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Diffstat (limited to 'documentation/kernel-dev/advanced.rst')
| -rw-r--r-- | documentation/kernel-dev/advanced.rst | 68 |
1 files changed, 30 insertions, 38 deletions
diff --git a/documentation/kernel-dev/advanced.rst b/documentation/kernel-dev/advanced.rst index 2dbcca60c1..4c463503f6 100644 --- a/documentation/kernel-dev/advanced.rst +++ b/documentation/kernel-dev/advanced.rst @@ -69,8 +69,7 @@ to indicate the branch. 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:edgerouter = "standard/edgerouter" - + KBRANCH:beaglebone-yocto = "standard/beaglebone" The linux-yocto style recipes can optionally define the following variables: @@ -183,7 +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 @@ -304,8 +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 @@ -352,17 +351,15 @@ 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 ":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:bitbake-user-manual/bitbake-user-manual-metadata:\`\`require\`\` directive>` directive -includes the ``poky/meta/recipes-kernel/linux/linux-yocto.inc`` file, +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" @@ -566,15 +563,7 @@ 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 @@ -597,6 +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 @@ -688,12 +682,11 @@ 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, :term:`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 ":ref:`kernel-dev/common:modifying an existing recipe`" section for more information. @@ -736,11 +729,10 @@ 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 :term:`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}" +``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 @@ -764,7 +756,7 @@ 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 @@ -773,7 +765,7 @@ 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. Here are repository organization strategies maximizing source reuse, @@ -813,7 +805,7 @@ 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. |