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author | Scott Rifenbark <scott.m.rifenbark@intel.com> | 2012-12-17 17:17:14 -0600 |
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committer | Richard Purdie <richard.purdie@linuxfoundation.org> | 2013-01-16 15:59:04 +0000 |
commit | 5cbeb840061fad16524e355c07c518defae62b6e (patch) | |
tree | dccbd0db15c5ebcf8e617149080f61f2e08fe5f6 /documentation | |
parent | ea50862d40c6542d744408266aef157ce6ed5b63 (diff) | |
download | ast2050-yocto-poky-5cbeb840061fad16524e355c07c518defae62b6e.zip ast2050-yocto-poky-5cbeb840061fad16524e355c07c518defae62b6e.tar.gz |
kernel-dev: Created file structure for new kernel-dev manual.
(From yocto-docs rev: 25be3ebb7713b875c4ec6e3723961b7dd860295d)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'documentation')
-rw-r--r-- | documentation/kernel-dev/figures/kernel-dev-title.png | bin | 0 -> 27810 bytes | |||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-advanced.xml | 918 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-common.xml | 392 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-customization.xsl | 8 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-examples.xml | 918 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-faq.xml | 918 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-intro.xml | 78 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev-style.css | 979 | ||||
-rw-r--r-- | documentation/kernel-dev/kernel-dev.xml | 104 |
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diff --git a/documentation/kernel-dev/figures/kernel-dev-title.png b/documentation/kernel-dev/figures/kernel-dev-title.png Binary files differnew file mode 100644 index 0000000..1cb989f --- /dev/null +++ b/documentation/kernel-dev/figures/kernel-dev-title.png diff --git a/documentation/kernel-dev/kernel-dev-advanced.xml b/documentation/kernel-dev/kernel-dev-advanced.xml new file mode 100644 index 0000000..9d9aef6 --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-advanced.xml @@ -0,0 +1,918 @@ +<!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; ] > + +<chapter id='kernel-how-to'> + +<title>Working with the Yocto Project Kernel</title> + + +<section id='actions-org'> + <title>Introduction</title> + <para> + This chapter describes how to accomplish tasks involving a kernel's tree structure. + The information is designed to help the developer that wants to modify the Yocto + Project kernel and contribute changes upstream to the Yocto Project. + The information covers the following: + <itemizedlist> + <listitem><para>Tree construction</para></listitem> + <listitem><para>Build strategies</para></listitem> + <listitem><para>Workflow examples</para></listitem> + </itemizedlist> + </para> +</section> + + <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 kernel repositories. + These kernel repositories are found under the heading "Yocto Linux Kernel" at + <ulink url='&YOCTO_GIT_URL;/cgit.cgi'>&YOCTO_GIT_URL;/cgit.cgi</ulink> + and can be 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/feature + in the product. + Those feature descriptions list all necessary patches, + configuration, branching, tagging and feature divisions found in a kernel. + Thus, the Yocto Project kernel repository (or tree) is built. + </para> + <para> + The existence of this tree allows you to access and clone a particular + Yocto Project 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 kernel in any clone of the Yocto Project kernel source repository + Git tree. + For example, the following command clones the Yocto Project baseline kernel that + branched off of <filename>linux.org</filename> version 3.4: + <literallayout class='monospaced'> + $ git clone git://git.yoctoproject.org/linux-yocto-3.4 + </literallayout> + For another example of how to set up a local Git repository of the Yocto Project + kernel files, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink>" bulleted + item in the Yocto Project Development Manual. + </para> + <para> + Once you have cloned the kernel Git repository on your local machine, you can + switch to the <filename>meta</filename> branch within the repository. + Here is an example that assumes the local Git repository for the kernel is in + a top-level directory named <filename>linux-yocto-3.4</filename>: + <literallayout class='monospaced'> + $ cd ~/linux-yocto-3.4 + $ git checkout -b meta origin/meta + </literallayout> + Once you have checked out and switched to the <filename>meta</filename> branch, + you can see a snapshot of all the kernel configuration and feature descriptions that are + used to build that particular kernel repository. + These descriptions are in the form of <filename>.scc</filename> files. + </para> + <para> + You should realize, however, that browsing your local kernel 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. + For examples showing how to use Git to inspect kernel commits, see the following sections + in this chapter. + <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;/cgit.cgi'></ulink> given the + introduction of a new top-level kernel feature or BSP. + These are the actions that effectively create the tree + that includes the new feature, patch or BSP: + <orderedlist> + <listitem><para>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>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 <filename>meta/cfg/kernel-cache</filename></para></listitem> + <listitem><para>Areas pointed to by <filename>SRC_URI</filename> statements + found in 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: + <literallayout class='monospaced'> + <bsp_name>-<kernel_type>.scc + </literallayout> + </para></listitem> + <listitem><para>Once located, the feature description is either compiled into a simple script + of actions, or into an existing equivalent script that is already part of the + shipped kernel.</para></listitem> + <listitem><para>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>Each extra feature is located, compiled and appended to the script + as described in step three.</para></listitem> + <listitem><para>The script is executed to produce a series of <filename>meta-*</filename> + directories. + These directories 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>The base repository is cloned, and the actions + listed in the <filename>meta-*</filename> directories are applied to the + tree.</para></listitem> + <listitem><para>The Git repository is left with the desired branch checked out and any + required branching, patching and tagging has been performed.</para></listitem> + </orderedlist> + </para> + <para> + The kernel tree is now ready for developer consumption to be locally cloned, + configured, and built into a Yocto Project kernel specific to some target hardware. + <note><para>The generated <filename>meta-*</filename> directories add 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;/cgit.cgi'>http://git.yoctoproject.org/cgit.cgi</ulink> + is the combination of all supported boards and configurations.</para> + <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> + </note> + </para> + </section> + + <section id='build-strategy'> + <title>Build Strategy</title> + <para> + Once a local Git repository of the Yocto Project kernel exists on a development system, + you can consider the compilation phase of kernel development - 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 exists. + This branch has the following form: + <literallayout class='monospaced'> + <kernel_type>/<bsp_name> + </literallayout></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, see + the "<link linkend='workflow-examples'>Workflow Examples</link>". + </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 <filename>meta-*</filename> 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}-<kernel_type>-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 build directory in its own separate branch + of the Git repository, you can easily switch between different builds. + </para> + </section> + + <section id='workflow-examples'> + <title>Workflow Examples</title> + + <para> + As previously noted, the Yocto Project kernel has built-in Git integration. + However, these utilities are not the only way to work with the kernel repository. + The Yocto Project has not made changes to Git or to other tools that + would invalidate alternate workflows. + Additionally, the way the kernel repository is constructed results in using + only core Git functionality, thus allowing any number of tools or front ends to use the + resulting tree. + </para> + + <para> + This section contains several workflow examples. + Many of the examples use Git commands. + You can find Git documentation at + <ulink url='http://git-scm.com/documentation'></ulink>. + You can find a simple overview of using Git with the Yocto Project in the + "<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>" + section of the Yocto Project Development Manual. + </para> + + <section id='change-inspection-kernel-changes-commits'> + <title>Change Inspection: Changes/Commits</title> + + <para> + A common question when working with a kernel is: + "What changes have been applied to this tree?" + </para> + + <para> + In projects that have a collection of directories that + contain patches to the kernel, it is possible to inspect or "grep" the contents + of the directories to get a general feel for the changes. + This sort of patch inspection is not an efficient way to determine what has been + done to the kernel. + The reason it is inefficient is because there are many optional patches that are + selected based on the kernel type and the feature description. + Additionally, patches could exist in directories that are not included in the search. + </para> + + <para> + A more efficient way to determine what has changed in the branch is to use + Git and inspect or search the kernel tree. + This method gives you a full view of not only the source code modifications, + but also provides the reasons for the changes. + </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. + Because Git repositories in the Yocto Project do not break existing Git + functionality, and because there exists many permutations of these types of + Git commands, many methods exist by which you can discover 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='http://git.yoctoproject.org/cgit.cgi'></ulink>. + For example, the branch names for the <filename>linux-yocto-3.4</filename> + kernel repository can be seen at + <ulink url='http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads'></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 (<filename><commit>..<commit></filename>). + </para> + + <para> + Here is an example that looks at what has changed in the + <filename>emenlow</filename> branch of the + <filename>linux-yocto-3.4</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 a summary of changes use the <filename>git log</filename> command. + Here is an example using the same branches: + <literallayout class='monospaced'> + $ git log --oneline origin/standard/base..origin/standard/emenlow + </literallayout> + The <filename>git log</filename> output might be more useful than + the <filename>git whatchanged</filename> as you get + a short, one-line summary of each change and not the entire commit. + </para> + + <para> + If you want to see code differences associated with all the changes, use + the <filename>git diff</filename> command. + Here is an example: + <literallayout class='monospaced'> + $ git diff origin/standard/base..origin/standard/emenlow + </literallayout> + </para> + + <para> + You can see the commit log messages and the text differences using the + <filename>git show</filename> command: + Here is an example: + <literallayout class='monospaced'> + $ git show origin/standard/base..origin/standard/emenlow + </literallayout> + </para> + + <para> + You can create individual patches for each change by using the + <filename>git format-patch</filename> command. + 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='show-a-particular-feature-or-branch-change'> + <title>Show a Particular Feature or Branch Change</title> + + <para> + Developers use tags in the Yocto Project kernel tree to divide changes for significant + features or branches. + Once you know a particular tag, you can use Git commands + to show changes associated with the tag and find the branches that contain + the feature. + <note> + Because BSP branch, <filename>kernel.org</filename>, and feature tags are all + present, there could be many tags. + </note> + The <filename>git show <tag></filename> command shows changes that are tagged by + a feature. + Here is an example that shows changes tagged by the <filename>systemtap</filename> + feature: + <literallayout class='monospaced'> + $ git show systemtap + </literallayout> + You can use the <filename>git branch --contains <tag></filename> 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> + + <para> + You can use many other comparisons to isolate BSP and kernel changes. + For example, you can compare against <filename>kernel.org</filename> tags + such as the <filename>v3.4</filename> tag. + </para> + </section> + </section> + + <section id='development-saving-kernel-modifications'> + <title>Development: Saving Kernel Modifications</title> + + <para> + Another common operation is to build a BSP supplied by the Yocto Project, make some + changes, rebuild, and then test. + Those local changes often need to be exported, shared or otherwise maintained. + </para> + + <para> + Since the Yocto Project kernel source tree is backed by Git, this activity is + much easier as compared to with previous releases. + Because Git tracks file modifications, additions and deletions, it is easy + to modify the code and later realize that you need to save the changes. + It is also easy to determine what has changed. + This method also provides many tools to commit, undo and export those modifications. + </para> + + <para> + This section and its sub-sections, describe general application of Git's + <filename>push</filename> and <filename>pull</filename> commands, which are used to + get your changes upstream or source your code from an upstream repository. + The Yocto Project provides scripts that help you work in a collaborative development + environment. + For information on these scripts, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#pushing-a-change-upstream'>Using Scripts to Push a Change + Upstream and Request a Pull</ulink>" and + "<ulink url='&YOCTO_DOCS_DEV_URL;#submitting-a-patch'>Using Email to Submit a Patch</ulink>" + sections in the Yocto Project Development Manual. + </para> + + <para> + There are many ways to save kernel modifications. + The technique employed + depends on the destination for the patches: + + <itemizedlist> + <listitem><para>Bulk storage</para></listitem> + <listitem><para>Internal sharing either through patches or by using Git</para></listitem> + <listitem><para>External submissions</para></listitem> + <listitem><para>Exporting for integration into another Source Code + Manager (SCM)</para></listitem> + </itemizedlist> + </para> + + <para> + Because of the following list of issues, the destination of the patches also influences + the method for gathering them: + + <itemizedlist> + <listitem><para>Bisectability</para></listitem> + <listitem><para>Commit headers</para></listitem> + <listitem><para>Division of subsystems for separate submission or review</para></listitem> + </itemizedlist> + </para> + + <section id='bulk-export'> + <title>Bulk Export</title> + + <para> + This section describes how you can "bulk" export changes that have not + been separated or divided. + This situation works well when you are simply storing patches outside of the kernel + source repository, either permanently or temporarily, and you are not committing + incremental changes during development. + <note> + This technique is not appropriate for full integration of upstream submission + because changes are not properly divided and do not provide an avenue for per-change + commit messages. + Therefore, this example assumes that changes have not been committed incrementally + during development and that you simply must gather and export them. + </note> + <literallayout class='monospaced'> + # bulk export of ALL modifications without separation or division + # of the changes + + $ git add . + $ git commit -s -a -m <msg> + or + $ git commit -s -a # and interact with $EDITOR + </literallayout> + </para> + + <para> + The previous operations capture all the local changes in the project source + tree in a single Git commit. + And, that commit is also stored in the project's source tree. + </para> + + <para> + Once the changes are exported, you can restore them manually using a template + or through integration with the <filename>default_kernel</filename>. + </para> + + </section> + + <section id='incremental-planned-sharing'> + <title>Incremental/Planned Sharing</title> + + <para> + This section describes how to save modifications when you are making incremental + commits or practicing planned sharing. + The examples in this section assume that you have incrementally committed + changes to the tree during development and now need to export them. + The sections that follow + describe how you can export your changes internally through either patches or by + using Git commands. + </para> + + <para> + During development, the following commands are of interest. + For full Git documentation, refer to the Git documentation at + <ulink url='http://github.com'></ulink>. + + <literallayout class='monospaced'> + # edit a file + $ vi <path>/file + # stage the change + $ git add <path>/file + # commit the change + $ git commit -s + # remove a file + $ git rm <path>/file + # commit the change + $ git commit -s + + ... etc. + </literallayout> + </para> + + <para> + Distributed development with Git is possible when you use a universally + agreed-upon unique commit identifier (set by the creator of the commit) that maps to a + specific change set with a specific parent. + This identifier is created for you when + you create a commit, and is re-created when you amend, alter or re-apply + a commit. + As an individual in isolation, this is of no interest. + However, if you + intend to share your tree with normal Git <filename>push</filename> and + <filename>pull</filename> operations for + distributed development, you should consider the ramifications of changing a + commit that you have already shared with others. + </para> + + <para> + Assuming that the changes have not been pushed upstream, or pulled into + another repository, you can update both the commit content and commit messages + associated with development by using the following commands: + + <literallayout class='monospaced'> + $ Git add <path>/file + $ Git commit --amend + $ Git rebase or Git rebase -i + </literallayout> + </para> + + <para> + Again, assuming that the changes have not been pushed upstream, and that + no pending works-in-progress exist (use <filename>git status</filename> to check), then + you can revert (undo) commits by using the following commands: + + <literallayout class='monospaced'> + # remove the commit, update working tree and remove all + # traces of the change + $ git reset --hard HEAD^ + # remove the commit, but leave the files changed and staged for re-commit + $ git reset --soft HEAD^ + # remove the commit, leave file change, but not staged for commit + $ git reset --mixed HEAD^ + </literallayout> + </para> + + <para> + You can create branches, "cherry-pick" changes, or perform any number of Git + operations until the commits are in good order for pushing upstream + or for pull requests. + After a <filename>push</filename> or <filename>pull</filename> command, + commits are normally considered + "permanent" and you should not modify them. + If the commits need to be changed, you can incrementally do so with new commits. + These practices follow standard Git workflow and the <filename>kernel.org</filename> best + practices, which is recommended. + <note> + It is recommended to tag or branch before adding changes to a Yocto Project + BSP or before creating a new one. + The reason for this recommendation is because the branch or tag provides a + reference point to facilitate locating and exporting local changes. + </note> + </para> + + <section id='export-internally-via-patches'> + <title>Exporting Changes Internally by Using Patches</title> + + <para> + This section describes how you can extract committed changes from a working directory + by exporting them as patches. + Once the changes have been extracted, you can use the patches for upstream submission, + place them in a Yocto Project template for automatic kernel patching, + or apply them in many other common uses. + </para> + + <para> + This example shows how to create a directory with sequentially numbered patches. + Once the directory is created, you can apply it to a repository using the + <filename>git am</filename> command to reproduce the original commit and all + the related information such as author, date, commit log, and so forth. + <note> + The new commit identifiers (ID) will be generated upon re-application. + This action reflects that the commit is now applied to an underlying commit + with a different ID. + </note> + <literallayout class='monospaced'> + # <first-commit> can be a tag if one was created before development + # began. It can also be the parent branch if a branch was created + # before development began. + + $ git format-patch -o <dir> <first commit>..<last commit> + </literallayout> + </para> + + <para> + In other words: + <literallayout class='monospaced'> + # Identify commits of interest. + + # If the tree was tagged before development + $ git format-patch -o <save dir> <tag> + + # If no tags are available + $ git format-patch -o <save dir> HEAD^ # last commit + $ git format-patch -o <save dir> HEAD^^ # last 2 commits + $ git whatchanged # identify last commit + $ git format-patch -o <save dir> <commit id> + $ git format-patch -o <save dir> <rev-list> + </literallayout> + </para> + </section> + + <section id='export-internally-via-git'> + <title>Exporting Changes Internally by Using Git</title> + + <para> + This section describes how you can export changes from a working directory + by pushing the changes into a master repository or by making a pull request. + Once you have pushed the changes to the master repository, you can then + pull those same changes into a new kernel build at a later time. + </para> + + <para> + Use this command form to push the changes: + <literallayout class='monospaced'> + $ git push ssh://<master_server>/<path_to_repo> + <local_branch>:<remote_branch> + </literallayout> + </para> + + <para> + For example, the following command pushes the changes from your local branch + <filename>yocto/standard/common-pc/base</filename> to the remote branch with the same name + in the master repository <filename>//git.mycompany.com/pub/git/kernel-3.4</filename>. + <literallayout class='monospaced'> + $ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \ + yocto/standard/common-pc/base:yocto/standard/common-pc/base + </literallayout> + </para> + + <para> + A pull request entails using the <filename>git request-pull</filename> command to compose + an email to the + maintainer requesting that a branch be pulled into the master repository, see + <ulink url='http://github.com/guides/pull-requests'></ulink> for an example. + <note> + Other commands such as <filename>git stash</filename> or branching can also be used to save + changes, but are not covered in this document. + </note> + </para> + </section> + </section> + + <section id='export-for-external-upstream-submission'> + <title>Exporting Changes for External (Upstream) Submission</title> + + <para> + This section describes how to export changes for external upstream submission. + If the patch series is large or the maintainer prefers to pull + changes, you can submit these changes by using a pull request. + However, it is common to send patches as an email series. + This method allows easy review and integration of the changes. + <note> + Before sending patches for review be sure you understand the + community standards for submitting and documenting changes and follow their best practices. + For example, kernel patches should follow standards such as: + <itemizedlist> + <listitem><para> + <ulink url='http://linux.yyz.us/patch-format.html'></ulink></para></listitem> + <listitem><para>Documentation/SubmittingPatches (in any linux + kernel source tree)</para></listitem> + </itemizedlist> + </note> + </para> + + <para> + The messages used to commit changes are a large part of these standards. + Consequently, be sure that the headers for each commit have the required information. + For information on how to follow the Yocto Project commit message standards, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>How to Submit a + Change</ulink>" section in the Yocto Project Development Manual. + </para> + + <para> + If the initial commits were not properly documented or do not meet those standards, + you can re-base by using the <filename>git rebase -i</filename> command to + manipulate the commits and + get them into the required format. + Other techniques such as branching and cherry-picking commits are also viable options. + </para> + + <para> + Once you complete the commits, you can generate the email that sends the patches + to the maintainer(s) or lists that review and integrate changes. + The command <filename>git send-email</filename> is commonly used to ensure + that patches are properly + formatted for easy application and avoid mailer-induced patch damage. + </para> + + <para> + The following is an example of dumping patches for external submission: + <literallayout class='monospaced'> + # dump the last 4 commits + $ git format-patch --thread -n -o ~/rr/ HEAD^^^^ + $ git send-email --compose --subject '[RFC 0/N] <patch series summary>' \ + --to foo@yoctoproject.org --to bar@yoctoproject.org \ + --cc list@yoctoproject.org ~/rr + # the editor is invoked for the 0/N patch, and when complete the entire + # series is sent via email for review + </literallayout> + </para> + </section> + + <section id='export-for-import-into-other-scm'> + <title>Exporting Changes for Import into Another SCM</title> + + <para> + When you want to export changes for import into another + Source Code Manager (SCM), you can use any of the previously discussed + techniques. + However, if the patches are manually applied to a secondary tree and then + that tree is checked into the SCM, you can lose change information such as + commit logs. + This process is not recommended. + </para> + + <para> + Many SCMs can directly import Git commits, or can translate Git patches so that + information is not lost. + Those facilities are SCM-dependent and you should use them whenever possible. + </para> + </section> + </section> + + <section id='scm-working-with-the-yocto-project-kernel-in-another-scm'> + <title>Working with the Yocto Project Kernel in Another SCM</title> + + <para> + This section describes kernel development in an SCM other than Git, + which is not the same as exporting changes to another SCM described earlier. + For this scenario, you use the OpenEmbedded build system to + develop the kernel in a different SCM. + The following must be true for you to accomplish this: + <itemizedlist> + <listitem><para>The delivered Yocto Project kernel must be exported into the second + SCM.</para></listitem> + <listitem><para>Development must be exported from that secondary SCM into a + format that can be used by the OpenEmbedded build system.</para></listitem> + </itemizedlist> + </para> + + <section id='exporting-delivered-kernel-to-scm'> + <title>Exporting the Delivered Kernel to the SCM</title> + + <para> + Depending on the SCM, it might be possible to export the entire Yocto Project + kernel Git repository, branches and all, into a new environment. + This method is preferred because it has the most flexibility and potential to maintain + the meta data associated with each commit. + </para> + + <para> + When a direct import mechanism is not available, it is still possible to + export a branch (or series of branches) and check them into a new repository. + </para> + + <para> + The following commands illustrate some of the steps you could use to + import the <filename>yocto/standard/common-pc/base</filename> + kernel into a secondary SCM: + <literallayout class='monospaced'> + $ git checkout yocto/standard/common-pc/base + $ cd .. ; echo linux/.git > .cvsignore + $ cvs import -m "initial import" linux MY_COMPANY start + </literallayout> + </para> + + <para> + You could now relocate the CVS repository and use it in a centralized manner. + </para> + + <para> + The following commands illustrate how you can condense and merge two BSPs into a + second SCM: + <literallayout class='monospaced'> + $ git checkout yocto/standard/common-pc/base + $ git merge yocto/standard/common-pc-64/base + # resolve any conflicts and commit them + $ cd .. ; echo linux/.git > .cvsignore + $ cvs import -m "initial import" linux MY_COMPANY start + </literallayout> + </para> + </section> + + <section id='importing-changes-for-build'> + <title>Importing Changes for the Build</title> + + <para> + Once development has reached a suitable point in the second development + environment, you need to export the changes as patches. + To export them, place the changes in a recipe and + automatically apply them to the kernel during patching. + </para> + </section> + </section> + + <section id='bsp-creating'> + <title>Creating a BSP Based on an Existing Similar BSP</title> + + <para> + This section overviews the process of creating a BSP based on an + existing similar BSP. + The information is introductory in nature and does not provide step-by-step examples. + For detailed information on how to create a new BSP, see + the "<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>" section in the + Yocto Project Board Support Package (BSP) Developer's Guide, or see the + <ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>Transcript:_creating_one_generic_Atom_BSP_from_another</ulink> + wiki page. + </para> + + <para> + The basic steps you need to follow are: + <orderedlist> + <listitem><para><emphasis>Make sure you have set up a local Source Directory:</emphasis> + You must create a local + <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink> + by either creating a Git repository (recommended) or + extracting a Yocto Project release tarball.</para></listitem> + <listitem><para><emphasis>Choose an existing BSP available with the Yocto Project:</emphasis> + Try to map your board features as closely to the features of a BSP that is + already supported and exists in the Yocto Project. + Starting with something as close as possible to your board makes developing + your BSP easier. + You can find all the BSPs that are supported and ship with the Yocto Project + on the Yocto Project's Download page at + <ulink url='&YOCTO_HOME_URL;/download'></ulink>.</para></listitem> + <listitem><para><emphasis>Be sure you have the Base BSP:</emphasis> + You need to either have a local Git repository of the base BSP set up or + have downloaded and extracted the files from a release BSP tarball. + Either method gives you access to the BSP source files.</para></listitem> + <listitem><para><emphasis>Make a copy of the existing BSP, thus isolating your new + BSP work:</emphasis> + Copying the existing BSP file structure gives you a new area in which to work.</para></listitem> + <listitem><para><emphasis>Make configuration and recipe changes to your new BSP:</emphasis> + Configuration changes involve the files in the BSP's <filename>conf</filename> + directory. + Changes include creating a machine-specific configuration file and editing the + <filename>layer.conf</filename> file. + The configuration changes identify the kernel you will be using. + Recipe changes include removing, modifying, or adding new recipe files that + instruct the build process on what features to include in the image.</para></listitem> + <listitem><para><emphasis>Prepare for the build:</emphasis> + Before you actually initiate the build, you need to set up the build environment + by sourcing the environment initialization script. + After setting up the environment, you need to make some build configuration + changes to the <filename>local.conf</filename> and <filename>bblayers.conf</filename> + files.</para></listitem> + <listitem><para><emphasis>Build the image:</emphasis> + The OpenEmbedded build system uses BitBake to create the image. + You need to decide on the type of image you are going to build (e.g. minimal, base, + core, sato, and so forth) and then start the build using the <filename>bitbake</filename> + command.</para></listitem> + </orderedlist> + </para> + </section> + + <section id='tip-dirty-string'> + <title>"-dirty" String</title> + + <para> + If kernel images are being built with "-dirty" on the end of the version + string, this simply means that modifications in the source + directory have not been committed. + <literallayout class='monospaced'> + $ git status + </literallayout> + </para> + + <para> + You can use the above Git command to report modified, removed, or added files. + You should commit those changes to the tree regardless of whether they will be saved, + exported, or used. + Once you commit the changes you need to rebuild the kernel. + </para> + + <para> + To brute force pickup and commit all such pending changes, enter the following: + <literallayout class='monospaced'> + $ git add . + $ git commit -s -a -m "getting rid of -dirty" + </literallayout> + </para> + + <para> + Next, rebuild the kernel. + </para> + </section> + </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 new file mode 100644 index 0000000..1290994 --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-common.xml @@ -0,0 +1,392 @@ +<!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; ] > + +<chapter id='kernel-concepts'> + +<title>Yocto Project Kernel Concepts</title> + +<section id='concepts-org'> + <title>Introduction</title> + <para> + This chapter provides conceptual information about the kernel: + <itemizedlist> + <listitem><para>Kernel Goals</para></listitem> + <listitem><para>Kernel Development and Maintenance Overview</para></listitem> + <listitem><para>Kernel Architecture</para></listitem> + <listitem><para>Kernel Tools</para></listitem> + </itemizedlist> + </para> +</section> + + <section id='kernel-goals'> + <title>Kernel Goals</title> + <para> + The complexity of embedded kernel design has increased dramatically. + Whether it is managing multiple implementations of a particular feature or tuning and + optimizing board specific features, both flexibility and maintainability are key concerns. + The Linux kernels available through the Yocto Project are presented with the embedded + developer's needs in mind and have evolved to assist in these key concerns. + For example, prior methods such as applying hundreds of patches to an extracted + tarball have been replaced with proven techniques that allow easy inspection, + bisection and analysis of changes. + Application of these techniques also creates a platform for performing integration and + collaboration with the thousands of upstream development projects. + </para> + <para> + With all these considerations in mind, the Yocto Project's kernel and development team + strives to attain these goals: + <itemizedlist> + <listitem><para>Allow the end user to leverage community best practices to seamlessly + manage the development, build and debug cycles.</para></listitem> + <listitem><para>Create a platform for performing integration and collaboration with the + thousands of upstream development projects that exist.</para></listitem> + <listitem><para>Provide mechanisms that support many different work flows, front-ends and + management techniques.</para></listitem> + <listitem><para>Deliver the most up-to-date kernel possible while still ensuring that + the baseline kernel is the most stable official release.</para></listitem> + <listitem><para>Include major technological features as part of the Yocto Project's + upward revision strategy.</para></listitem> + <listitem><para>Present a kernel Git repository that, similar to the upstream + <filename>kernel.org</filename> tree, + has a clear and continuous history.</para></listitem> + <listitem><para>Deliver a key set of supported kernel types, where each type is tailored + to meet a specific use (e.g. networking, consumer, devices, and so forth).</para></listitem> + <listitem><para>Employ a Git branching strategy that, from a developer's point of view, + results in a linear path from the baseline <filename>kernel.org</filename>, + through a select group of features and + ends with their BSP-specific commits.</para></listitem> + </itemizedlist> + </para> + </section> + + <section id='kernel-big-picture'> + <title>Yocto Project Kernel Development and Maintenance Overview</title> + <para> + Kernels available through the Yocto Project, like other kernels, are based off the Linux + kernel releases from <ulink url='http://www.kernel.org'></ulink>. + At the beginning of a major development cycle, the Yocto Project team + chooses its 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 kernel chosen is in the + final stages of development by the community. + In other words, the kernel is in the release + candidate or "rc" phase and not yet a 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 team to deliver the most up-to-date kernel + possible, while still ensuring that the team has a stable official release for + the baseline Linux kernel version. + </para> + <para> + The ultimate source for kernels available through the Yocto Project are released kernels + from <filename>kernel.org</filename>. + In addition to a foundational kernel from <filename>kernel.org</filename>, the + kernels available contain a mix of important new mainline + developments, non-mainline developments (when there is no alternative), + 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> + Once a 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 + kernel development, BSP support, and release timing to select the best + possible <filename>kernel.org</filename> version. + The team continually monitors 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 kernel both adds features and introduces new bugs. + These consequences are the basic properties of upstream kernel development and are + managed by the Yocto Project team's kernel strategy. + It is the Yocto Project team's policy to not back-port minor features to the released 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 kernel can easily create mismatches, incompatibilities and very + subtle errors. + </para> + <para> + These policies result in both a stable and a cutting + edge kernel that mixes forward ports of existing features and significant and critical + new functionality. + Forward porting functionality in the kernels available through the Yocto Project kernel + can be thought of as a "micro uprev." + The many “micro uprevs” produce a kernel version with a mix of + important new mainline, non-mainline, BSP developments and feature integrations. + This 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 kernels is evolving and the kernels are used in leading edge + feature and BSP development. + </para> + </section> + + <section id='kernel-architecture'> + <title>Kernel Architecture</title> + <para> + This section describes the architecture of the kernels available through the + Yocto Project and provides information + on the mechanisms used to achieve that architecture. + </para> + + <section id='architecture-overview'> + <title>Overview</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 used achieve that goal in a manner similar to the + upstream <filename>kernel.org</filename>. + </para> + <para> + You can think of a Yocto Project 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 + source code manager (SCM) Git. + For information on Git as applied to the Yocto Project, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>" section in the + Yocto Project Development Manual. + </para> + <para> + The result is that 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 kernel. + </para> + <para> + The following illustration shows the conceptual Yocto Project kernel. + </para> + <para> + <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 release) from + which the Yocto Project kernel is created. + From this point "up" 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 up the tree. + Placing these common features in the + tree this way means features don't have to be duplicated along individual branches of the + structure. + </para> + <para> + From the Yocto Project Baseline Kernel, branch points represent specific functionality + for individual 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 a real-time kernel. + </para> + <para> + In this example structure, the real-time kernel branch has common features for all + real-time 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 kernel needed for any given set + of requirements. + </para> + </section> + + <section id='branching-and-workflow'> + <title>Branching Strategy and Workflow</title> + <para> + 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 branching strategy results in a tree that has features organized to be specific + for particular functionality, single kernel types, or a subset of kernel types. + This strategy also 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 they 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 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. + The developer does not need to be aware of the existence of any other branches at all. + Of course, there is value in the existence of 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> + 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 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='source-code-manager-git'> + <title>Source Code Manager - Git</title> + <para> + The Source Code Manager (SCM) is Git. + This SCM is the obvious mechanism for meeting the previously mentioned goals. + Not only is it the SCM for <filename>kernel.org</filename> but, + Git continues to grow in popularity and supports many different work flows, + front-ends and management techniques. + </para> + <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_DEV_URL;#git'>Git</ulink>" + section in the Yocto Project Development Manual. + These referenced sections overview Git and describe a minimal set of + commands that allows you to be functional using Git. + <note> + 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 Master" in order to use it with the Yocto Project. + </note> + </para> + </section> + </section> + + <section id='kernel-configuration'> + <title>Kernel Configuration</title> + <para> + Kernel configuration, along with kernel features, defines how a kernel + image is built for the Yocto Project. + Through configuration settings, you can customize a Yocto Project kernel to be + specific to particular hardware. + For example, you can specify sound support or networking support. + This section describes basic concepts behind Kernel configuration within the + Yocto Project and references you to other areas for specific configuration + applications. + </para> + + <para> + Conceptually, configuration of a Yocto Project kernel occurs similarly to that needed for any + Linux kernel. + The build process for a Yocto Project kernel uses a <filename>.config</filename> file, which + is created through the Linux Kernel Configuration (LKC) tool. + You can directly set various configurations in the + <filename>.config</filename> file by using the <filename>menuconfig</filename> + tool as built by BitBake. + You can also define configurations in the file by using configuration fragments. + <note> + It is not recommended that you edit the <filename>.config</filename> file directly. + </note> + Here are some brief descriptions of the ways you can affect the + <filename>.config</filename> file: + <itemizedlist> + <listitem><para><emphasis>The <filename>menuconfig</filename> Tool:</emphasis> + One of many front-ends that allows you to define kernel configurations. + Some others are <filename>make config</filename>, + <filename>make nconfig</filename>, and <filename>make gconfig</filename>. + In the Yocto Project environment, you must use BitBake to build the + <filename>menuconfig</filename> tool before you can use it to define + configurations: + <literallayout class='monospaced'> + $ bitbake linux-yocto -c menuconfig + </literallayout> + After the tool is built, you can interact with it normally. + You can see how <filename>menuconfig</filename> is used to change a simple + kernel configuration in the + "<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>" + section of the Yocto Project Development Manual. + For general information on <filename>menuconfig</filename>, see + <ulink url='http://en.wikipedia.org/wiki/Menuconfig'></ulink>. + </para></listitem> + <listitem><para><emphasis>Configuration Fragments:</emphasis> A file with a + list of kernel options just as they would appear syntactically in the + <filename>.config</filename> file. + Configuration fragments are typically logical groupings and are assembled + by the OpenEmbedded build system to produce input used by the LKC + that ultimately generates the <filename>.config</filename> file.</para> + <para>The + <filename><ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'>KERNEL_FEATURES</ulink></filename> + variable can be used to list configuration fragments. + For further discussion on applying configuration fragments, see the + "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-filelayout-kernel'>Linux Kernel Configuration</ulink>" + section in the Yocto Project Board Support Package (BSP) Guide. + </para></listitem> + </itemizedlist> + </para> + </section> + + <section id='kernel-tools'> + <title>Kernel Tools</title> + <para> + Since most standard workflows involve moving forward with an existing tree by + continuing to add and alter the underlying baseline, the tools that manage + the Yocto Project's kernel construction are largely hidden from the developer to + present a simplified view of the kernel for ease of use. + </para> + <para> + Fundamentally, the kernel tools that manage and construct the + Yocto Project kernel accomplish the following: + <itemizedlist> + <listitem><para>Group patches into named, reusable features.</para></listitem> + <listitem><para>Allow top-down control of included features.</para></listitem> + <listitem><para>Bind kernel configurations to kernel patches and features.</para></listitem> + <listitem><para>Present a seamless Git repository that blends Yocto Project value + with the <filename>kernel.org</filename> history and development.</para></listitem> + </itemizedlist> + </para> + </section> +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> diff --git a/documentation/kernel-dev/kernel-dev-customization.xsl b/documentation/kernel-dev/kernel-dev-customization.xsl new file mode 100644 index 0000000..8eb6905 --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-customization.xsl @@ -0,0 +1,8 @@ +<?xml version='1.0'?> +<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://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl" /> + +<!-- <xsl:param name="generate.toc" select="'article nop'"></xsl:param> --> + +</xsl:stylesheet> diff --git a/documentation/kernel-dev/kernel-dev-examples.xml b/documentation/kernel-dev/kernel-dev-examples.xml new file mode 100644 index 0000000..9d9aef6 --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-examples.xml @@ -0,0 +1,918 @@ +<!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; ] > + +<chapter id='kernel-how-to'> + +<title>Working with the Yocto Project Kernel</title> + + +<section id='actions-org'> + <title>Introduction</title> + <para> + This chapter describes how to accomplish tasks involving a kernel's tree structure. + The information is designed to help the developer that wants to modify the Yocto + Project kernel and contribute changes upstream to the Yocto Project. + The information covers the following: + <itemizedlist> + <listitem><para>Tree construction</para></listitem> + <listitem><para>Build strategies</para></listitem> + <listitem><para>Workflow examples</para></listitem> + </itemizedlist> + </para> +</section> + + <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 kernel repositories. + These kernel repositories are found under the heading "Yocto Linux Kernel" at + <ulink url='&YOCTO_GIT_URL;/cgit.cgi'>&YOCTO_GIT_URL;/cgit.cgi</ulink> + and can be 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/feature + in the product. + Those feature descriptions list all necessary patches, + configuration, branching, tagging and feature divisions found in a kernel. + Thus, the Yocto Project kernel repository (or tree) is built. + </para> + <para> + The existence of this tree allows you to access and clone a particular + Yocto Project 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 kernel in any clone of the Yocto Project kernel source repository + Git tree. + For example, the following command clones the Yocto Project baseline kernel that + branched off of <filename>linux.org</filename> version 3.4: + <literallayout class='monospaced'> + $ git clone git://git.yoctoproject.org/linux-yocto-3.4 + </literallayout> + For another example of how to set up a local Git repository of the Yocto Project + kernel files, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink>" bulleted + item in the Yocto Project Development Manual. + </para> + <para> + Once you have cloned the kernel Git repository on your local machine, you can + switch to the <filename>meta</filename> branch within the repository. + Here is an example that assumes the local Git repository for the kernel is in + a top-level directory named <filename>linux-yocto-3.4</filename>: + <literallayout class='monospaced'> + $ cd ~/linux-yocto-3.4 + $ git checkout -b meta origin/meta + </literallayout> + Once you have checked out and switched to the <filename>meta</filename> branch, + you can see a snapshot of all the kernel configuration and feature descriptions that are + used to build that particular kernel repository. + These descriptions are in the form of <filename>.scc</filename> files. + </para> + <para> + You should realize, however, that browsing your local kernel 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. + For examples showing how to use Git to inspect kernel commits, see the following sections + in this chapter. + <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;/cgit.cgi'></ulink> given the + introduction of a new top-level kernel feature or BSP. + These are the actions that effectively create the tree + that includes the new feature, patch or BSP: + <orderedlist> + <listitem><para>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>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 <filename>meta/cfg/kernel-cache</filename></para></listitem> + <listitem><para>Areas pointed to by <filename>SRC_URI</filename> statements + found in 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: + <literallayout class='monospaced'> + <bsp_name>-<kernel_type>.scc + </literallayout> + </para></listitem> + <listitem><para>Once located, the feature description is either compiled into a simple script + of actions, or into an existing equivalent script that is already part of the + shipped kernel.</para></listitem> + <listitem><para>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>Each extra feature is located, compiled and appended to the script + as described in step three.</para></listitem> + <listitem><para>The script is executed to produce a series of <filename>meta-*</filename> + directories. + These directories 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>The base repository is cloned, and the actions + listed in the <filename>meta-*</filename> directories are applied to the + tree.</para></listitem> + <listitem><para>The Git repository is left with the desired branch checked out and any + required branching, patching and tagging has been performed.</para></listitem> + </orderedlist> + </para> + <para> + The kernel tree is now ready for developer consumption to be locally cloned, + configured, and built into a Yocto Project kernel specific to some target hardware. + <note><para>The generated <filename>meta-*</filename> directories add 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;/cgit.cgi'>http://git.yoctoproject.org/cgit.cgi</ulink> + is the combination of all supported boards and configurations.</para> + <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> + </note> + </para> + </section> + + <section id='build-strategy'> + <title>Build Strategy</title> + <para> + Once a local Git repository of the Yocto Project kernel exists on a development system, + you can consider the compilation phase of kernel development - 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 exists. + This branch has the following form: + <literallayout class='monospaced'> + <kernel_type>/<bsp_name> + </literallayout></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, see + the "<link linkend='workflow-examples'>Workflow Examples</link>". + </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 <filename>meta-*</filename> 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}-<kernel_type>-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 build directory in its own separate branch + of the Git repository, you can easily switch between different builds. + </para> + </section> + + <section id='workflow-examples'> + <title>Workflow Examples</title> + + <para> + As previously noted, the Yocto Project kernel has built-in Git integration. + However, these utilities are not the only way to work with the kernel repository. + The Yocto Project has not made changes to Git or to other tools that + would invalidate alternate workflows. + Additionally, the way the kernel repository is constructed results in using + only core Git functionality, thus allowing any number of tools or front ends to use the + resulting tree. + </para> + + <para> + This section contains several workflow examples. + Many of the examples use Git commands. + You can find Git documentation at + <ulink url='http://git-scm.com/documentation'></ulink>. + You can find a simple overview of using Git with the Yocto Project in the + "<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>" + section of the Yocto Project Development Manual. + </para> + + <section id='change-inspection-kernel-changes-commits'> + <title>Change Inspection: Changes/Commits</title> + + <para> + A common question when working with a kernel is: + "What changes have been applied to this tree?" + </para> + + <para> + In projects that have a collection of directories that + contain patches to the kernel, it is possible to inspect or "grep" the contents + of the directories to get a general feel for the changes. + This sort of patch inspection is not an efficient way to determine what has been + done to the kernel. + The reason it is inefficient is because there are many optional patches that are + selected based on the kernel type and the feature description. + Additionally, patches could exist in directories that are not included in the search. + </para> + + <para> + A more efficient way to determine what has changed in the branch is to use + Git and inspect or search the kernel tree. + This method gives you a full view of not only the source code modifications, + but also provides the reasons for the changes. + </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. + Because Git repositories in the Yocto Project do not break existing Git + functionality, and because there exists many permutations of these types of + Git commands, many methods exist by which you can discover 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='http://git.yoctoproject.org/cgit.cgi'></ulink>. + For example, the branch names for the <filename>linux-yocto-3.4</filename> + kernel repository can be seen at + <ulink url='http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads'></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 (<filename><commit>..<commit></filename>). + </para> + + <para> + Here is an example that looks at what has changed in the + <filename>emenlow</filename> branch of the + <filename>linux-yocto-3.4</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 a summary of changes use the <filename>git log</filename> command. + Here is an example using the same branches: + <literallayout class='monospaced'> + $ git log --oneline origin/standard/base..origin/standard/emenlow + </literallayout> + The <filename>git log</filename> output might be more useful than + the <filename>git whatchanged</filename> as you get + a short, one-line summary of each change and not the entire commit. + </para> + + <para> + If you want to see code differences associated with all the changes, use + the <filename>git diff</filename> command. + Here is an example: + <literallayout class='monospaced'> + $ git diff origin/standard/base..origin/standard/emenlow + </literallayout> + </para> + + <para> + You can see the commit log messages and the text differences using the + <filename>git show</filename> command: + Here is an example: + <literallayout class='monospaced'> + $ git show origin/standard/base..origin/standard/emenlow + </literallayout> + </para> + + <para> + You can create individual patches for each change by using the + <filename>git format-patch</filename> command. + 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='show-a-particular-feature-or-branch-change'> + <title>Show a Particular Feature or Branch Change</title> + + <para> + Developers use tags in the Yocto Project kernel tree to divide changes for significant + features or branches. + Once you know a particular tag, you can use Git commands + to show changes associated with the tag and find the branches that contain + the feature. + <note> + Because BSP branch, <filename>kernel.org</filename>, and feature tags are all + present, there could be many tags. + </note> + The <filename>git show <tag></filename> command shows changes that are tagged by + a feature. + Here is an example that shows changes tagged by the <filename>systemtap</filename> + feature: + <literallayout class='monospaced'> + $ git show systemtap + </literallayout> + You can use the <filename>git branch --contains <tag></filename> 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> + + <para> + You can use many other comparisons to isolate BSP and kernel changes. + For example, you can compare against <filename>kernel.org</filename> tags + such as the <filename>v3.4</filename> tag. + </para> + </section> + </section> + + <section id='development-saving-kernel-modifications'> + <title>Development: Saving Kernel Modifications</title> + + <para> + Another common operation is to build a BSP supplied by the Yocto Project, make some + changes, rebuild, and then test. + Those local changes often need to be exported, shared or otherwise maintained. + </para> + + <para> + Since the Yocto Project kernel source tree is backed by Git, this activity is + much easier as compared to with previous releases. + Because Git tracks file modifications, additions and deletions, it is easy + to modify the code and later realize that you need to save the changes. + It is also easy to determine what has changed. + This method also provides many tools to commit, undo and export those modifications. + </para> + + <para> + This section and its sub-sections, describe general application of Git's + <filename>push</filename> and <filename>pull</filename> commands, which are used to + get your changes upstream or source your code from an upstream repository. + The Yocto Project provides scripts that help you work in a collaborative development + environment. + For information on these scripts, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#pushing-a-change-upstream'>Using Scripts to Push a Change + Upstream and Request a Pull</ulink>" and + "<ulink url='&YOCTO_DOCS_DEV_URL;#submitting-a-patch'>Using Email to Submit a Patch</ulink>" + sections in the Yocto Project Development Manual. + </para> + + <para> + There are many ways to save kernel modifications. + The technique employed + depends on the destination for the patches: + + <itemizedlist> + <listitem><para>Bulk storage</para></listitem> + <listitem><para>Internal sharing either through patches or by using Git</para></listitem> + <listitem><para>External submissions</para></listitem> + <listitem><para>Exporting for integration into another Source Code + Manager (SCM)</para></listitem> + </itemizedlist> + </para> + + <para> + Because of the following list of issues, the destination of the patches also influences + the method for gathering them: + + <itemizedlist> + <listitem><para>Bisectability</para></listitem> + <listitem><para>Commit headers</para></listitem> + <listitem><para>Division of subsystems for separate submission or review</para></listitem> + </itemizedlist> + </para> + + <section id='bulk-export'> + <title>Bulk Export</title> + + <para> + This section describes how you can "bulk" export changes that have not + been separated or divided. + This situation works well when you are simply storing patches outside of the kernel + source repository, either permanently or temporarily, and you are not committing + incremental changes during development. + <note> + This technique is not appropriate for full integration of upstream submission + because changes are not properly divided and do not provide an avenue for per-change + commit messages. + Therefore, this example assumes that changes have not been committed incrementally + during development and that you simply must gather and export them. + </note> + <literallayout class='monospaced'> + # bulk export of ALL modifications without separation or division + # of the changes + + $ git add . + $ git commit -s -a -m <msg> + or + $ git commit -s -a # and interact with $EDITOR + </literallayout> + </para> + + <para> + The previous operations capture all the local changes in the project source + tree in a single Git commit. + And, that commit is also stored in the project's source tree. + </para> + + <para> + Once the changes are exported, you can restore them manually using a template + or through integration with the <filename>default_kernel</filename>. + </para> + + </section> + + <section id='incremental-planned-sharing'> + <title>Incremental/Planned Sharing</title> + + <para> + This section describes how to save modifications when you are making incremental + commits or practicing planned sharing. + The examples in this section assume that you have incrementally committed + changes to the tree during development and now need to export them. + The sections that follow + describe how you can export your changes internally through either patches or by + using Git commands. + </para> + + <para> + During development, the following commands are of interest. + For full Git documentation, refer to the Git documentation at + <ulink url='http://github.com'></ulink>. + + <literallayout class='monospaced'> + # edit a file + $ vi <path>/file + # stage the change + $ git add <path>/file + # commit the change + $ git commit -s + # remove a file + $ git rm <path>/file + # commit the change + $ git commit -s + + ... etc. + </literallayout> + </para> + + <para> + Distributed development with Git is possible when you use a universally + agreed-upon unique commit identifier (set by the creator of the commit) that maps to a + specific change set with a specific parent. + This identifier is created for you when + you create a commit, and is re-created when you amend, alter or re-apply + a commit. + As an individual in isolation, this is of no interest. + However, if you + intend to share your tree with normal Git <filename>push</filename> and + <filename>pull</filename> operations for + distributed development, you should consider the ramifications of changing a + commit that you have already shared with others. + </para> + + <para> + Assuming that the changes have not been pushed upstream, or pulled into + another repository, you can update both the commit content and commit messages + associated with development by using the following commands: + + <literallayout class='monospaced'> + $ Git add <path>/file + $ Git commit --amend + $ Git rebase or Git rebase -i + </literallayout> + </para> + + <para> + Again, assuming that the changes have not been pushed upstream, and that + no pending works-in-progress exist (use <filename>git status</filename> to check), then + you can revert (undo) commits by using the following commands: + + <literallayout class='monospaced'> + # remove the commit, update working tree and remove all + # traces of the change + $ git reset --hard HEAD^ + # remove the commit, but leave the files changed and staged for re-commit + $ git reset --soft HEAD^ + # remove the commit, leave file change, but not staged for commit + $ git reset --mixed HEAD^ + </literallayout> + </para> + + <para> + You can create branches, "cherry-pick" changes, or perform any number of Git + operations until the commits are in good order for pushing upstream + or for pull requests. + After a <filename>push</filename> or <filename>pull</filename> command, + commits are normally considered + "permanent" and you should not modify them. + If the commits need to be changed, you can incrementally do so with new commits. + These practices follow standard Git workflow and the <filename>kernel.org</filename> best + practices, which is recommended. + <note> + It is recommended to tag or branch before adding changes to a Yocto Project + BSP or before creating a new one. + The reason for this recommendation is because the branch or tag provides a + reference point to facilitate locating and exporting local changes. + </note> + </para> + + <section id='export-internally-via-patches'> + <title>Exporting Changes Internally by Using Patches</title> + + <para> + This section describes how you can extract committed changes from a working directory + by exporting them as patches. + Once the changes have been extracted, you can use the patches for upstream submission, + place them in a Yocto Project template for automatic kernel patching, + or apply them in many other common uses. + </para> + + <para> + This example shows how to create a directory with sequentially numbered patches. + Once the directory is created, you can apply it to a repository using the + <filename>git am</filename> command to reproduce the original commit and all + the related information such as author, date, commit log, and so forth. + <note> + The new commit identifiers (ID) will be generated upon re-application. + This action reflects that the commit is now applied to an underlying commit + with a different ID. + </note> + <literallayout class='monospaced'> + # <first-commit> can be a tag if one was created before development + # began. It can also be the parent branch if a branch was created + # before development began. + + $ git format-patch -o <dir> <first commit>..<last commit> + </literallayout> + </para> + + <para> + In other words: + <literallayout class='monospaced'> + # Identify commits of interest. + + # If the tree was tagged before development + $ git format-patch -o <save dir> <tag> + + # If no tags are available + $ git format-patch -o <save dir> HEAD^ # last commit + $ git format-patch -o <save dir> HEAD^^ # last 2 commits + $ git whatchanged # identify last commit + $ git format-patch -o <save dir> <commit id> + $ git format-patch -o <save dir> <rev-list> + </literallayout> + </para> + </section> + + <section id='export-internally-via-git'> + <title>Exporting Changes Internally by Using Git</title> + + <para> + This section describes how you can export changes from a working directory + by pushing the changes into a master repository or by making a pull request. + Once you have pushed the changes to the master repository, you can then + pull those same changes into a new kernel build at a later time. + </para> + + <para> + Use this command form to push the changes: + <literallayout class='monospaced'> + $ git push ssh://<master_server>/<path_to_repo> + <local_branch>:<remote_branch> + </literallayout> + </para> + + <para> + For example, the following command pushes the changes from your local branch + <filename>yocto/standard/common-pc/base</filename> to the remote branch with the same name + in the master repository <filename>//git.mycompany.com/pub/git/kernel-3.4</filename>. + <literallayout class='monospaced'> + $ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \ + yocto/standard/common-pc/base:yocto/standard/common-pc/base + </literallayout> + </para> + + <para> + A pull request entails using the <filename>git request-pull</filename> command to compose + an email to the + maintainer requesting that a branch be pulled into the master repository, see + <ulink url='http://github.com/guides/pull-requests'></ulink> for an example. + <note> + Other commands such as <filename>git stash</filename> or branching can also be used to save + changes, but are not covered in this document. + </note> + </para> + </section> + </section> + + <section id='export-for-external-upstream-submission'> + <title>Exporting Changes for External (Upstream) Submission</title> + + <para> + This section describes how to export changes for external upstream submission. + If the patch series is large or the maintainer prefers to pull + changes, you can submit these changes by using a pull request. + However, it is common to send patches as an email series. + This method allows easy review and integration of the changes. + <note> + Before sending patches for review be sure you understand the + community standards for submitting and documenting changes and follow their best practices. + For example, kernel patches should follow standards such as: + <itemizedlist> + <listitem><para> + <ulink url='http://linux.yyz.us/patch-format.html'></ulink></para></listitem> + <listitem><para>Documentation/SubmittingPatches (in any linux + kernel source tree)</para></listitem> + </itemizedlist> + </note> + </para> + + <para> + The messages used to commit changes are a large part of these standards. + Consequently, be sure that the headers for each commit have the required information. + For information on how to follow the Yocto Project commit message standards, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>How to Submit a + Change</ulink>" section in the Yocto Project Development Manual. + </para> + + <para> + If the initial commits were not properly documented or do not meet those standards, + you can re-base by using the <filename>git rebase -i</filename> command to + manipulate the commits and + get them into the required format. + Other techniques such as branching and cherry-picking commits are also viable options. + </para> + + <para> + Once you complete the commits, you can generate the email that sends the patches + to the maintainer(s) or lists that review and integrate changes. + The command <filename>git send-email</filename> is commonly used to ensure + that patches are properly + formatted for easy application and avoid mailer-induced patch damage. + </para> + + <para> + The following is an example of dumping patches for external submission: + <literallayout class='monospaced'> + # dump the last 4 commits + $ git format-patch --thread -n -o ~/rr/ HEAD^^^^ + $ git send-email --compose --subject '[RFC 0/N] <patch series summary>' \ + --to foo@yoctoproject.org --to bar@yoctoproject.org \ + --cc list@yoctoproject.org ~/rr + # the editor is invoked for the 0/N patch, and when complete the entire + # series is sent via email for review + </literallayout> + </para> + </section> + + <section id='export-for-import-into-other-scm'> + <title>Exporting Changes for Import into Another SCM</title> + + <para> + When you want to export changes for import into another + Source Code Manager (SCM), you can use any of the previously discussed + techniques. + However, if the patches are manually applied to a secondary tree and then + that tree is checked into the SCM, you can lose change information such as + commit logs. + This process is not recommended. + </para> + + <para> + Many SCMs can directly import Git commits, or can translate Git patches so that + information is not lost. + Those facilities are SCM-dependent and you should use them whenever possible. + </para> + </section> + </section> + + <section id='scm-working-with-the-yocto-project-kernel-in-another-scm'> + <title>Working with the Yocto Project Kernel in Another SCM</title> + + <para> + This section describes kernel development in an SCM other than Git, + which is not the same as exporting changes to another SCM described earlier. + For this scenario, you use the OpenEmbedded build system to + develop the kernel in a different SCM. + The following must be true for you to accomplish this: + <itemizedlist> + <listitem><para>The delivered Yocto Project kernel must be exported into the second + SCM.</para></listitem> + <listitem><para>Development must be exported from that secondary SCM into a + format that can be used by the OpenEmbedded build system.</para></listitem> + </itemizedlist> + </para> + + <section id='exporting-delivered-kernel-to-scm'> + <title>Exporting the Delivered Kernel to the SCM</title> + + <para> + Depending on the SCM, it might be possible to export the entire Yocto Project + kernel Git repository, branches and all, into a new environment. + This method is preferred because it has the most flexibility and potential to maintain + the meta data associated with each commit. + </para> + + <para> + When a direct import mechanism is not available, it is still possible to + export a branch (or series of branches) and check them into a new repository. + </para> + + <para> + The following commands illustrate some of the steps you could use to + import the <filename>yocto/standard/common-pc/base</filename> + kernel into a secondary SCM: + <literallayout class='monospaced'> + $ git checkout yocto/standard/common-pc/base + $ cd .. ; echo linux/.git > .cvsignore + $ cvs import -m "initial import" linux MY_COMPANY start + </literallayout> + </para> + + <para> + You could now relocate the CVS repository and use it in a centralized manner. + </para> + + <para> + The following commands illustrate how you can condense and merge two BSPs into a + second SCM: + <literallayout class='monospaced'> + $ git checkout yocto/standard/common-pc/base + $ git merge yocto/standard/common-pc-64/base + # resolve any conflicts and commit them + $ cd .. ; echo linux/.git > .cvsignore + $ cvs import -m "initial import" linux MY_COMPANY start + </literallayout> + </para> + </section> + + <section id='importing-changes-for-build'> + <title>Importing Changes for the Build</title> + + <para> + Once development has reached a suitable point in the second development + environment, you need to export the changes as patches. + To export them, place the changes in a recipe and + automatically apply them to the kernel during patching. + </para> + </section> + </section> + + <section id='bsp-creating'> + <title>Creating a BSP Based on an Existing Similar BSP</title> + + <para> + This section overviews the process of creating a BSP based on an + existing similar BSP. + The information is introductory in nature and does not provide step-by-step examples. + For detailed information on how to create a new BSP, see + the "<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>" section in the + Yocto Project Board Support Package (BSP) Developer's Guide, or see the + <ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>Transcript:_creating_one_generic_Atom_BSP_from_another</ulink> + wiki page. + </para> + + <para> + The basic steps you need to follow are: + <orderedlist> + <listitem><para><emphasis>Make sure you have set up a local Source Directory:</emphasis> + You must create a local + <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink> + by either creating a Git repository (recommended) or + extracting a Yocto Project release tarball.</para></listitem> + <listitem><para><emphasis>Choose an existing BSP available with the Yocto Project:</emphasis> + Try to map your board features as closely to the features of a BSP that is + already supported and exists in the Yocto Project. + Starting with something as close as possible to your board makes developing + your BSP easier. + You can find all the BSPs that are supported and ship with the Yocto Project + on the Yocto Project's Download page at + <ulink url='&YOCTO_HOME_URL;/download'></ulink>.</para></listitem> + <listitem><para><emphasis>Be sure you have the Base BSP:</emphasis> + You need to either have a local Git repository of the base BSP set up or + have downloaded and extracted the files from a release BSP tarball. + Either method gives you access to the BSP source files.</para></listitem> + <listitem><para><emphasis>Make a copy of the existing BSP, thus isolating your new + BSP work:</emphasis> + Copying the existing BSP file structure gives you a new area in which to work.</para></listitem> + <listitem><para><emphasis>Make configuration and recipe changes to your new BSP:</emphasis> + Configuration changes involve the files in the BSP's <filename>conf</filename> + directory. + Changes include creating a machine-specific configuration file and editing the + <filename>layer.conf</filename> file. + The configuration changes identify the kernel you will be using. + Recipe changes include removing, modifying, or adding new recipe files that + instruct the build process on what features to include in the image.</para></listitem> + <listitem><para><emphasis>Prepare for the build:</emphasis> + Before you actually initiate the build, you need to set up the build environment + by sourcing the environment initialization script. + After setting up the environment, you need to make some build configuration + changes to the <filename>local.conf</filename> and <filename>bblayers.conf</filename> + files.</para></listitem> + <listitem><para><emphasis>Build the image:</emphasis> + The OpenEmbedded build system uses BitBake to create the image. + You need to decide on the type of image you are going to build (e.g. minimal, base, + core, sato, and so forth) and then start the build using the <filename>bitbake</filename> + command.</para></listitem> + </orderedlist> + </para> + </section> + + <section id='tip-dirty-string'> + <title>"-dirty" String</title> + + <para> + If kernel images are being built with "-dirty" on the end of the version + string, this simply means that modifications in the source + directory have not been committed. + <literallayout class='monospaced'> + $ git status + </literallayout> + </para> + + <para> + You can use the above Git command to report modified, removed, or added files. + You should commit those changes to the tree regardless of whether they will be saved, + exported, or used. + Once you commit the changes you need to rebuild the kernel. + </para> + + <para> + To brute force pickup and commit all such pending changes, enter the following: + <literallayout class='monospaced'> + $ git add . + $ git commit -s -a -m "getting rid of -dirty" + </literallayout> + </para> + + <para> + Next, rebuild the kernel. + </para> + </section> + </section> +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> diff --git a/documentation/kernel-dev/kernel-dev-faq.xml b/documentation/kernel-dev/kernel-dev-faq.xml new file mode 100644 index 0000000..9d9aef6 --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-faq.xml @@ -0,0 +1,918 @@ +<!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; ] > + +<chapter id='kernel-how-to'> + +<title>Working with the Yocto Project Kernel</title> + + +<section id='actions-org'> + <title>Introduction</title> + <para> + This chapter describes how to accomplish tasks involving a kernel's tree structure. + The information is designed to help the developer that wants to modify the Yocto + Project kernel and contribute changes upstream to the Yocto Project. + The information covers the following: + <itemizedlist> + <listitem><para>Tree construction</para></listitem> + <listitem><para>Build strategies</para></listitem> + <listitem><para>Workflow examples</para></listitem> + </itemizedlist> + </para> +</section> + + <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 kernel repositories. + These kernel repositories are found under the heading "Yocto Linux Kernel" at + <ulink url='&YOCTO_GIT_URL;/cgit.cgi'>&YOCTO_GIT_URL;/cgit.cgi</ulink> + and can be 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/feature + in the product. + Those feature descriptions list all necessary patches, + configuration, branching, tagging and feature divisions found in a kernel. + Thus, the Yocto Project kernel repository (or tree) is built. + </para> + <para> + The existence of this tree allows you to access and clone a particular + Yocto Project 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 kernel in any clone of the Yocto Project kernel source repository + Git tree. + For example, the following command clones the Yocto Project baseline kernel that + branched off of <filename>linux.org</filename> version 3.4: + <literallayout class='monospaced'> + $ git clone git://git.yoctoproject.org/linux-yocto-3.4 + </literallayout> + For another example of how to set up a local Git repository of the Yocto Project + kernel files, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Yocto Project Kernel</ulink>" bulleted + item in the Yocto Project Development Manual. + </para> + <para> + Once you have cloned the kernel Git repository on your local machine, you can + switch to the <filename>meta</filename> branch within the repository. + Here is an example that assumes the local Git repository for the kernel is in + a top-level directory named <filename>linux-yocto-3.4</filename>: + <literallayout class='monospaced'> + $ cd ~/linux-yocto-3.4 + $ git checkout -b meta origin/meta + </literallayout> + Once you have checked out and switched to the <filename>meta</filename> branch, + you can see a snapshot of all the kernel configuration and feature descriptions that are + used to build that particular kernel repository. + These descriptions are in the form of <filename>.scc</filename> files. + </para> + <para> + You should realize, however, that browsing your local kernel 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. + For examples showing how to use Git to inspect kernel commits, see the following sections + in this chapter. + <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;/cgit.cgi'></ulink> given the + introduction of a new top-level kernel feature or BSP. + These are the actions that effectively create the tree + that includes the new feature, patch or BSP: + <orderedlist> + <listitem><para>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>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 <filename>meta/cfg/kernel-cache</filename></para></listitem> + <listitem><para>Areas pointed to by <filename>SRC_URI</filename> statements + found in 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: + <literallayout class='monospaced'> + <bsp_name>-<kernel_type>.scc + </literallayout> + </para></listitem> + <listitem><para>Once located, the feature description is either compiled into a simple script + of actions, or into an existing equivalent script that is already part of the + shipped kernel.</para></listitem> + <listitem><para>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>Each extra feature is located, compiled and appended to the script + as described in step three.</para></listitem> + <listitem><para>The script is executed to produce a series of <filename>meta-*</filename> + directories. + These directories 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>The base repository is cloned, and the actions + listed in the <filename>meta-*</filename> directories are applied to the + tree.</para></listitem> + <listitem><para>The Git repository is left with the desired branch checked out and any + required branching, patching and tagging has been performed.</para></listitem> + </orderedlist> + </para> + <para> + The kernel tree is now ready for developer consumption to be locally cloned, + configured, and built into a Yocto Project kernel specific to some target hardware. + <note><para>The generated <filename>meta-*</filename> directories add 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;/cgit.cgi'>http://git.yoctoproject.org/cgit.cgi</ulink> + is the combination of all supported boards and configurations.</para> + <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> + </note> + </para> + </section> + + <section id='build-strategy'> + <title>Build Strategy</title> + <para> + Once a local Git repository of the Yocto Project kernel exists on a development system, + you can consider the compilation phase of kernel development - 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 exists. + This branch has the following form: + <literallayout class='monospaced'> + <kernel_type>/<bsp_name> + </literallayout></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, see + the "<link linkend='workflow-examples'>Workflow Examples</link>". + </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 <filename>meta-*</filename> 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}-<kernel_type>-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 build directory in its own separate branch + of the Git repository, you can easily switch between different builds. + </para> + </section> + + <section id='workflow-examples'> + <title>Workflow Examples</title> + + <para> + As previously noted, the Yocto Project kernel has built-in Git integration. + However, these utilities are not the only way to work with the kernel repository. + The Yocto Project has not made changes to Git or to other tools that + would invalidate alternate workflows. + Additionally, the way the kernel repository is constructed results in using + only core Git functionality, thus allowing any number of tools or front ends to use the + resulting tree. + </para> + + <para> + This section contains several workflow examples. + Many of the examples use Git commands. + You can find Git documentation at + <ulink url='http://git-scm.com/documentation'></ulink>. + You can find a simple overview of using Git with the Yocto Project in the + "<ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink>" + section of the Yocto Project Development Manual. + </para> + + <section id='change-inspection-kernel-changes-commits'> + <title>Change Inspection: Changes/Commits</title> + + <para> + A common question when working with a kernel is: + "What changes have been applied to this tree?" + </para> + + <para> + In projects that have a collection of directories that + contain patches to the kernel, it is possible to inspect or "grep" the contents + of the directories to get a general feel for the changes. + This sort of patch inspection is not an efficient way to determine what has been + done to the kernel. + The reason it is inefficient is because there are many optional patches that are + selected based on the kernel type and the feature description. + Additionally, patches could exist in directories that are not included in the search. + </para> + + <para> + A more efficient way to determine what has changed in the branch is to use + Git and inspect or search the kernel tree. + This method gives you a full view of not only the source code modifications, + but also provides the reasons for the changes. + </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. + Because Git repositories in the Yocto Project do not break existing Git + functionality, and because there exists many permutations of these types of + Git commands, many methods exist by which you can discover 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='http://git.yoctoproject.org/cgit.cgi'></ulink>. + For example, the branch names for the <filename>linux-yocto-3.4</filename> + kernel repository can be seen at + <ulink url='http://git.yoctoproject.org/cgit.cgi/linux-yocto-3.4/refs/heads'></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 (<filename><commit>..<commit></filename>). + </para> + + <para> + Here is an example that looks at what has changed in the + <filename>emenlow</filename> branch of the + <filename>linux-yocto-3.4</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 a summary of changes use the <filename>git log</filename> command. + Here is an example using the same branches: + <literallayout class='monospaced'> + $ git log --oneline origin/standard/base..origin/standard/emenlow + </literallayout> + The <filename>git log</filename> output might be more useful than + the <filename>git whatchanged</filename> as you get + a short, one-line summary of each change and not the entire commit. + </para> + + <para> + If you want to see code differences associated with all the changes, use + the <filename>git diff</filename> command. + Here is an example: + <literallayout class='monospaced'> + $ git diff origin/standard/base..origin/standard/emenlow + </literallayout> + </para> + + <para> + You can see the commit log messages and the text differences using the + <filename>git show</filename> command: + Here is an example: + <literallayout class='monospaced'> + $ git show origin/standard/base..origin/standard/emenlow + </literallayout> + </para> + + <para> + You can create individual patches for each change by using the + <filename>git format-patch</filename> command. + 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='show-a-particular-feature-or-branch-change'> + <title>Show a Particular Feature or Branch Change</title> + + <para> + Developers use tags in the Yocto Project kernel tree to divide changes for significant + features or branches. + Once you know a particular tag, you can use Git commands + to show changes associated with the tag and find the branches that contain + the feature. + <note> + Because BSP branch, <filename>kernel.org</filename>, and feature tags are all + present, there could be many tags. + </note> + The <filename>git show <tag></filename> command shows changes that are tagged by + a feature. + Here is an example that shows changes tagged by the <filename>systemtap</filename> + feature: + <literallayout class='monospaced'> + $ git show systemtap + </literallayout> + You can use the <filename>git branch --contains <tag></filename> 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> + + <para> + You can use many other comparisons to isolate BSP and kernel changes. + For example, you can compare against <filename>kernel.org</filename> tags + such as the <filename>v3.4</filename> tag. + </para> + </section> + </section> + + <section id='development-saving-kernel-modifications'> + <title>Development: Saving Kernel Modifications</title> + + <para> + Another common operation is to build a BSP supplied by the Yocto Project, make some + changes, rebuild, and then test. + Those local changes often need to be exported, shared or otherwise maintained. + </para> + + <para> + Since the Yocto Project kernel source tree is backed by Git, this activity is + much easier as compared to with previous releases. + Because Git tracks file modifications, additions and deletions, it is easy + to modify the code and later realize that you need to save the changes. + It is also easy to determine what has changed. + This method also provides many tools to commit, undo and export those modifications. + </para> + + <para> + This section and its sub-sections, describe general application of Git's + <filename>push</filename> and <filename>pull</filename> commands, which are used to + get your changes upstream or source your code from an upstream repository. + The Yocto Project provides scripts that help you work in a collaborative development + environment. + For information on these scripts, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#pushing-a-change-upstream'>Using Scripts to Push a Change + Upstream and Request a Pull</ulink>" and + "<ulink url='&YOCTO_DOCS_DEV_URL;#submitting-a-patch'>Using Email to Submit a Patch</ulink>" + sections in the Yocto Project Development Manual. + </para> + + <para> + There are many ways to save kernel modifications. + The technique employed + depends on the destination for the patches: + + <itemizedlist> + <listitem><para>Bulk storage</para></listitem> + <listitem><para>Internal sharing either through patches or by using Git</para></listitem> + <listitem><para>External submissions</para></listitem> + <listitem><para>Exporting for integration into another Source Code + Manager (SCM)</para></listitem> + </itemizedlist> + </para> + + <para> + Because of the following list of issues, the destination of the patches also influences + the method for gathering them: + + <itemizedlist> + <listitem><para>Bisectability</para></listitem> + <listitem><para>Commit headers</para></listitem> + <listitem><para>Division of subsystems for separate submission or review</para></listitem> + </itemizedlist> + </para> + + <section id='bulk-export'> + <title>Bulk Export</title> + + <para> + This section describes how you can "bulk" export changes that have not + been separated or divided. + This situation works well when you are simply storing patches outside of the kernel + source repository, either permanently or temporarily, and you are not committing + incremental changes during development. + <note> + This technique is not appropriate for full integration of upstream submission + because changes are not properly divided and do not provide an avenue for per-change + commit messages. + Therefore, this example assumes that changes have not been committed incrementally + during development and that you simply must gather and export them. + </note> + <literallayout class='monospaced'> + # bulk export of ALL modifications without separation or division + # of the changes + + $ git add . + $ git commit -s -a -m <msg> + or + $ git commit -s -a # and interact with $EDITOR + </literallayout> + </para> + + <para> + The previous operations capture all the local changes in the project source + tree in a single Git commit. + And, that commit is also stored in the project's source tree. + </para> + + <para> + Once the changes are exported, you can restore them manually using a template + or through integration with the <filename>default_kernel</filename>. + </para> + + </section> + + <section id='incremental-planned-sharing'> + <title>Incremental/Planned Sharing</title> + + <para> + This section describes how to save modifications when you are making incremental + commits or practicing planned sharing. + The examples in this section assume that you have incrementally committed + changes to the tree during development and now need to export them. + The sections that follow + describe how you can export your changes internally through either patches or by + using Git commands. + </para> + + <para> + During development, the following commands are of interest. + For full Git documentation, refer to the Git documentation at + <ulink url='http://github.com'></ulink>. + + <literallayout class='monospaced'> + # edit a file + $ vi <path>/file + # stage the change + $ git add <path>/file + # commit the change + $ git commit -s + # remove a file + $ git rm <path>/file + # commit the change + $ git commit -s + + ... etc. + </literallayout> + </para> + + <para> + Distributed development with Git is possible when you use a universally + agreed-upon unique commit identifier (set by the creator of the commit) that maps to a + specific change set with a specific parent. + This identifier is created for you when + you create a commit, and is re-created when you amend, alter or re-apply + a commit. + As an individual in isolation, this is of no interest. + However, if you + intend to share your tree with normal Git <filename>push</filename> and + <filename>pull</filename> operations for + distributed development, you should consider the ramifications of changing a + commit that you have already shared with others. + </para> + + <para> + Assuming that the changes have not been pushed upstream, or pulled into + another repository, you can update both the commit content and commit messages + associated with development by using the following commands: + + <literallayout class='monospaced'> + $ Git add <path>/file + $ Git commit --amend + $ Git rebase or Git rebase -i + </literallayout> + </para> + + <para> + Again, assuming that the changes have not been pushed upstream, and that + no pending works-in-progress exist (use <filename>git status</filename> to check), then + you can revert (undo) commits by using the following commands: + + <literallayout class='monospaced'> + # remove the commit, update working tree and remove all + # traces of the change + $ git reset --hard HEAD^ + # remove the commit, but leave the files changed and staged for re-commit + $ git reset --soft HEAD^ + # remove the commit, leave file change, but not staged for commit + $ git reset --mixed HEAD^ + </literallayout> + </para> + + <para> + You can create branches, "cherry-pick" changes, or perform any number of Git + operations until the commits are in good order for pushing upstream + or for pull requests. + After a <filename>push</filename> or <filename>pull</filename> command, + commits are normally considered + "permanent" and you should not modify them. + If the commits need to be changed, you can incrementally do so with new commits. + These practices follow standard Git workflow and the <filename>kernel.org</filename> best + practices, which is recommended. + <note> + It is recommended to tag or branch before adding changes to a Yocto Project + BSP or before creating a new one. + The reason for this recommendation is because the branch or tag provides a + reference point to facilitate locating and exporting local changes. + </note> + </para> + + <section id='export-internally-via-patches'> + <title>Exporting Changes Internally by Using Patches</title> + + <para> + This section describes how you can extract committed changes from a working directory + by exporting them as patches. + Once the changes have been extracted, you can use the patches for upstream submission, + place them in a Yocto Project template for automatic kernel patching, + or apply them in many other common uses. + </para> + + <para> + This example shows how to create a directory with sequentially numbered patches. + Once the directory is created, you can apply it to a repository using the + <filename>git am</filename> command to reproduce the original commit and all + the related information such as author, date, commit log, and so forth. + <note> + The new commit identifiers (ID) will be generated upon re-application. + This action reflects that the commit is now applied to an underlying commit + with a different ID. + </note> + <literallayout class='monospaced'> + # <first-commit> can be a tag if one was created before development + # began. It can also be the parent branch if a branch was created + # before development began. + + $ git format-patch -o <dir> <first commit>..<last commit> + </literallayout> + </para> + + <para> + In other words: + <literallayout class='monospaced'> + # Identify commits of interest. + + # If the tree was tagged before development + $ git format-patch -o <save dir> <tag> + + # If no tags are available + $ git format-patch -o <save dir> HEAD^ # last commit + $ git format-patch -o <save dir> HEAD^^ # last 2 commits + $ git whatchanged # identify last commit + $ git format-patch -o <save dir> <commit id> + $ git format-patch -o <save dir> <rev-list> + </literallayout> + </para> + </section> + + <section id='export-internally-via-git'> + <title>Exporting Changes Internally by Using Git</title> + + <para> + This section describes how you can export changes from a working directory + by pushing the changes into a master repository or by making a pull request. + Once you have pushed the changes to the master repository, you can then + pull those same changes into a new kernel build at a later time. + </para> + + <para> + Use this command form to push the changes: + <literallayout class='monospaced'> + $ git push ssh://<master_server>/<path_to_repo> + <local_branch>:<remote_branch> + </literallayout> + </para> + + <para> + For example, the following command pushes the changes from your local branch + <filename>yocto/standard/common-pc/base</filename> to the remote branch with the same name + in the master repository <filename>//git.mycompany.com/pub/git/kernel-3.4</filename>. + <literallayout class='monospaced'> + $ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \ + yocto/standard/common-pc/base:yocto/standard/common-pc/base + </literallayout> + </para> + + <para> + A pull request entails using the <filename>git request-pull</filename> command to compose + an email to the + maintainer requesting that a branch be pulled into the master repository, see + <ulink url='http://github.com/guides/pull-requests'></ulink> for an example. + <note> + Other commands such as <filename>git stash</filename> or branching can also be used to save + changes, but are not covered in this document. + </note> + </para> + </section> + </section> + + <section id='export-for-external-upstream-submission'> + <title>Exporting Changes for External (Upstream) Submission</title> + + <para> + This section describes how to export changes for external upstream submission. + If the patch series is large or the maintainer prefers to pull + changes, you can submit these changes by using a pull request. + However, it is common to send patches as an email series. + This method allows easy review and integration of the changes. + <note> + Before sending patches for review be sure you understand the + community standards for submitting and documenting changes and follow their best practices. + For example, kernel patches should follow standards such as: + <itemizedlist> + <listitem><para> + <ulink url='http://linux.yyz.us/patch-format.html'></ulink></para></listitem> + <listitem><para>Documentation/SubmittingPatches (in any linux + kernel source tree)</para></listitem> + </itemizedlist> + </note> + </para> + + <para> + The messages used to commit changes are a large part of these standards. + Consequently, be sure that the headers for each commit have the required information. + For information on how to follow the Yocto Project commit message standards, see the + "<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>How to Submit a + Change</ulink>" section in the Yocto Project Development Manual. + </para> + + <para> + If the initial commits were not properly documented or do not meet those standards, + you can re-base by using the <filename>git rebase -i</filename> command to + manipulate the commits and + get them into the required format. + Other techniques such as branching and cherry-picking commits are also viable options. + </para> + + <para> + Once you complete the commits, you can generate the email that sends the patches + to the maintainer(s) or lists that review and integrate changes. + The command <filename>git send-email</filename> is commonly used to ensure + that patches are properly + formatted for easy application and avoid mailer-induced patch damage. + </para> + + <para> + The following is an example of dumping patches for external submission: + <literallayout class='monospaced'> + # dump the last 4 commits + $ git format-patch --thread -n -o ~/rr/ HEAD^^^^ + $ git send-email --compose --subject '[RFC 0/N] <patch series summary>' \ + --to foo@yoctoproject.org --to bar@yoctoproject.org \ + --cc list@yoctoproject.org ~/rr + # the editor is invoked for the 0/N patch, and when complete the entire + # series is sent via email for review + </literallayout> + </para> + </section> + + <section id='export-for-import-into-other-scm'> + <title>Exporting Changes for Import into Another SCM</title> + + <para> + When you want to export changes for import into another + Source Code Manager (SCM), you can use any of the previously discussed + techniques. + However, if the patches are manually applied to a secondary tree and then + that tree is checked into the SCM, you can lose change information such as + commit logs. + This process is not recommended. + </para> + + <para> + Many SCMs can directly import Git commits, or can translate Git patches so that + information is not lost. + Those facilities are SCM-dependent and you should use them whenever possible. + </para> + </section> + </section> + + <section id='scm-working-with-the-yocto-project-kernel-in-another-scm'> + <title>Working with the Yocto Project Kernel in Another SCM</title> + + <para> + This section describes kernel development in an SCM other than Git, + which is not the same as exporting changes to another SCM described earlier. + For this scenario, you use the OpenEmbedded build system to + develop the kernel in a different SCM. + The following must be true for you to accomplish this: + <itemizedlist> + <listitem><para>The delivered Yocto Project kernel must be exported into the second + SCM.</para></listitem> + <listitem><para>Development must be exported from that secondary SCM into a + format that can be used by the OpenEmbedded build system.</para></listitem> + </itemizedlist> + </para> + + <section id='exporting-delivered-kernel-to-scm'> + <title>Exporting the Delivered Kernel to the SCM</title> + + <para> + Depending on the SCM, it might be possible to export the entire Yocto Project + kernel Git repository, branches and all, into a new environment. + This method is preferred because it has the most flexibility and potential to maintain + the meta data associated with each commit. + </para> + + <para> + When a direct import mechanism is not available, it is still possible to + export a branch (or series of branches) and check them into a new repository. + </para> + + <para> + The following commands illustrate some of the steps you could use to + import the <filename>yocto/standard/common-pc/base</filename> + kernel into a secondary SCM: + <literallayout class='monospaced'> + $ git checkout yocto/standard/common-pc/base + $ cd .. ; echo linux/.git > .cvsignore + $ cvs import -m "initial import" linux MY_COMPANY start + </literallayout> + </para> + + <para> + You could now relocate the CVS repository and use it in a centralized manner. + </para> + + <para> + The following commands illustrate how you can condense and merge two BSPs into a + second SCM: + <literallayout class='monospaced'> + $ git checkout yocto/standard/common-pc/base + $ git merge yocto/standard/common-pc-64/base + # resolve any conflicts and commit them + $ cd .. ; echo linux/.git > .cvsignore + $ cvs import -m "initial import" linux MY_COMPANY start + </literallayout> + </para> + </section> + + <section id='importing-changes-for-build'> + <title>Importing Changes for the Build</title> + + <para> + Once development has reached a suitable point in the second development + environment, you need to export the changes as patches. + To export them, place the changes in a recipe and + automatically apply them to the kernel during patching. + </para> + </section> + </section> + + <section id='bsp-creating'> + <title>Creating a BSP Based on an Existing Similar BSP</title> + + <para> + This section overviews the process of creating a BSP based on an + existing similar BSP. + The information is introductory in nature and does not provide step-by-step examples. + For detailed information on how to create a new BSP, see + the "<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>" section in the + Yocto Project Board Support Package (BSP) Developer's Guide, or see the + <ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>Transcript:_creating_one_generic_Atom_BSP_from_another</ulink> + wiki page. + </para> + + <para> + The basic steps you need to follow are: + <orderedlist> + <listitem><para><emphasis>Make sure you have set up a local Source Directory:</emphasis> + You must create a local + <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink> + by either creating a Git repository (recommended) or + extracting a Yocto Project release tarball.</para></listitem> + <listitem><para><emphasis>Choose an existing BSP available with the Yocto Project:</emphasis> + Try to map your board features as closely to the features of a BSP that is + already supported and exists in the Yocto Project. + Starting with something as close as possible to your board makes developing + your BSP easier. + You can find all the BSPs that are supported and ship with the Yocto Project + on the Yocto Project's Download page at + <ulink url='&YOCTO_HOME_URL;/download'></ulink>.</para></listitem> + <listitem><para><emphasis>Be sure you have the Base BSP:</emphasis> + You need to either have a local Git repository of the base BSP set up or + have downloaded and extracted the files from a release BSP tarball. + Either method gives you access to the BSP source files.</para></listitem> + <listitem><para><emphasis>Make a copy of the existing BSP, thus isolating your new + BSP work:</emphasis> + Copying the existing BSP file structure gives you a new area in which to work.</para></listitem> + <listitem><para><emphasis>Make configuration and recipe changes to your new BSP:</emphasis> + Configuration changes involve the files in the BSP's <filename>conf</filename> + directory. + Changes include creating a machine-specific configuration file and editing the + <filename>layer.conf</filename> file. + The configuration changes identify the kernel you will be using. + Recipe changes include removing, modifying, or adding new recipe files that + instruct the build process on what features to include in the image.</para></listitem> + <listitem><para><emphasis>Prepare for the build:</emphasis> + Before you actually initiate the build, you need to set up the build environment + by sourcing the environment initialization script. + After setting up the environment, you need to make some build configuration + changes to the <filename>local.conf</filename> and <filename>bblayers.conf</filename> + files.</para></listitem> + <listitem><para><emphasis>Build the image:</emphasis> + The OpenEmbedded build system uses BitBake to create the image. + You need to decide on the type of image you are going to build (e.g. minimal, base, + core, sato, and so forth) and then start the build using the <filename>bitbake</filename> + command.</para></listitem> + </orderedlist> + </para> + </section> + + <section id='tip-dirty-string'> + <title>"-dirty" String</title> + + <para> + If kernel images are being built with "-dirty" on the end of the version + string, this simply means that modifications in the source + directory have not been committed. + <literallayout class='monospaced'> + $ git status + </literallayout> + </para> + + <para> + You can use the above Git command to report modified, removed, or added files. + You should commit those changes to the tree regardless of whether they will be saved, + exported, or used. + Once you commit the changes you need to rebuild the kernel. + </para> + + <para> + To brute force pickup and commit all such pending changes, enter the following: + <literallayout class='monospaced'> + $ git add . + $ git commit -s -a -m "getting rid of -dirty" + </literallayout> + </para> + + <para> + Next, rebuild the kernel. + </para> + </section> + </section> +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> diff --git a/documentation/kernel-dev/kernel-dev-intro.xml b/documentation/kernel-dev/kernel-dev-intro.xml new file mode 100644 index 0000000..c1cc22b --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-intro.xml @@ -0,0 +1,78 @@ +<!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; ] > + +<chapter id='kernel-doc-intro'> + +<title>Yocto Project Kernel Architecture and Use Manual</title> + +<section id='kernel-intro-section'> + <title>Introduction</title> + <para> + The Yocto Project presents kernels as a fully patched, history-clean Git + repositories. + Each repository represents selected features, board support, + and configurations extensively tested by the Yocto Project. + Yocto Project kernels allow the end user to leverage community + best practices to seamlessly manage the development, build and debug cycles. + </para> + <para> + This manual describes Yocto Project kernels by providing information + on history, organization, benefits, and use. + The manual consists of two sections: + <itemizedlist> + <listitem><para><emphasis>Concepts:</emphasis> Describes concepts behind a kernel. + You will understand how a kernel is organized and why it is organized in + the way it is. You will understand the benefits of a kernel's organization + and the mechanisms used to work with the kernel and how to apply it in your + design process.</para></listitem> + <listitem><para><emphasis>Using a Kernel:</emphasis> Describes best practices + and "how-to" information + that lets you put a kernel to practical use. + Some examples are how to examine changes in a branch and how to + save kernel modifications.</para></listitem> + </itemizedlist> + </para> + + <para> + For more information on the Linux kernel, see the following links: + <itemizedlist> + <listitem><para>The Linux Foundation's guide for kernel development + process - <ulink url='http://www.linuxfoundation.org/content/1-guide-kernel-development-process'></ulink></para></listitem> + <listitem><para>A fairly encompassing guide on Linux kernel development - + <ulink url='http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/HOWTO;hb=HEAD'></ulink></para></listitem> + </itemizedlist> + </para> + + <para> + For more discussion on the Yocto Project kernel, you can see these sections + in the Yocto Project Development Manual: + <itemizedlist> + <listitem><para> + "<ulink url='&YOCTO_DOCS_DEV_URL;#kernel-overview'>Kernel Overview</ulink>"</para></listitem> + <listitem><para> + "<ulink url='&YOCTO_DOCS_DEV_URL;#kernel-modification-workflow'>Kernel Modification Workflow</ulink>" + </para></listitem> + <listitem><para> + "<ulink url='&YOCTO_DOCS_DEV_URL;#patching-the-kernel'>Patching the Kernel</ulink>"</para></listitem> + <listitem><para> + "<ulink url='&YOCTO_DOCS_DEV_URL;#configuring-the-kernel'>Configuring the Kernel</ulink>"</para></listitem> + </itemizedlist> + </para> + + <para> + For general information on the Yocto Project, visit the website at + <ulink url='&YOCTO_HOME_URL;'></ulink>. + </para> +</section> + + + + + + + +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> diff --git a/documentation/kernel-dev/kernel-dev-style.css b/documentation/kernel-dev/kernel-dev-style.css new file mode 100644 index 0000000..a90d4af --- /dev/null +++ b/documentation/kernel-dev/kernel-dev-style.css @@ -0,0 +1,979 @@ +/* + 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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+} + +.filename { + font-size: medium; + font-family: Courier, monospace; +} + + +div.navheader, div.heading{ + position: absolute; + left: 0em; + top: 0em; + width: 100%; + background-color: #cdf; + width: 100%; +} + +div.navfooter, div.footing{ + position: fixed; + left: 0em; + bottom: 0em; + background-color: #eee; + width: 100%; +} + + +div.navheader td, +div.navfooter td { + font-size: 66%; +} + +div.navheader table th { + /*font-family: Georgia, Times, serif;*/ + /*font-size: x-large;*/ + font-size: 80%; +} + +div.navheader table { + border-left: 0em; + border-right: 0em; + border-top: 0em; + width: 100%; +} + +div.navfooter table { + border-left: 0em; + border-right: 0em; + border-bottom: 0em; + width: 100%; +} + +div.navheader table td a, +div.navfooter table td a { + color: #777; + text-decoration: none; +} + +/* normal text in the footer */ +div.navfooter table td { + color: black; +} + +div.navheader table td a:visited, +div.navfooter table td a:visited { + color: #444; +} + + +/* links in header and footer */ +div.navheader table td a:hover, +div.navfooter table td a:hover { + text-decoration: underline; + background-color: transparent; + color: #33a; +} + +div.navheader hr, +div.navfooter hr { + display: none; +} + + +.qandaset tr.question td p { + margin: 0em 0em 1em 0em; + padding: 0em 0em 0em 0em; +} + +.qandaset tr.answer td p { + margin: 0em 0em 1em 0em; + padding: 0em 0em 0em 0em; +} +.answer td { + padding-bottom: 1.5em; +} + +.emphasis { + font-weight: bold; +} + + + /************* / + / decorations / +/ *************/ + +.titlepage { +} + +.part .title { +} + +.subtitle { + border: none; +} + +/* +h1 { + border: none; +} + +h2 { + border-top: solid 0.2em; + border-bottom: solid 0.06em; +} + +h3 { + border-top: 0em; + border-bottom: solid 0.06em; +} + +h4 { + border: 0em; + border-bottom: solid 0.06em; +} + +h5 { + border: 0em; +} +*/ + +.programlisting { + border: solid 1px; +} + +div.figure, +div.table, +div.informalfigure, +div.informaltable, +div.informalexample, +div.example { + border: 1px solid; +} + + + +.tip, +.warning, +.caution, +.note { + border: 1px solid; +} + +.tip table th, +.warning table th, +.caution table th, +.note table th { + border-bottom: 1px solid; +} + +.question td { + border-top: 1px solid black; +} + +.answer { +} + + +b.keycap, +.keycap { + border: 1px solid; +} + + +div.navheader, div.heading{ + border-bottom: 1px solid; +} + + +div.navfooter, div.footing{ + border-top: 1px solid; +} + + /********* / + / colors / +/ *********/ + +body { + color: #333; + background: white; +} + +a { + background: transparent; +} + +a:hover { + background-color: #dedede; +} + + +h1, +h2, +h3, +h4, +h5, +h6, +h7, +h8 { + background-color: transparent; +} + +hr { + border-color: #aaa; +} + + +.tip, .warning, .caution, .note { + border-color: #fff; +} + + +.tip table th, +.warning table th, +.caution table th, +.note table th { + border-bottom-color: #fff; +} + + +.warning { + background-color: #f0f0f2; +} + +.caution { + background-color: #f0f0f2; +} + +.tip { + background-color: #f0f0f2; +} + +.note { + background-color: #f0f0f2; +} + +.glossary dl dt, +.variablelist dl dt, +.variablelist dl dt span.term { + color: #044; +} + +div.figure, +div.table, +div.example, +div.informalfigure, +div.informaltable, +div.informalexample { + border-color: #aaa; +} + +pre.programlisting { + color: black; + background-color: #fff; + border-color: #aaa; + border-width: 2px; +} + +.guimenu, +.guilabel, +.guimenuitem { + background-color: #eee; +} + + +b.keycap, +.keycap { + background-color: #eee; + border-color: #999; +} + + +div.navheader { + border-color: black; +} + + +div.navfooter { + border-color: black; +} + + + /*********** / + / graphics / +/ ***********/ + +/* +body { + background-image: url("images/body_bg.jpg"); + background-attachment: fixed; +} + +.navheader, +.note, +.tip { + background-image: url("images/note_bg.jpg"); + background-attachment: fixed; +} + +.warning, +.caution { + background-image: url("images/warning_bg.jpg"); + background-attachment: fixed; +} + +.figure, +.informalfigure, +.example, +.informalexample, +.table, +.informaltable { + background-image: url("images/figure_bg.jpg"); + background-attachment: fixed; +} + +*/ +h1, +h2, +h3, +h4, +h5, +h6, +h7{ +} + +/* +Example of how to stick an image as part of the title. + +div.article .titlepage .title +{ + background-image: url("figures/white-on-black.png"); + background-position: center; + background-repeat: repeat-x; +} +*/ + +div.preface .titlepage .title, +div.colophon .title, +div.chapter .titlepage .title, +div.article .titlepage .title +{ +} + +div.section div.section .titlepage .title, +div.sect2 .titlepage .title { + background: none; +} + + +h1.title { + background-color: transparent; + background-image: url("figures/yocto-project-bw.png"); + background-repeat: no-repeat; + height: 256px; + text-indent: -9000px; + overflow:hidden; +} + +h2.subtitle { + background-color: transparent; + text-indent: -9000px; + overflow:hidden; + width: 0px; + display: none; +} + + /*************************************** / + / pippin.gimp.org specific alterations / +/ ***************************************/ + +/* +div.heading, div.navheader { + color: #777; + font-size: 80%; + padding: 0; + margin: 0; + text-align: left; + position: absolute; + top: 0px; + left: 0px; + width: 100%; + height: 50px; + background: url('/gfx/heading_bg.png') transparent; + background-repeat: repeat-x; + background-attachment: fixed; + border: none; +} + +div.heading a { + color: #444; +} + +div.footing, div.navfooter { + border: none; + color: #ddd; + font-size: 80%; + text-align:right; + + width: 100%; + padding-top: 10px; + position: absolute; + bottom: 0px; + left: 0px; + + background: url('/gfx/footing_bg.png') transparent; +} +*/ + + + + /****************** / + / nasty ie tweaks / +/ ******************/ + +/* +div.heading, div.navheader { + width:expression(document.body.clientWidth + "px"); +} + +div.footing, div.navfooter { + width:expression(document.body.clientWidth + "px"); + margin-left:expression("-5em"); +} +body { + padding:expression("4em 5em 0em 5em"); +} +*/ + + /**************************************** / + / mozilla vendor specific css extensions / +/ ****************************************/ +/* +div.navfooter, div.footing{ + -moz-opacity: 0.8em; +} + +div.figure, +div.table, +div.informalfigure, +div.informaltable, +div.informalexample, +div.example, +.tip, +.warning, +.caution, +.note { + -moz-border-radius: 0.5em; +} + +b.keycap, +.keycap { + -moz-border-radius: 0.3em; +} +*/ + +table tr td table tr td { + display: none; +} + + +hr { + display: none; +} + +table { + border: 0em; +} + + .photo { + float: right; + margin-left: 1.5em; + margin-bottom: 1.5em; + margin-top: 0em; + max-width: 17em; + border: 1px solid gray; + padding: 3px; + background: white; +} + .seperator { + padding-top: 2em; + clear: both; + } + + #validators { + margin-top: 5em; + text-align: right; + color: #777; + } + @media print { + body { + font-size: 8pt; + } + .noprint { + display: none; + } + } + + +.tip, +.note { + background: #f0f0f2; + color: #333; + padding: 20px; + margin: 20px; +} + +.tip h3, +.note h3 { + padding: 0em; + margin: 0em; + font-size: 2em; + font-weight: bold; + color: #333; +} + +.tip a, +.note a { + color: #333; + text-decoration: underline; +} + +.footnote { + font-size: small; + color: #333; +} + +/* Changes the announcement text */ +.tip h3, +.warning h3, +.caution h3, +.note h3 { + font-size:large; + color: #00557D; +} + diff --git a/documentation/kernel-dev/kernel-dev.xml b/documentation/kernel-dev/kernel-dev.xml new file mode 100644 index 0000000..8714c07 --- /dev/null +++ b/documentation/kernel-dev/kernel-dev.xml @@ -0,0 +1,104 @@ +<!DOCTYPE book 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; ] > + +<book id='kernel-manual' lang='en' + xmlns:xi="http://www.w3.org/2003/XInclude" + xmlns="http://docbook.org/ns/docbook" + > + <bookinfo> + + <mediaobject> + <imageobject> + <imagedata fileref='figures/kernel-title.png' + format='SVG' + align='left' scalefit='1' width='100%'/> + </imageobject> + </mediaobject> + + <title></title> + + <authorgroup> + <author> + <firstname>Bruce</firstname> <surname>Ashfield</surname> + <affiliation> + <orgname>Wind River Corporation</orgname> + </affiliation> + <email>bruce.ashfield@windriver.com</email> + </author> + </authorgroup> + + <revhistory> + <revision> + <revnumber>0.9</revnumber> + <date>24 November 2010</date> + <revremark>The initial document draft released with the Yocto Project 0.9 Release.</revremark> + </revision> + <revision> + <revnumber>1.0</revnumber> + <date>6 April 2011</date> + <revremark>Released with the Yocto Project 1.0 Release.</revremark> + </revision> + <revision> + <revnumber>1.0.1</revnumber> + <date>23 May 2011</date> + <revremark>Released with the Yocto Project 1.0.1 Release.</revremark> + </revision> + <revision> + <revnumber>1.1</revnumber> + <date>6 October 2011</date> + <revremark>Released with the Yocto Project 1.1 Release.</revremark> + </revision> + <revision> + <revnumber>1.2</revnumber> + <date>April 2012</date> + <revremark>Released with the Yocto Project 1.2 Release.</revremark> + </revision> + <revision> + <revnumber>1.3</revnumber> + <date>October 2012</date> + <revremark>Released with the Yocto Project 1.3 Release.</revremark> + </revision> + <revision> + <revnumber>1.4</revnumber> + <date>Sometime in 2013</date> + <revremark>Released with the Yocto Project 1.4 Release.</revremark> + </revision> + </revhistory> + + <copyright> + <year>©RIGHT_YEAR;</year> + <holder>Linux Foundation</holder> + </copyright> + + <legalnotice> + <para> + Permission is granted to copy, distribute and/or modify this document under + the terms of the <ulink type="http" url="http://creativecommons.org/licenses/by-sa/2.0/uk/">Creative Commons Attribution-Share Alike 2.0 UK: England & Wales</ulink> as published by Creative Commons. + </para> + <note> + Due to production processes, there could be differences between the Yocto Project + documentation bundled in the release tarball and the + <ulink url='&YOCTO_DOCS_KERNEL_URL;'>Yocto Project Kernel Architecture and Use Manual</ulink> on + the <ulink url='&YOCTO_HOME_URL;'>Yocto Project</ulink> website. + For the latest version of this manual, see the manual on the website. + </note> + </legalnotice> + + </bookinfo> + + <xi:include href="kernel-doc-intro.xml"/> + + <xi:include href="kernel-concepts.xml"/> + + <xi:include href="kernel-how-to.xml"/> + +<!-- <index id='index'> + <title>Index</title> + </index> +--> + +</book> +<!-- +vim: expandtab tw=80 ts=4 +--> |