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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 b825ae7ea5..0000000000 --- a/documentation/kernel-dev/kernel-dev-maint-appx.xml +++ /dev/null @@ -1,356 +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; ] > - -<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 ---> |