<filename>lkc</filename>) as - raw input in the form of a <filename>.config</filename> file. - The <filename>lkc</filename> uses its own internal dependency - constraints to do the final processing of that information and - generates the final <filename>.config</filename> file that is used - during compilation. - </para> - - <para> - Using the board's architecture and other relevant values from - the board's template, kernel compilation is started and a kernel - image is produced. - </para> - - <para> - The other thing that you notice once you configure a kernel is that - the build process generates a build tree that is separate from - your kernel's local Git source repository tree. - This build tree has a name that uses the following form, where - <filename>${MACHINE}</filename> is the metadata name of the - machine (BSP) and "kernel_type" is one of the Yocto Project - supported kernel types (e.g. "standard"): - <literallayout class='monospaced'> - linux-${MACHINE}-<replaceable>kernel_type</replaceable>-build - </literallayout> - </para> - - <para> - The existing support in the <filename>kernel.org</filename> tree - achieves this default functionality. - </para> - - <para> - This behavior means that all the generated files for a particular - machine or BSP are now in the build tree directory. - The files include the final <filename>.config</filename> file, - all the <filename>.o</filename> files, the <filename>.a</filename> - files, and so forth. - Since each machine or BSP has its own separate - <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink> - in its own separate branch of the Git repository, you can easily - switch between different builds. - </para> - </section> -</appendix> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-style.css b/documentation/kernel-dev/kernel-dev-style.css deleted file mode 100644 index fc6fbb8de1..0000000000 --- a/documentation/kernel-dev/kernel-dev-style.css +++ /dev/null @@ -1,991 +0,0 @@ -/* - - SPDX-License-Identifier: CC-BY-2.0-UK - - Generic XHTML / DocBook XHTML CSS Stylesheet. - - Browser wrangling and typographic design by - Oyvind Kolas / pippin@gimp.org - - Customised for Poky by - Matthew Allum / mallum@o-hand.com - - Thanks to: - Liam R. 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release of the - Yocto Project. - To be sure you have the latest version of the manual - for this release, go to the - <ulink url='&YOCTO_DOCS_URL;'>Yocto Project documentation page</ulink> - and select the manual from that site. - Manuals from the site are more up-to-date than manuals - derived from the Yocto Project released TAR files. - </para></listitem> - <listitem><para> - If you located this manual through a web search, the - version of the manual might not be the one you want - (e.g. the search might have returned a manual much - older than the Yocto Project version with which you - are working). - You can see all Yocto Project major releases by - visiting the - <ulink url='&YOCTO_WIKI_URL;/wiki/Releases'>Releases</ulink> - page. - If you need a version of this manual for a different - Yocto Project release, visit the - <ulink url='&YOCTO_DOCS_URL;'>Yocto Project documentation page</ulink> - and select the manual set by using the - "ACTIVE RELEASES DOCUMENTATION" or "DOCUMENTS ARCHIVE" - pull-down menus. - </para></listitem> - <listitem> - <para> - To report any inaccuracies or problems with this - (or any other Yocto Project) manual, send an email to - the Yocto Project documentation mailing list at - <filename>docs@lists.yoctoproject.org</filename> or - log into the freenode <filename>#yocto</filename> channel. - </para> - </listitem> - </itemizedlist> - </note> - </legalnotice> - - </bookinfo> - - <xi:include href="kernel-dev-intro.xml"/> - - <xi:include href="kernel-dev-common.xml"/> - - <xi:include href="kernel-dev-advanced.xml"/> - - <xi:include href="kernel-dev-concepts-appx.xml"/> - - <xi:include href="kernel-dev-maint-appx.xml"/> - - <xi:include href="kernel-dev-faq.xml"/> - -<!-- <index id='index'> - <title>Index</title> - </index> ---> - -</book> -<!-- -vim: expandtab tw=80 ts=4 ---> diff --git a/documentation/kernel-dev/kernel-dev-maint-appx.rst b/documentation/kernel-dev/maint-appx.rst index 5514dac876..53b7376089 100644 --- a/documentation/kernel-dev/kernel-dev-maint-appx.rst +++ b/documentation/kernel-dev/maint-appx.rst @@ -1,4 +1,4 @@ -.. SPDX-License-Identifier: CC-BY-2.0-UK +.. SPDX-License-Identifier: CC-BY-SA-2.0-UK ****************** Kernel Maintenance @@ -28,8 +28,7 @@ in the Yocto Project Linux kernel in any clone of the Yocto Project Linux kernel source repository and ``yocto-kernel-cache`` Git trees. For example, the following commands clone the Yocto Project baseline Linux kernel that branches off ``linux.org`` version 4.12 and the -``yocto-kernel-cache``, which contains stores of kernel Metadata: -:: +``yocto-kernel-cache``, which contains stores of kernel Metadata:: $ git clone git://git.yoctoproject.org/linux-yocto-4.12 $ git clone git://git.yoctoproject.org/linux-kernel-cache @@ -37,17 +36,19 @@ kernel that branches off ``linux.org`` version 4.12 and the For more information on how to set up a local Git repository of the Yocto Project Linux kernel files, see the -":ref:`kernel-dev/kernel-dev-common:preparing the build host to work on the kernel`" +":ref:`kernel-dev/common:preparing the build host to work on the kernel`" section. Once you have cloned the kernel Git repository and the cache of Metadata on your local machine, you can discover the branches that are available -in the repository using the following Git command: $ git branch -a +in the repository using the following Git command:: + + $ git branch -a + Checking out a branch allows you to work with a particular Yocto Linux kernel. For example, the following commands check out the "standard/beagleboard" branch of the Yocto Linux kernel repository and -the "yocto-4.12" branch of the ``yocto-kernel-cache`` repository: -:: +the "yocto-4.12" branch of the ``yocto-kernel-cache`` repository:: $ cd ~/linux-yocto-4.12 $ git checkout -b my-kernel-4.12 remotes/origin/standard/beagleboard @@ -56,13 +57,11 @@ the "yocto-4.12" branch of the ``yocto-kernel-cache`` repository: .. note:: - Branches in the - yocto-kernel-cache - repository correspond to Yocto Linux kernel versions (e.g. - "yocto-4.12", "yocto-4.10", "yocto-4.9", and so forth). + Branches in the ``yocto-kernel-cache`` repository correspond to Yocto Linux + kernel versions (e.g. "yocto-4.12", "yocto-4.10", "yocto-4.9", and so forth). Once you have checked out and switched to appropriate branches, you can -see a snapshot of all the kernel source files used to used to build that +see a snapshot of all the kernel source files used to build that particular Yocto Linux kernel for a particular board. To see the features and configurations for a particular Yocto Linux @@ -93,52 +92,51 @@ top-level kernel feature or BSP. The following actions effectively provide the Metadata and create the tree that includes the new feature, patch, or BSP: -1. *Pass Feature to the OpenEmbedded Build System:* A top-level kernel +#. *Pass Feature to the OpenEmbedded Build System:* A top-level kernel feature is passed to the kernel build subsystem. Normally, this feature is a BSP for a particular kernel type. -2. *Locate Feature:* The file that describes the top-level feature is +#. *Locate Feature:* The file that describes the top-level feature is located by searching these system directories: - The in-tree kernel-cache directories, which are located in the - :yocto_git:`yocto-kernel-cache </cgit/cgit.cgi/yocto-kernel-cache/tree/bsp>` + :yocto_git:`yocto-kernel-cache </yocto-kernel-cache/tree/bsp>` repository organized under the "Yocto Linux Kernel" heading in the :yocto_git:`Yocto Project Source Repositories <>`. - - Areas pointed to by ``SRC_URI`` statements found in kernel recipes + - Areas pointed to by :term:`SRC_URI` statements found in kernel recipes. For a typical build, the target of the search is a feature description in an ``.scc`` file whose name follows this format (e.g. - ``beaglebone-standard.scc`` and ``beaglebone-preempt-rt.scc``): - :: + ``beaglebone-standard.scc`` and ``beaglebone-preempt-rt.scc``):: bsp_root_name-kernel_type.scc -3. *Expand Feature:* Once located, the feature description is either +#. *Expand Feature:* Once located, the feature description is either expanded into a simple script of actions, or into an existing equivalent script that is already part of the shipped kernel. -4. *Append Extra Features:* Extra features are appended to the top-level +#. *Append Extra Features:* Extra features are appended to the top-level feature description. These features can come from the :term:`KERNEL_FEATURES` variable in recipes. -5. *Locate, Expand, and Append Each Feature:* Each extra feature is +#. *Locate, Expand, and Append Each Feature:* Each extra feature is located, expanded and appended to the script as described in step three. -6. *Execute the Script:* The script is executed to produce files +#. *Execute the Script:* The script is executed to produce files ``.scc`` and ``.cfg`` files in appropriate directories of the ``yocto-kernel-cache`` repository. These files are descriptions of all the branches, tags, patches and configurations that need to be applied to the base Git repository to completely create the source (build) branch for the new BSP or feature. -7. *Clone Base Repository:* The base repository is cloned, and the +#. *Clone Base Repository:* The base repository is cloned, and the actions listed in the ``yocto-kernel-cache`` directories are applied to the tree. -8. *Perform Cleanup:* The Git repositories are left with the desired +#. *Perform Cleanup:* The Git repositories are left with the desired branches checked out and any required branching, patching and tagging has been performed. @@ -165,7 +163,7 @@ specific to some target hardware. The end result is a branched, clean history tree that makes up the kernel for a given release. You can see the script (``kgit-scc``) responsible for this in the - :yocto_git:`yocto-kernel-tools </cgit.cgi/yocto-kernel-tools/tree/tools>` + :yocto_git:`yocto-kernel-tools </yocto-kernel-tools/tree/tools>` repository. - The steps used to construct the full kernel tree are the same @@ -177,7 +175,7 @@ Build Strategy Once you have cloned a Yocto Linux kernel repository and the cache repository (``yocto-kernel-cache``) onto your development system, you can consider the compilation phase of kernel development, which is -building a kernel image. Some prerequisites exist that are validated by +building a kernel image. Some prerequisites are validated by the build process before compilation starts: - The :term:`SRC_URI` points to the @@ -194,12 +192,10 @@ the build process before compilation starts: .. note:: In the previous example, the "yocto-4.12" branch is checked out in - the - yocto-kernel-cache - repository. + the ``yocto-kernel-cache`` repository. -The OpenEmbedded build system makes sure these conditions exist before -attempting compilation. Other means, however, do exist, such as as +The OpenEmbedded build system makes sure these conditions are satisfied before +attempting compilation. Other means, however, do exist, such as bootstrapping a BSP. Before building a kernel, the build process verifies the tree and @@ -222,8 +218,7 @@ build process generates a build tree that is separate from your kernel's local Git source repository tree. This build tree has a name that uses the following form, where ``${MACHINE}`` is the metadata name of the machine (BSP) and "kernel_type" is one of the Yocto Project supported -kernel types (e.g. "standard"): -:: +kernel types (e.g. "standard"):: linux-${MACHINE}-kernel_type-build @@ -234,6 +229,5 @@ This behavior means that all the generated files for a particular machine or BSP are now in the build tree directory. The files include the final ``.config`` file, all the ``.o`` files, the ``.a`` files, and so forth. Since each machine or BSP has its own separate -:term:`Build Directory` in its own separate -branch of the Git repository, you can easily switch between different -builds. +:term:`Build Directory` in its own separate branch of the Git repository, +you can easily switch between different builds. |