From d48af3ed2141da46ef04a329bd8d9f9ef9237f1f Mon Sep 17 00:00:00 2001 From: Scott Rifenbark Date: Tue, 26 Sep 2017 17:01:51 -0700 Subject: kernel-dev: Removed "kernel-dev-examples.xml" file. File not used. (From yocto-docs rev: 208bc193b02f4644e12c7d143d20ddafc5169907) Signed-off-by: Scott Rifenbark Signed-off-by: Richard Purdie --- documentation/kernel-dev/kernel-dev-examples.xml | 918 ----------------------- 1 file changed, 918 deletions(-) delete mode 100644 documentation/kernel-dev/kernel-dev-examples.xml (limited to 'documentation/kernel-dev/kernel-dev-examples.xml') diff --git a/documentation/kernel-dev/kernel-dev-examples.xml b/documentation/kernel-dev/kernel-dev-examples.xml deleted file mode 100644 index 15622003e5..0000000000 --- a/documentation/kernel-dev/kernel-dev-examples.xml +++ /dev/null @@ -1,918 +0,0 @@ - %poky; ] > - - - -Working with the Yocto Project Kernel - - -
- Introduction - - 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: - - Tree construction - Build strategies - Workflow examples - - -
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- Tree Construction - - 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 - &YOCTO_GIT_URL;/cgit.cgi - 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. - - - 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. - - - 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 linux.org version 3.4: - - $ git clone git://git.yoctoproject.org/linux-yocto-3.4 - - For more information on how to set up a local Git repository of the - Yocto Project kernel files, see the - "Preparing the Build Host to Work on the Kernel" - section. - - - Once you have cloned the kernel Git repository on your local machine, you can - switch to the meta branch within the repository. - Here is an example that assumes the local Git repository for the kernel is in - a top-level directory named linux-yocto-3.4: - - $ cd ~/linux-yocto-3.4 - $ git checkout -b meta origin/meta - - Once you have checked out and switched to the meta 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 .scc files. - - - 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. - - 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. - - - - The following steps describe what happens when the Yocto Project Team constructs - the Yocto Project kernel source Git repository (or tree) found at - 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: - - A top-level kernel feature is passed to the kernel build subsystem. - Normally, this feature is a BSP for a particular kernel type. - The file that describes the top-level feature is located by searching - these system directories: - - The in-tree kernel-cache directories, which are located - in meta/cfg/kernel-cache - Areas pointed to by SRC_URI statements - found in recipes - - For a typical build, the target of the search is a - feature description in an .scc file - whose name follows this format: - - <bsp_name>-<kernel_type>.scc - - - 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. - Extra features are appended to the top-level feature description. - These features can come from the - KERNEL_FEATURES - variable in recipes. - Each extra feature is located, compiled and appended to the script - as described in step three. - The script is executed to produce a series of meta-* - 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. - The base repository is cloned, and the actions - listed in the meta-* directories are applied to the - tree. - The Git repository is left with the desired branch checked out and any - required branching, patching and tagging has been performed. - - - - 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. - The generated meta-* 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 - http://git.yoctoproject.org/cgit.cgi - is the combination of all supported boards and configurations. - 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. - - -
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- Build Strategy - - 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: - - - - The - SRC_URI points - to the kernel Git repository. - A BSP build branch exists. - This branch has the following form: - - <kernel_type>/<bsp_name> - - - - - 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 "Workflow Examples". - - - - 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 .scc - files. - As the features are compiled, associated kernel configuration fragments are noted - and recorded in the meta-* series of directories in their compilation order. - The fragments are migrated, pre-processed and passed to the Linux Kernel - Configuration subsystem (lkc) as raw input in the form - of a .config file. - The lkc uses its own internal dependency constraints to do the final - processing of that information and generates the final .config file - that is used during compilation. - - - - Using the board's architecture and other relevant values from the board's template, - kernel compilation is started and a kernel image is produced. - - - - 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 - ${MACHINE} is the metadata name of the machine (BSP) and "kernel_type" is one - of the Yocto Project supported kernel types (e.g. "standard"): - - linux-${MACHINE}-<kernel_type>-build - - - - - The existing support in the kernel.org tree achieves this - default functionality. - - - - This behavior means that all the generated files for a particular machine or BSP are now in - the build tree directory. - The files include the final .config file, all the .o - files, the .a files, and so forth. - Since each machine or BSP has its own separate build directory in its own separate branch - of the Git repository, you can easily switch between different builds. - -
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- Workflow Examples - - - 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. - - - - This section contains several workflow examples. - Many of the examples use Git commands. - You can find Git documentation at - . - You can find a simple overview of using Git with the Yocto Project in the - "Git" - section of the Yocto Project Reference Manual. - - -
- Change Inspection: Changes/Commits - - - A common question when working with a kernel is: - "What changes have been applied to this tree?" - - - - 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. - - - - 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. - - -
- What Changed in a Kernel? - - - 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. - - In the following examples, unless you provide a commit range, - kernel.org history is blended with Yocto Project - kernel changes. - You can form ranges by using branch names from the kernel tree as the - upper and lower commit markers with the Git commands. - You can see the branch names through the web interface to the - Yocto Project source repositories at - . - For example, the branch names for the linux-yocto-3.4 - kernel repository can be seen at - . - - To see a full range of the changes, use the - git whatchanged command and specify a commit range - for the branch (<commit>..<commit>). - - - - Here is an example that looks at what has changed in the - emenlow branch of the - linux-yocto-3.4 kernel. - The lower commit range is the commit associated with the - standard/base branch, while - the upper commit range is the commit associated with the - standard/emenlow branch. - - $ git whatchanged origin/standard/base..origin/standard/emenlow - - - - - To see a summary of changes use the git log command. - Here is an example using the same branches: - - $ git log --oneline origin/standard/base..origin/standard/emenlow - - The git log output might be more useful than - the git whatchanged as you get - a short, one-line summary of each change and not the entire commit. - - - - If you want to see code differences associated with all the changes, use - the git diff command. - Here is an example: - - $ git diff origin/standard/base..origin/standard/emenlow - - - - - You can see the commit log messages and the text differences using the - git show command: - Here is an example: - - $ git show origin/standard/base..origin/standard/emenlow - - - - - You can create individual patches for each change by using the - git format-patch command. - Here is an example that that creates patch files for each commit and - places them in your Documents directory: - - $ git format-patch -o $HOME/Documents origin/standard/base..origin/standard/emenlow - - -
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- Show a Particular Feature or Branch Change - - - 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. - - Because BSP branch, kernel.org, and feature tags are all - present, there could be many tags. - - The git show <tag> command shows changes that are tagged by - a feature. - Here is an example that shows changes tagged by the systemtap - feature: - - $ git show systemtap - - You can use the git branch --contains <tag> command - to show the branches that contain a particular feature. - This command shows the branches that contain the systemtap - feature: - - $ git branch --contains systemtap - - - - - You can use many other comparisons to isolate BSP and kernel changes. - For example, you can compare against kernel.org tags - such as the v3.4 tag. - -
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- Development: Saving Kernel Modifications - - - 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. - - - - 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. - - - - This section and its sub-sections, describe general application of Git's - push and pull 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 - "Using Scripts to Push a Change - Upstream and Request a Pull" and - "Using Email to Submit a Patch" - sections in the Yocto Project Development Manual. - - - - There are many ways to save kernel modifications. - The technique employed - depends on the destination for the patches: - - - Bulk storage - Internal sharing either through patches or by using Git - External submissions - Exporting for integration into another Source Code - Manager (SCM) - - - - - Because of the following list of issues, the destination of the patches also influences - the method for gathering them: - - - Bisectability - Commit headers - Division of subsystems for separate submission or review - - - -
- Bulk Export - - - 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. - - 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. - - - # 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 - - - - - 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. - - - - Once the changes are exported, you can restore them manually using a template - or through integration with the default_kernel. - - -
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- Incremental/Planned Sharing - - - 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. - - - - During development, the following commands are of interest. - For full Git documentation, refer to the Git documentation at - . - - - # 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. - - - - - 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 push and - pull operations for - distributed development, you should consider the ramifications of changing a - commit that you have already shared with others. - - - - 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: - - - $ Git add <path>/file - $ Git commit --amend - $ Git rebase or Git rebase -i - - - - - Again, assuming that the changes have not been pushed upstream, and that - no pending works-in-progress exist (use git status to check), then - you can revert (undo) commits by using the following commands: - - - # 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^ - - - - - 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 push or pull 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 kernel.org best - practices, which is recommended. - - 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. - - - -
- Exporting Changes Internally by Using Patches - - - 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. - - - - 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 - git am command to reproduce the original commit and all - the related information such as author, date, commit log, and so forth. - - 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. - - - # <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> - - - - - In other words: - - # 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> - - -
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- Exporting Changes Internally by Using Git - - - 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. - - - - Use this command form to push the changes: - - $ git push ssh://<master_server>/<path_to_repo> - <local_branch>:<remote_branch> - - - - - For example, the following command pushes the changes from your local branch - yocto/standard/common-pc/base to the remote branch with the same name - in the master repository //git.mycompany.com/pub/git/kernel-3.4. - - $ git push ssh://git.mycompany.com/pub/git/kernel-3.4 \ - yocto/standard/common-pc/base:yocto/standard/common-pc/base - - - - - A pull request entails using the git request-pull command to compose - an email to the - maintainer requesting that a branch be pulled into the master repository, see - for an example. - - Other commands such as git stash or branching can also be used to save - changes, but are not covered in this document. - - -
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- Exporting Changes for External (Upstream) Submission - - - 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. - - 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: - - - - Documentation/SubmittingPatches (in any linux - kernel source tree) - - - - - - 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 - "Submitting a Change to the Yocto Project" - section in the Yocto Project Development Manual. - - - - If the initial commits were not properly documented or do not meet those standards, - you can re-base by using the git rebase -i 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. - - - - 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 git send-email is commonly used to ensure - that patches are properly - formatted for easy application and avoid mailer-induced patch damage. - - - - The following is an example of dumping patches for external submission: - - # 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 - - -
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- Exporting Changes for Import into Another SCM - - - 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. - - - - 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. - -
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- Working with the Yocto Project Kernel in Another SCM - - - 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: - - The delivered Yocto Project kernel must be exported into the second - SCM. - Development must be exported from that secondary SCM into a - format that can be used by the OpenEmbedded build system. - - - -
- Exporting the Delivered Kernel to the SCM - - - 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. - - - - 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. - - - - The following commands illustrate some of the steps you could use to - import the yocto/standard/common-pc/base - kernel into a secondary SCM: - - $ git checkout yocto/standard/common-pc/base - $ cd .. ; echo linux/.git > .cvsignore - $ cvs import -m "initial import" linux MY_COMPANY start - - - - - You could now relocate the CVS repository and use it in a centralized manner. - - - - The following commands illustrate how you can condense and merge two BSPs into a - second SCM: - - $ 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 - - -
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- Importing Changes for the Build - - - 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. - -
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- Creating a BSP Based on an Existing Similar BSP - - - 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 "Creating a New BSP Layer Using the yocto-bsp Script" section in the - Yocto Project Board Support Package (BSP) Developer's Guide, or see the - Transcript:_creating_one_generic_Atom_BSP_from_another - wiki page. - - - - The basic steps you need to follow are: - - Make sure you have set up a local Source Directory: - You must create a local - Source Directory - by either creating a Git repository (recommended) or - extracting a Yocto Project release tarball. - Choose an existing BSP available with the Yocto Project: - 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 - . - Be sure you have the Base BSP: - 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. - Make a copy of the existing BSP, thus isolating your new - BSP work: - Copying the existing BSP file structure gives you a new area in which to work. - Make configuration and recipe changes to your new BSP: - Configuration changes involve the files in the BSP's conf - directory. - Changes include creating a machine-specific configuration file and editing the - layer.conf 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. - Prepare for the build: - 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 local.conf and bblayers.conf - files. - Build the image: - 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 bitbake - command. - - -
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- "-dirty" String - - - 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. - - $ git status - - - - - 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. - - - - To brute force pickup and commit all such pending changes, enter the following: - - $ git add . - $ git commit -s -a -m "getting rid of -dirty" - - - - - Next, rebuild the kernel. - -
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- - -- cgit v1.2.3-54-g00ecf