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| author | Scott Rifenbark <scott.m.rifenbark@intel.com> | 2010-11-29 07:28:51 -0800 |
|---|---|---|
| committer | Saul Wold <Saul.Wold@intel.com> | 2010-12-10 22:01:16 -0800 |
| commit | d2e540116f1cc0bf93b7ed6f4828c56ab909489e (patch) | |
| tree | 488a9fad0a793e4f0743e2296432744c82e0dd20 /documentation | |
| parent | c272830d8cc76835bbd2722848563244cc02f0f5 (diff) | |
| download | openembedded-core-d2e540116f1cc0bf93b7ed6f4828c56ab909489e.tar.gz openembedded-core-d2e540116f1cc0bf93b7ed6f4828c56ab909489e.tar.bz2 openembedded-core-d2e540116f1cc0bf93b7ed6f4828c56ab909489e.zip | |
documentation/kernel-manual/yocto-project-kernel-manual.xml: Removed this file so manual could be structured into a book with chapters.
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Diffstat (limited to 'documentation')
| -rw-r--r-- | documentation/kernel-manual/yocto-project-kernel-manual.xml | 2305 |
1 files changed, 0 insertions, 2305 deletions
diff --git a/documentation/kernel-manual/yocto-project-kernel-manual.xml b/documentation/kernel-manual/yocto-project-kernel-manual.xml deleted file mode 100644 index c0747b2540..0000000000 --- a/documentation/kernel-manual/yocto-project-kernel-manual.xml +++ /dev/null @@ -1,2305 +0,0 @@ -<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" -"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> - -<chapter id='kernel'> - -<title>Yocto Project Kernel Architecture and Use Manual</title> - -<section id='introduction'> - <title>Introduction</title> - <para> - Yocto Project presents the kernel as a fully patched, history-clean git - repository. - The git tree represents the selected features, board support, - and configurations extensively tested by Yocto Project. - The Yocto Project kernel allows the end user to leverage community - best practices to seamlessly manage the development, build and debug cycles. - </para> - <para> - This manual describes the Yocto Project kernel by providing information - on its history, organization, benefits, and use. - The manual consists of two sections: - <itemizedlist> - <listitem><para>Concepts - Describes concepts behind the kernel. - You will understand how the kernel is organized and why it is organized in - the way it is. You will understand the benefits of the 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>Using the Kernel - Describes best practices and "how-to" information - that lets you put the kernel to practical use. Some examples are "How to Build a - Project Specific Tree", "How to Examine Changes in a Branch", and "Saving Kernel - Modifications."</para></listitem> - </itemizedlist> - </para> - <para> - For more information on the kernel, see the following links: - <itemizedlist> - <listitem><para><ulink url='http://ldn.linuxfoundation.org/book/1-a-guide-kernel-development-process'></ulink></para></listitem> - <listitem><para><ulink url='http://userweb.kernel.org/~akpm/stuff/tpp.txt'></ulink></para></listitem> - <listitem><para><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> - You can find more information on Yocto Project by visiting the website at - <ulink url='http://www.yoctoproject.org'></ulink>. - </para> - </para> -</section> - -<section id='concepts'> - <title>Concepts</title> - <para> - This section provides conceptual information about the Yocto Project kernel: - <itemizedlist> - <listitem><para>Kernel Goals</para></listitem> - <listitem><para>Yocto Project Kernel Development and Maintenance Overview</para></listitem> - <listitem><para>Kernel Architecture</para></listitem> - <listitem><para>Kernel Tools</para></listitem> - </itemizedlist> - </para> - <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, flexibility and maintainability are key concerns. - The Yocto Project Linux kernel is presented with the embedded - developer's needs in mind and has 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 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 the most stable official release.</para></listitem> - <listitem><para>Include major technological features as part of Yocto Project's up-rev - strategy.</para></listitem> - <listitem><para>Present a git tree, that just like the upstream kernel.org 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 a specific use case (i.g. networking, consumer, devices, and so forth).</para></listitem> - <listitem><para>Employ a git branching strategy that from a customer's point of view - results in a linear path from the baseline kernel.org, 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> - Yocto Project kernel, like other kernels, is based off the Linux kernel release - from <ulink url='http://www.kernel.org'></ulink>. - At the beginning of our major development cycle, we choose our Yocto Project kernel - based on factors like release timing, the anticipated release timing of "final" (i.e. non "rc") - upstream kernel.org versions, and Yocto Project feature requirements. - Typically this will be a kernel that is in the - final stages of development by the community (i.e. still in the release - candidate or "rc" phase) and not yet a final release. - But by being in the final stages of external development, we know that the - kernel.org final release will clearly land within the early stages of - the Yocto Project development window. - </para> - <para> - This balance allows us to deliver the most up-to-date kernel - as possible, while still ensuring that we have a stable official release as - our baseline kernel version. - </para> - <para> - The following figure represents the overall place the Yocto Project kernel fills. - </para> - <para> - <imagedata fileref="figures/kernel-big-picture.png" width="6in" depth="6in" align="center" scale="100" /> - </para> - <para> - In the figure the ultimate source for the Yocto Project kernel is a released kernel - from kernel.org. - In addition to a foundational kernel from kernel.org the commercially released - Yocto Project kernel contains a mix of important new mainline - developments, non-mainline developments, Board Support Package (BSP) developments, - and custom features. - These additions result in a commercially released Yocto Project kernel that caters - to specific embedded designer needs for targeted hardware. - </para> - <para> - Once a Yocto Project kernel is officially released the Yocto Project team goes into - their next development cycle, or "uprev" cycle. - 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 of hundreds of individual fixes and minor features from various - kernel versions is not sustainable and can easily compromise quality. - 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 kernel.org version. - The team continually monitors community kernel - development to look for significant features of interest. - The illustration depicts this by showing the team looking back to kernel.org for new features, - BSP features, and significant bug fixes. - 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 simply 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 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 very special - cases for BSP and feature development. - </para> - </section> - - <section id='kernel-architecture'> - <title>Kernel Architecture</title> - <para> - This section describes the architecture of the Yocto Project kernel 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 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 kernel.org. - - </para> - <para> - You can think of the Yocto Project kernel as consisting of a baseline 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. - 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 as well. - </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> - 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 user - 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. - 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 results in not having to store the same feature twice internally in the - tree. - Rather we store the unique differences required to apply the feature onto the kernel type - in question. - </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, we create 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, only the unique differences for the BSP across - the supported multiple kernels are uniquely stored. - </para> - <para> - While this strategy results in a tree with a significant number of branches, it is - important to realize that from the customer's point of view, there is a linear - path that travels from the baseline kernel.org, through a select group of features and - ends with their BSP-specific commits. - In other words, the divisions of the kernel are transparent and are not relevant - to the developer on a day-to-day basis. - From the customer's perspective, this is the "master" branch. - They do not need not 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 diff 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 user - 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 and it is the obvious mechanism for meeting the - previously mentioned goals. - Not only is it the SCM for kernel.org but git continues to grow in popularity and - supports many different work flows, front-ends and management techniques. - </para> - <note><para> - It should be noted that you can use as much, or as little, of what git has to offer - as is appropriate to your project. - </para></note> - </section> - </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 -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> -The fundamental properties of the tools that manage and construct the -kernel are: -<itemizedlist> - <listitem><para>the ability to group patches into named, reusable features</para></listitem> - <listitem><para>to allow top down control of included features</para></listitem> - <listitem><para>the binding of kernel configuration to kernel patches/features</para></listitem> - <listitem><para>the presentation of a seamless git repository that blends Yocto Project value with the kernel.org history and development</para></listitem> -</itemizedlist> -</para> -<!--<para> -The tools that construct a kernel tree will be discussed later in this -document. The following tools form the foundation of the Yocto Project -kernel toolkit: -<itemizedlist> - <listitem><para>git : distributed revision control system created by Linus Torvalds</para></listitem> - <listitem><para>guilt: quilt on top of git</para></listitem> - <listitem><para>*cfg : kernel configuration management and classification</para></listitem> - <listitem><para>kgit*: Yocto Project kernel tree creation and management tools</para></listitem> - <listitem><para>scc : series & configuration compiler</para></listitem> -</itemizedlist> -</para> --> - </section> -</section> - - - - -<!-- <section id='concepts2'> - <title>Kernel Concepts</title> - <itemizedlist> - <listitem><para>What tools and commands are used with the kernel.</para></listitem> - <listitem><para>Source Control Manager (SCM).</para></listitem> - <listitem><para>What are some workflows that you can apply using the kernel.</para></listitem> - </itemizedlist> -</section> --> - -<section id='actions'> - <title>How to Get Things Accomplished with the Kernel</title> - <para> - This section describes how to accomplish tasks involving the kernel's tree structure. - The information covers the following: - <itemizedlist> - <listitem><para>Tree construction</para></listitem> - <listitem><para>Build strategies</para></listitem> -<!-- <listitem><para>Series & Configuration Compiler</para></listitem> - <listitem><para>kgit</para></listitem> --> - <listitem><para>Workflow examples</para></listitem> - <listitem><para>Source Code Manager (SCM)</para></listitem> -<!-- <listitem><para>Board Support Package (BSP) template migration</para></listitem> --> - <listitem><para>BSP creation</para></listitem> - <listitem><para>Patching</para></listitem> - <listitem><para>Updating BSP patches and configuration</para></listitem> -<!-- <listitem><para>guilt</para></listitem> - <listitem><para>scc file example</para></listitem> --> - <listitem><para>"dirty" string</para></listitem> -<!-- <listitem><para>Transition kernel layer</para></listitem> --> - </itemizedlist> - </para> - - <section id='tree-construction'> - <title>Tree Construction</title> - <para> -The Yocto Project kernel repository, as shipped with the product, is created 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 the kernel. -</para> -<para> -The files used to describe all the valid features and BSPs in the Yocto Project -kernel can be found in any clone of the kernel git tree. The directory -wrs/cfg/kernel-cache/ is a snapshot of all the kernel configuration and -feature descriptions (.scc) that were used to build the kernel repository. -It should however be noted, that browsing the snapshot of feature -descriptions and patches is not an effective way to determine what is in a -particular kernel branch. Using git directly to get insight into the changes -in a branch is more efficient and a more flexible way to inspect changes to -the kernel. Examples of using git to inspect kernel commits are in the -following sections. -</para> -<para> -As a reminder, it is envisioned that a ground up reconstruction of the -complete kernel tree is an action only taken by Yocto Project team during an -active development cycle. When an end user creates a project, it takes -advantage of this complete tree in order to efficiently place a git tree -within their project. -</para> -<para> -The general flow of the project specific kernel tree construction is as follows: -<orderedlist> - <listitem><para>a top level kernel feature is passed to the kernel build subsystem, - normally this is a BSP for a particular kernel type.</para></listitem> - - <listitem><para>the file that describes the top level feature is located by searching - system directories:</para> - - <itemizedlist> - <listitem><para>the kernel-cache under linux/wrs/cfg/kernel-cache</para></listitem> -<!-- <listitem><para>kernel-*-cache directories in layers</para></listitem> --> - <listitem><para>recipe SRC_URIs</para></listitem> -<!-- <listitem><para>configured and default templates</para></listitem> --> - </itemizedlist> - - <para>In a typical build a feature description of the format: - <bsp name>-<kernel type>.scc is the target of the search. - </para></listitem> - - <listitem><para>once located, the feature description is compiled into a simple script - of actions, or an existing equivalent script which was part of the - shipped kernel is located.</para></listitem> - - <listitem><para>extra features are appended to the top level feature description. Extra - features can come from the KERNEL_FEATURES variable in recipes.</para></listitem> - - <listitem><para>each extra feature is located, compiled and appended to the script from - step #3</para></listitem> - - <listitem><para>the script is executed, and a meta-series is produced. The meta-series - is a description of all the branches, tags, patches and configuration that - need to be applied to the base git repository to completely create the - "bsp_name-kernel_type".</para></listitem> - - <listitem><para>the base repository is cloned, and the actions - listed in the meta-series 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 tree is now ready for configuration and compilation. Those two topics will -be covered below. -</para> - -<note><para>The end user generated meta-series adds to the kernel as shipped with - the Yocto Project release. Any add-ons and configuration data are applied - to the end of an existing branch. The full repository generation that - is found in the linux-2.6-windriver.git is the combination of all - supported boards and configurations. -</para></note> - -<para> -This technique is flexible and allows the seamless blending of an immutable -history with additional deployment specific patches. Any additions to the -kernel become an integrated part of the branches. -</para> - -<!-- <note><para>It is key that feature descriptions indicate if any branches are - required, since the build system cannot automatically decide where a - BSP should branch or if that branch point needs a name with - significance. There is a single restriction enforced by the compilation - phase: - </para> - <para>A BSP must create a branch of the format <bsp name>-<kernel type>.</para> - - <para>This means that all merged/support BSPs must indicate where to start - its branch from, with the right name, in its .scc files. The scc - section describes the available branching commands in more detail. - </para> -</note> --> - -<para> -A summary of end user tree construction activities follow: -<itemizedlist> - <listitem><para>compile and link a full top-down kernel description from feature descriptions</para></listitem> - <listitem><para>execute the complete description to generate a meta-series</para></listitem> - <listitem><para>interpret the meta-series to create a customized git repository for the - board</para></listitem> - <listitem><para>migrate configuration fragments and configure the kernel</para></listitem> - <listitem><para>checkout the BSP branch and build</para></listitem> -</itemizedlist> -</para> - </section> - - <section id='build-strategy'> - <title>Build Strategy</title> -<para> -There are some prerequisites that must be met before starting the compilation -phase of the kernel build system: -</para> -<itemizedlist> - <listitem><para>There must be a kernel git repository indicated in the SRC_URI.</para></listitem> - <listitem><para>There must be a branch <bsp name>-<kernel type>.</para></listitem> -</itemizedlist> - -<para> -These are typically met by running tree construction/patching phase of the -build system, but can be achieved by other means. Examples of alternate work -flows such as bootstrapping a BSP are provided below. -</para> -<para> -Before building a kernel it is configured by processing all of the -configuration "fragments" specified by the scc feature descriptions. As the -features are compiled, associated kernel configuration fragments are noted -and recorded in the meta-series 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 that will -be used during compilation. -</para> -<para> -Kernel compilation is started, using the board's architecture and other -relevant values from the board template, and a kernel image is produced. -</para> -<para> -The other thing that you will first see once you configure a kernel is that -it will generate a build tree that is separate from your git source tree. -This build dir will be called "linux-<BSPname>-<kerntype>-build" where -kerntype is one of standard kernel types. This functionality is done by making -use of the existing support that is within the kernel.org tree by default. -</para> -<para> -What this means, is that all the generated files (that includes the final -".config" itself, all ".o" and ".a" etc) are now in this directory. Since -the git source tree can contain any number of BSPs, all on their own branch, -you now can easily switch between builds of BSPs as well, since each one also -has their own separate build directory. -</para> - </section> - -<!-- <section id='scc'> - <title>Series & Configuration Compiler (SCC)</title> -<para> -In early versions of the product, kernel patches were simply listed in a flat -file called "patches.list", and then quilt was added as a tool to help -traverse this list, which in quilt terms was called a "series" file. -</para> -<para> -Before the 2.0 release, it was already apparent that a static series file was -too inflexible, and that the series file had to become more dynamic and rely -on certain state (like kernel type) in order to determine whether a patch was -to be used or not. The 2.0 release already made use of some stateful -construction of series files, but since the delivery mechanism was unchanged -(tar + patches + series files), most people were not aware of anything really -different. The 3.0 release continues with this stateful construction of -series files, but since the delivery mechanism is changed (git + branches) it -now is more apparent to people. -</para> -<para> -As was previously mentioned, scc is a "series and configuration -compiler". Its role is to combine feature descriptions into a format that can -be used to generate a meta-series. A meta series contains all the required -information to construct a complete set of branches that are required to -build a desired board and feature set. The meta series is interpreted by the -kgit tools to create a git repository that could be built. -</para> -<para> -To illustrate how scc works, a feature description must first be understood. -A feature description is simply a small bash shell script that is executed by -scc in a controlled environment. Each feature description describes a set of -operations that add patches, modify existing patches or configure the -kernel. It is key that feature descriptions can include other features, and -hence allow the division of patches and configuration into named, reusable -containers. -</para> -<para> -Each feature description can use any of the following valid scc commands: -<itemizedlist> - <listitem><para>shell constructs: bash conditionals and other utilities can be used in a feature - description. During compilation, the working directory is the feature - description itself, so any command that is "raw shell" and not from the - list of supported commands, can not directly modify a git repository.</para></listitem> - - <listitem><para>patch <relative path>/<patch name>: outputs a patch to be included in a feature's patch set. Only the name of - the patch is supplied, the path is calculated from the currently set - patch directory, which is normally the feature directory itself.</para></listitem> - - <listitem><para>patch_trigger >condition< >action< <tgt>: indicate that a trigger should be set to perform an action on a - patch.</para> - -<para>The conditions can be: - - <itemizedlist> - <listitem><para>arch:<comma separated arch list or "all"></para></listitem> - <listitem><para>plat:<comma separated platform list or "all"></para></listitem> - </itemizedlist></para> -<para>The action can be: - <itemizedlist> - <listitem><para>exclude: This is used in exceptional situations where a patch - cannot be applied for certain reasons (arch or platform). - When the trigger is satisfied the patch will be removed from - the patch list.</para></listitem> - <listitem><para>include: This is used to include a patch only for a specific trigger. - Like exclude, this should only be used when necessary. - It takes 1 argument, the patch to include.</para></listitem> - </itemizedlist></para></listitem> - - <listitem><para>include <feature name> [after <feature>]: includes a feature for processing. The feature is "expanded" at the - position of the include directive. This means that any patches, - configuration or sub-includes of the feature will appear in the final - series before the commands that follow the include.</para> - <para> - include searches the include directories for a matching feature name, - include directories are passed to scc by the caller using -I <path> and - is transparent to the feature script. This means that <feature name> must - be relative to one of the search paths. For example, if - /opt/kernel-cache/feat/sched.scc is to be included and scc is invoked - with -I /opt/kernel-cache, then a feature would issue "include - feat/sched.scc" to include the feature. -</para> -<para> - The optional "after" directive allows a feature to modify the existing - order of includes and insert a feature after the named feature is - processed. Note: the "include foo after bar" must be issued before "bar" - is processed, so is normally only used by a new top level feature to - modify the order of features in something it is including.</para></listitem> - - <listitem><para>exclude <feature name>: Indicates that a particular feature should *not* be included even if an - 'include' directive is found. The exclude must be issued before the - include is processed, so is normally only used by a new top level feature - to modify the order of features in something it is including.</para></listitem> - - <listitem><para>git <command>: Issues any git command during tree construction. Note: this command is - not validated/sanitized so care must be taken to not damage the - tree. This can be used to script branching, tagging, pulls or other git - operations.</para></listitem> - - <listitem><para>dir <directory>: changes the working directory for "patch" directives. This can be used to - shorten a long sequence of patches by not requiring a common relative - directory to be issued each time.</para></listitem> - - <listitem><para>kconf <type> <fragment name>: associates a kernel config frag with the feature. - <type> can be - "hardware" or "non-hardware" and is used by the kernel configuration - subsystem to audit configuration. <fragment name> is the name of a file - in the current feature directory that contains a series of kernel - configuration options. There is no restriction on the chosen fragment - name, although a suffix of ".cfg" is recommended. Multiple fragment - specifications are supported.</para></listitem> - - <listitem><para>branch <branch name>: creates a branch in the tree. All subsequent patch commands will be - applied to the new branch and changes isolated from the rest of the - repository.</para></listitem> - - <listitem><para>scc_leaf <base feature> <branch name>: Performs a combination feature include and branch. This is mainly a - convenience directive, but has significance to some build system bindings - as a sentinel to indicate that this intends to create a branch that is - valid for kernel compilation.</para></listitem> - - <listitem><para>tag <tag name>: Tags the tree. The tag will be applied in processing order, so will - be after already applied patches and precede patches yet to be applied.</para></listitem> - - <listitem><para>define <var> <value>: Creates a variable with a particular value that can be used in subsequent - feature descriptions.</para></listitem> -</itemizedlist> - -</para> - </section> --> - -<!-- <section id='kgit-tools'> - <title>kgit Tools</title> -<para> -The kgit tools are responsible for constructing and maintaining the Wind -River kernel repository. These activities include importing, exporting, and -applying patches as well as sanity checking and branch management. From the -developers perspective, the kgit tools are hidden and rarely require -interactive use. But one tool in particular that warrants further description -is "kgit-meta". -</para> -<para> -kgit-meta is the actual application of feature description(s) to a kernel repo. -In other words, it is responsible for interpreting the meta series generated -from a scc compiled script. As a result, kgit-meta is coupled to the set of -commands permitted in a .scc feature description (listed in the scc section). -kgit-meta understands both the meta series format and how to use git and -guilt to modify a base git repository. It processes a meta-series line by -line, branching, tagging, patching and tracking changes that are made to the -base git repository. -</para> -<para> -Once kgit-meta has processed a meta-series, it leaves the repository with the -last branch checked out, and creates the necessary guilt infrastructure to -inspect the tree, or add to it via using guilt. As was previously mentioned, -guilt is not required, but is provided as a convenience. Other utilities such -as quilt, stgit, git or others can also be used to manipulate the git -repository. -</para> - </section> --> - - <section id='workflow-examples'> - <title>Workflow Examples</title> - - <para> -As previously noted, the Yocto Project kernel has built in git/guilt -integration, but these utilities are not the only way to work with the kernel -repository. Yocto Project has not made changes to git, or other tools that -invalidate alternate workflows. Additionally, the way the kernel repository -is constructed uses only core git functionality allowing any number of tools -or front ends to use the resulting tree.</para> -<para> -This section contains several workflow examples. -</para> - - <section id='change-inspection-kernel-changes-commits'> - <title>Change Inspection: Kernel Changes/Commits</title> -<para> -A common question when working with a BSP/kernel is: "What changes have been applied to this tree?" -</para> -<para> -In some projects, where a collection of directories that -contained patches to the kernel, those patches could be inspected, grep'd or -otherwise used to get a general feeling for changes. This sort of patch -inspection is not an efficient way to determine what has been done to the -kernel, since there are many optional patches that are selected based on the -kernel type and feature description, not to mention patches that are actually -in directories that are not being searched. -</para> -<para> -A more effective way to determine what has changed in the kernel is to use -git and inspect / search the kernel tree. This is a full view of not only the -source code modifications, but the reasoning behind the changes. -</para> - <section id='what-changed-in-a-bsp'> - <title>What Changed in a BSP?</title> -<para> -These examples could continue for some time, since the Yocto Project git -repository doesn't break existing git functionality and there are nearly -endless permutations of those commands. Also note that unless a commit range -is given (<kernel type>..<bsp>-<kernel type>), kernel.org history is blended -with Yocto Project changes -</para> -<literallayout class='monospaced'> - # full description of the changes - > git whatchanged <kernel type>..<bsp>-<kernel type> - > eg: git whatchanged standard..common_pc-standard - - # summary of the changes - > git log ‐‐pretty=oneline ‐‐abbrev-commit <kernel type>..<bsp>-<kernel type> - - # source code changes (one combined diff) - > git diff <kernel type>..<bsp>-<kernel type> - > git show <kernel type>..<bsp>-<kernel type> - - # dump individual patches per commit - > git format-patch -o <dir> <kernel type>..<bsp>-<kernel type> - - # determine the change history of a particular file - > git whatchanged <path to file> - - # determine the commits which touch each line in a file - > git blame <path to file> -</literallayout> - </section> - - <section id='show-a-particular-feature-or-branch-change'> - <title>Show a Particular Feature or Branch Change</title> -<para> -Significant features or branches are tagged in the Yocto Project tree to divide -changes. Remember to first determine (or add) the tag of interest. Note: -there will be many tags, since each BSP branch is tagged, kernel.org tags and -feature tags are all present. -</para> -<literallayout class='monospaced'> - # show the changes tagged by a feature - > git show <tag> - > eg: git show yaffs2 - - # determine which branches contain a feature - > git branch ‐‐contains <tag> - - # show the changes in a kernel type - > git whatchanged wrs_base..<kernel type> - > eg: git whatchanged wrs_base..standard -</literallayout> -<para> -Many other comparisons can be done to isolate BSP changes, such as comparing -to kernel.org tags (v2.6.27.18, etc), per subsystem comparisons (git -whatchanged mm) or many other types of checks. -</para> - </section> - </section> - - <section id='development-saving-kernel-modifications'> - <title>Development: Saving Kernel Modifications</title> -<para> -Another common operation is to build a Yocto Project supplied BSP, make some -changes, rebuild and 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 -greatly simplified and is much easier than in previous releases. git tracks -file modifications, additions and deletions, which allows the developer to -modify the code and later realize that the changes should be saved, and -easily determine what was changed. It also provides many tools to commit, -undo and export those modifications. -</para> -<para> -There are many ways to perform this action, and the technique employed -depends on the destination for the patches, which could be any of: -<itemizedlist> - <listitem><para>bulk storage</para></listitem> - <listitem><para>internal sharing either through patches or using git</para></listitem> - <listitem><para>external submission</para></listitem> - <listitem><para>export for integration into another SCM</para></listitem> -</itemizedlist> -</para> -<para> -The destination of the patches also incluences the method of gathering them -due to issues such as: -<itemizedlist> - <listitem><para>bisectability</para></listitem> - <listitem><para>commit headers</para></listitem> - <listitem><para>division of subsystems for separate submission / review</para></listitem> -</itemizedlist> -</para> - - <section id='bulk-export'> - <title>Bulk Export</title> -<para> -If patches are simply being stored outside of the kernel source repository, -either permanently or temporarily, then there are several methods that can be -used. -</para> -<para> -Note the "bulk" in this discussion, these techniques are not appropriate for -full integration of upstream submission, since they do not properly divide -changes or provide an avenue for per-change commit messages. This example -assumes that changes have not been committed incrementally during development -and simply must be gathered and exported. -<literallayout class='monospaced'> - # bulk export of ALL modifications without separation or division - # of the changes - - > git add . - > git commit -s -a -m >commit message< - or - > git commit -s -a # and interact with $EDITOR -</literallayout> -</para> -<para> -These operations have captured 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 exported, those changes can then be restored manually, via a template or -through integration with the default_kernel. Those topics are covered in -future sections. -</para> - </section> - - <section id='incremental-planned-sharing'> - <title>Incremental/Planned Sharing</title> -<para> -Note: unlike the previous "bulk" section, the following examples assume that -changes have been incrementally committed to the tree during development and -now are being exported. -</para> -<para> -During development the following commands will be of interest, but for full -git documentation refer to the git man pages or an online resource such as -http://github.com -<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 by having a universally agreed -upon unique commit identifier (set by the creator of the commit) mapping to a -specific changeset with a specific parent. This ID is created for you when -you create a commit, and will be re-created when you amend/alter or re-apply -a commit. As an individual in isolation, this is of no interest, but if you -intend to share your tree with normal git push/pull operations for -distributed development, you should consider the ramifications of changing a -commit that you've already shared with others. -</para> -<para> -Assuming that the changes have *not* been pushed upstream, or pulled into -another repository, both the commit content and commit messages associated -with development can be update via: -<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 -there are no pending works in progress (use "git status" to check) then -commits can be reverted (undone) via: -<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> -Branches can be created, changes cherry-picked or any number of git -operations performed until the commits are in good order for pushing upstream -or pull requests. After a push or pull, commits are normally considered -'permanent' and should not be modified, only incrementally changed in new -commits. This is standard "git" workflow and Yocto Project recommends the -kernel.org best practices. -</para> -<note><para>It is recommend to tag or branch before adding changes to a Yocto Project - BSP (or creating a new one), since the branch or tag provides a - reference point to facilitate locating and exporting local changes. -</para></note> - - <section id='export-internally-via-patches'> - <title>Export Internally Via Patches</title> -<para> -Committed changes can be extracted from a working directory by exporting them -as patches. Those patches can be used for upstream submission, placed in a -Yocto Project template for automatic kernel patching or many other common uses. - -<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> - -<para> -The result is a directory with sequentially numbered patches, that when -applied to a repository using "git am", will reproduce the original commit -and all related information (author, date, commit log, etc) will be -preserved. Note that new commit IDs will be generated upon reapplication, -reflecting that the commit is now applied to an underlying commit with a -different ID. -</para> -<!--<para> -See the "template patching" example for how to use the patches to -automatically apply to a new kernel build. -</para> --> - </section> - - <section id='export-internally-via-git'> - <title>Export Internally Via git</title> -<para> -Committed changes can also be exported from a working directory by pushing -(or by making a pull request) the changes into a master repository. Those -same change can then be pulled into a new kernel build at a later time using this command form: -<literallayout class='monospaced'> - git push ssh://<master server>/<path to repo> <local branch>:<remote branch> -</literallayout> -For example: -<literallayout class='monospaced'> - > push ssh://git.mycompany.com/pub/git/kernel-2.6.27 common_pc-standard:common_pc-standard -</literallayout> -A pull request entails using "git request-pull" to compose an email to the -maintainer requesting that a branch be pulled into the master repository, see -http://github.com/guides/pull-requests for an example. -</para> -<para> -Other commands such as 'git stash' or branching can also be used to save -changes, but are not covered in this document. -</para> -<para> -See the section "importing from another SCM" for how a git push to the -default_kernel, can be used to automatically update the builds of all users -of a central git repository. -</para> - </section> - </section> - - <section id='export-for-external-upstream-submission'> - <title>Export for External (Upstream) Submission</title> -<para> -If patches are to be sent for external submission, they can be done via a -pull request if the patch series is large or the maintainer prefers to pull -changes. But commonly, patches are sent as email series for easy review and -integration. -</para> -<note><para> -Before sending patches for review ensure that you understand the -standard of the community in question and follow their best practices. For -example, kernel patches should follow standards such as: -<itemizedlist> - <listitem><para><ulink url='http://userweb.kernel.org/~akpm/stuff/tpp.txt'></ulink></para></listitem> - <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> -</para></note> -<para> -The messages used to commit changes are a large part of these standards, so -ensure that the headers for each commit have the required information. If the -initial commits were not properly documented or don't meet those standards -rebasing via git rebase -i offer an opportunity 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 complete, patches are sent via email to the maintainer(s) or lists that -review and integrate changes. "git send-email" is commonly used to ensure -that patches are properly formatted for easy application and avoid mailer -induced patch damage. -</para> -<para> -An example of dumping patches for external submission follows: -<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>Export for Import into Other SCM</title> -<para> -Using any one of the previously discussed techniques, commits can be exported -as patches for import into another SCM. Note however, that if those patches -are manually applied to a secondary tree and then that secondary tree is -checked into the SCM, then it often results in lost information (like commit -logs) and so it is not recommended. -</para> -<para> -Many SCMs can directly import git commits, or can translate git patches to -not lose information. Those facilities are SCM dependent and should be used -whenever possible. -</para> - </section> - </section> - - <section id='scm-working-with-the-yocto-project-kernel-in-another-scm'> - <title>SCM: Working with the Yocto Project Kernel in Another SCM</title> -<para> -This is not the same as the exporting of patches to another SCM, but instead -is concerned with kernel development that is done completely in another -environment, but built with the Yocto Project build system. In this scenario two -things must happen: -<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 Yocto Project build system.</para></listitem> -</itemizedlist> -</para> - <section id='exporting-delivered-kernel-to-scm'> - <title>Exporting Delivered Kernel to SCM</title> -<para> -Depending on the SCM it may be possible to export the entire Yocto Project -kernel git repository, branches and all, into a new environment. This is the -preferred method, since 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 that could be used to -import the common_pc-standard kernel into a secondary SCM -<literallayout class='monospaced'> - > git checkout common_pc-standard - > cd .. ; echo linux/.git > .cvsignore - > cvs import -m "initial import" linux MY_COMPANY start -</literallayout> -The CVS repo could now be relocated and used in a centralized manner. -</para> -<para> -The following commands illustrate how two BSPs could be condensed and merged -into a second SCM: -<literallayout class='monospaced'> - > git checkout common_pc-standard - > git merge cav_ebt5800-standard - # 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 Build</title> -<para> -Once development has reached a suitable point in the second development -environment, changes can either be exported as patches or imported into git -directly (if a conversion/import mechanism is available for the SCM). -</para> -<para> -If changes are exported as patches, they can be placed in a recipe and -automatically applied to the kernel during patching. -</para> -<!--<para> -If changes are imported directly into git, they must be propagated to the -wrll-linux-2.6.27/git/default_kernel bare clone of each individual build -to be present when the kernel is checked out. -</para> -<para> -The following example illustrates one variant of this workflow: -<literallayout class='monospaced'> - # on master git repository - > cd linux-2.6.27 - > git tag -d common_pc-standard-mark - > git pull ssh://<foo>@<bar>/pub/git/kernel-2.6.27 common_pc-standard:common_pc-standard - > git tag common_pc-standard-mark - - # on each build machine (or NFS share, etc) - > cd wrll-linux-2.6.27/git/default_kernel - > git fetch ssh://<foo>@<master server>/pub/git/kernel-2.6.27 - - # in the build, perform a from-scratch build of Linux and the new changes - # will be checked out and built. - > make linux -</literallayout> -</para> --> - </section> - </section> - -<!-- <section id='bsp-template-migration-from-2'> - <title>BSP: Template Migration from 2.0</title> -<para> -The move to a git-backed kernel build system in 3.0 introduced a small new -requirement for any BSP that is not integrated into the GA release of the -product: branching information. -</para> -<para> -As was previously mentioned in the background sections, branching information -is always required, since the kernel build system cannot make intelligent -branching decisions and must rely on the developer. This branching -information is provided via a .scc file. -</para> -<para> -A BSP template in 2.0 contained build system information (config.sh, etc) and -kernel patching information in the 'linux' subdirectory. The same holds true -in 3.0, with only minor changes in the kernel patching directory. -The ".smudge" files are now ".scc" files and now contain a full description - of the kernel branching, patching and configuration for the BSP. Where in - 2.0, they only contained kernel patching information. -</para> -<para> -The following illustrates the migration of a simple 2.0 BSP template to the -new 3.0 kernel build system. -</para> -<note><para> -Note: all operations are from the root of a customer layer. -</para></note> -<literallayout class='monospaced'> - templates/ - `‐‐ board - `‐‐ my_board - |‐‐ config.sh - |‐‐ include - `‐‐ linux - `‐‐ 2.6.x - |‐‐ knl-base.cfg - |‐‐ bsp.patch - `‐‐ my_bsp.smudge - - > mv templates/board/my_board/linux/2.6.x/* templates/board/my_board/linux - > rm -rf templates/board/my_board/linux/2.6.x/ - > mv templates/board/my_board/linux/my_bsp.smudge \ - templates/board/my_board/linux/my_bsp-standard.scc - > echo "kconf hardware knl-base.cfg" >> \ - templates/board/my_board/linux/my_bsp-standard.scc - > vi templates/board/my_board/linux/my_bsp-standard.scc - # add the following at the top of the file - scc_leaf ktypes/standard my_bsp-standard - - templates/ - `‐‐ board - `‐‐ my_board - |‐‐ config.sh - |‐‐ include - `‐‐ linux - |‐‐ knl-base.cfg - |‐‐ bsp.patch - `‐‐ my_bsp-standard.scc -</literallayout> -<para> -That's it. Configure and build. -</para> -<note><para>There is a naming convention for the .scc file, which allows the build - system to locate suitable feature descriptions for a board: -</para></note> -<literallayout class='monospaced'> - <bsp name>-<kernel type>.scc -</literallayout> -<para> - if this naming convention isn't followed your feature description will - not be located and a build error thrown. -</para> - </section> --> - - - - <section id='bsp-creating'> - <title>BSP: Creating</title> - <para> - This section provides an example for creating a BSP based on an existing, and hopefully, - similar one. - Follow these steps and keep in mind your particular situation and differences: - <orderedlist> - <listitem><para>Get a machine configuration file that matches your machine.</para> - <para>You can start with something in <filename>meta/conf/machine</filename>. - Or, <filename>meta-emenlow/conf/machine</filename> has an example in its own layer.</para> - <para>The most up-to-date machines that are probably most similar to yours and that you might want - to look at are <filename>meta/conf/machine/atom-pc.conf</filename> and - <filename>meta-emenlow/conf/machine/emenlow.conf</filename>. - Both of these were either just added or upgraded to use the Yocto Project kernel - at <ulink url='http://git.pokylinux.org/cgit/cgit.cgi/linux-2.6-windriver/'></ulink>. - The main difference between them is that "emenlow" is in its own layer. - It is in its own layer because it needs extra machine-specific packages such as its - own video driver and other supporting packages. - The "atom-pc" is simpler and does not need any special packages - everything it needs can - be specified in the configuration file. - The "atom-pc" machine also supports all of Asus eee901, Acer Aspire One, Toshiba NB305, - and the Intel® Embedded Development Board 1-N450 with no changes.</para> - <para>If you want to make minor changes to support a slightly different machine, you can - create a new configuration file for it and add it alongside the others. - You might consider keeping the common stuff separate and including it.</para> - <para>Similarly, you can also use multiple configuration files for different machines even - if you do it as a separate layer like meta-emenlow.</para> - <para>As an example consider this: - <itemizedlist> - <listitem><para>Copy meta-emenlow</para></listitem> - <listitem><para>Fix or remove anything you do not need. - For this example the only thing left was the kernel directory with a linux-yocto_git.bbappend - file (linux-yocto is the kernel listed in - <filename>meta-crownbay/conf/machine/crownbay.conf</filename>. - Finally, a new entry to the <filename>build/donf/bblayers.conf</filename> was added so the - new layer could be found by Bitbake.</para></listitem> - </itemizedlist> - </para></listitem> - <listitem><para>Get an image with a working kernel built.</para> - <para>For the kernel to compile successfully, you need to create a branch in the git repository - specifically named for your machine. - So first create a bare clone of the Yocto Project git repository, and then create a - local clone of that: - <literallayout class='monospaced'> - $ git clone ‐‐bare git://git.pokylinux.org/linux-2.6-windriver.git - linux-2.6-windriver.git - $ git clone linux-2.6-windriver.git linux-2.6-windriver - </literallayout> - </para> - <para>Now create a branch in the local clone and push it to the bare clone: - <literallayout class='monospaced'> - $ git checkout -b crownbay-standard origin/standard $ git push origin crownbay-standard:crownbay-standard - </literallayout> - </para> - <para>At this point, your git tree should be set up well enough to compile.</para></listitem> - <listitem><para>Point the build at the new kernel git tree.</para> - <para>You can do this by commenting out the SRC_URI variable in - <filename>meta/recipes-kernel/linux/linux-yocto_git.bb</filename> and using a SRC_URI - that points to your new bare git tree. - You should also be able to do this in <filename>linux-yocto_git.bbappend</filename> in the layer: - <literallayout class='monospaced'> - # To use a staged, on-disk bare clone of a Wind River Kernel, use a variant of the - # below SRC_URI = "git://///path/to/kernel/default_kernel.git;fullclone=1" - # - SRC_URI = "git://git.pokylinux.org/linux-2.6-windriver.git;protocol=git;fullclone=1;branch=${KBRANCH};name=machine -\ - git://git.pokylinux.org/linux-2.6-windriver.git;protocol=git;noclone=1;branch=wrs_meta;name=meta" - </literallayout> - </para> - <para>After doing that, select the machine in <filename>build/conf/local.conf</filename>: - <literallayout class='monospaced'> - # - MACHINE ?= "crownbay" - # - </literallayout> - </para> - <para>You should now be able to build and boot an image with the new kernel: - <literallayout class='monospaced'> - $ bitbake poky-image-sato-live - </literallayout> - </para> - <para>Of course, that will give you a kernel with the default config, which is probably - not what you want. - If you just want to set some kernel config options, you can do that by putting them in a files. - For example inserting the following into some <filename>.cfg</filename> file: - <literallayout class='monospaced'> - CONFIG_NETDEV_1000=y - CONFIG_E1000E=y - </literallayout> - </para> - <para>And, another <filename>.cfg</filename> file would contain: - <literallayout class='monospaced'> - CONFIG_LOG_BUF_SHIFT=18 - - http://git.pokylinux.org/cgit/cgit.cgi/linux-2.6-windriver/ - - SRC_URI_append_crownbay = " file://some.cfg \ - file://other.cfg \ - " - </literallayout> - </para> - <para>You could also add these directly to the git repo's wrs_meta branch as well. - However, the former method is probably easier.</para></listitem> - <listitem><para>If you're also adding patches to the kernel, you can do the same thing. - Put your patches in the SRC_URI as well (plus .cfg for their kernel config options if needed).</para> - <para>Practically speaking, to generate the patches, you'd go to the source in the build tree: - <literallayout class='monospaced'> - build/tmp/work/crownbay-poky-linux/linux-yocto-2.6.34+git0+d1cd5c80ee97e81e130be8c3de3965b770f320d6_0+ -0431115c9d720fee5bb105f6a7411efb4f851d26-r13/linux - </literallayout> - </para> - <para>Then, modify the code there, using quilt to save the changes, and recompile - (bitbake -c compile -f) - until it works.</para></listitem> - <listitem><para>Once you have the final patch from quilt, copy it to the - SRC_URI location, and it should be - applied the next time you do a clean build. - Of course, since you have a branch for the BSP in git, it would be better to put it there instead. - For example, in this case, commit the patch to the crownbay-standard branch, and during the - next build it will be applied from there.</para></listitem> - </orderedlist> - </para> - </section> - - - - - - - - -<!-- <section id='bsp-creating-a-new-bsp'> - <title>BSP: Creating a New BSP</title> -<para> -Although it is obvious that the structure of a new BSP uses the migrated -directory structure from the previous example,the first question is whether -or not the BSP is started from scratch. -</para> -<para> -If Yocto Project has a similar BSP, it is often easier to clone and update, -rather than start from scratch. If the mainline kernel has support, it is -easier to branch from the -standard kernel and begin development (and not be -concerned with undoing existing changes). This section covers both options. -</para> -<para> -In almost every scenario, the LDAT build system bindings must be completed -before either cloning or starting a new BSP from scratch. This is simply -because the board template files are required to configure a project/build -and create the necessary environment to begin working directly with the -kernel. If it is desired to start immediately with kernel development and -then add LDAT bindings, see the "bootstrapping a BSP" section. -</para> - <section id='creating-from-scratch'> - <title>Creating the BSP from Scratch</title> -<para> -To create the BSP from scratch you need to do the following: -<orderedlist> - <listitem><para>Create a board template for the new BSP in a layer.</para></listitem> - <listitem><para>Configure a build with the board.</para></listitem> - <listitem><para>Configure a kernel.</para></listitem> -</orderedlist> -</para> -<para> -Following is an example showing all three steps. You start by creating a board template for the new BSP in a layer. -<literallayout class='monospaced'> - templates/ - `‐‐ board - `‐‐ my_bsp - |‐‐ include - |‐‐ config.sh - `‐‐ linux - |‐‐ my_bsp.cfg - `‐‐ my_bsp-standard.scc - - > cat config.sh - TARGET_BOARD="my_bsp" - TARGET_LINUX_LINKS="bzImage" - TARGET_SUPPORTED_KERNEL="standard" - TARGET_SUPPORTED_ROOTFS="glibc_std" - BANNER="This BSP is *NOT* supported" - TARGET_PROCFAM="pentium4" - TARGET_PLATFORMS="GPP" - - > cat include - cpu/x86_32_i686 - karch/i386 - - > cat linux/my_bsp-standard.scc - scc_leaf ktypes/standard/standard.scc my_bsp-standard - - > cat linux/my_bsp.cfg - CONFIG_X86=y - CONFIG_SMP=y - CONFIG_VT=y - # etc, etc, etc -</literallayout> -</para> -<para> -Something like the following can now be added to a board build, and -a project can be started: -<literallayout class='monospaced'> - ‐‐enable-board=my_bsp \ - ‐‐with-layer=custom_bsp -</literallayout> -</para> -<para> -Now you can configure a kernel: -<literallayout class='monospaced'> - > make -C build linux.config -</literallayout> -</para> -<para> -You now have a kernel tree, which is branched and has no patches, ready for -development. -</para> - </section> --> - -<!-- <section id='cloning-an-existing-bsp'> - <title>Cloning an Existing BSP</title> -<para> -Cloning an existing BSP from the shipped product is similar to the "from -scratch" option and there are two distinct ways to achieve this goal: -<itemizedlist> - <listitem><para>Create a board template for the new BSP in a layer.</para></listitem> - <listitem><para>Clone the .scc and board config.</para></listitem> -</itemizedlist> -</para> -<para> -The first method is similar to the from scratch BSP where you create a board template for the new -BSP. Although in this case, copying an existing board template from -wrll-wrlinux/templates/board would be appropriate, since we are cloning an -existing BSP. Edit the config.sh, include and other board options for the new -BSP. -</para> -<para> -The second method is to clone the .scc and board config. -To do this, in the newly created board template, create a linux subdirectory and export -the .scc and configuration from the source BSP in the published Yocto Project -kernel. During construction, all of the configuration and patches were -captured, so it is simply a matter of extracting them. -</para> -<para> -Extraction can be accomplished using four different techniques: -<itemizedlist> - <listitem><para>Config and patches from the bare default_kernel.</para></listitem> - <listitem><para>Clone default_kernel and checkout wrs_base.</para></listitem> - <listitem><para>Clone default_kernel and checkout BSP branch.</para></listitem> - <listitem><para>Branch from the Yocto Project BSP.</para></listitem> -</itemizedlist> -</para> -<para> -Technique 1: config and patches from the bare default_kernel -<literallayout class='monospaced'> - > cd layers/wrll-linux-2.6.27/git/default_kernel - > git show checkpoint_end | filterdiff -i '*common_pc*' | patch -s -p2 -d /tmp - - # This will create two directories: cfg and patches. - - > cd /tmp/cfg/kernel-cache/bsp/common_pc/ - - # This directory contains all the patches and .scc files used to construct - # the BSP in the shipped tree. Copy the patches to the new BSP template, - # and add them to the .scc file created above. See "template patching" if - # more details are required. -</literallayout> -</para> -<para> -Technique 2: clone default_kernel and checkout wrs_base -<literallayout class='monospaced'> - > git clone layers/wrll-linux-2.6.27/git/default_kernel windriver-2.6.27 - > cd windriver-2.6.27 - > git checkout wrs_base - > cd wrs/cfg/kernel-cache/bsp/common_pc - -# again, this directory has all the patches and .scc files used to construct -# the BSP -</literallayout> -</para> -<para> -Technique 3: clone default_kernel and checkout BSP branch -<literallayout class='monospaced'> - > git clone layers/wrll-linux-2.6.27/git/default_kernel windriver-2.6.27 - > cd windriver-2.6.27 - > git checkout common_pc-standard - > git whatchanged - # browse patches and determine which ones are of interest, say there are - # 3 patches of interest - > git format-patch -o <path to BSP template>/linux HEAD^^^ - # update the .scc file to add the patches, see "template patches" if - # more details are required -</literallayout> -</para> -<para> -Technique #4: branch from the Yocto Project BSP -<note><para>This is potentially the most "different" technique, but is actually - the easiest to support and leverages the infrastructure. rtcore BSPs - are created in a similar manner to this. -</para></note> -</para> -<para> -In this technique the .scc file in the board template is slightly different - and indicates that the BSP should branch after the base Yocto Project BSP - of the correct kernel type, so to start a new BSP that inherits the - kernel patches of the common_pc-standard, the following would be done: -<literallayout class='monospaced'> - > cat linux/my_bsp-standard.scc - scc_leaf bsp/common_pc/common_pc-standard.scc my_bsp-standard -</literallayout> -</para> -<para> - And only kernel configuration (not patches) need be contained in the - board template. -</para> -<para> - This has the advantage of automatically picking up updates to the BSP - and not duplicating any patches for a similar board. -</para> - </section> --> - - <!-- <section id='bsp-bootstrapping'> - <title>BSP: Bootstrapping</title> -<para> -The previous examples created the board templates and configured a build -before beginning work on a new BSP. It is also possible for advanced users to -simply treat the Yocto Project git repository as an upstream source and begin -BSP development directly on the repository. This is the closest match to how -the kernel community at large would operate. -</para> -<para> -Two techniques exist to accomplish this: -</para> -<para> -Technique 1: upstream workflow -<literallayout class='monospaced'> - > git clone layers/wrll-linux-2.6.27/git/default_kernel windriver-2.6.27 - > cd windriver-2.6.27 - > git checkout -b my_bsp-standard common_pc-standard - - # edit files, import patches, generally do BSP development - - # at this point we can create the BSP template, and export the kernel - # changes using one of the techniques discussed in that section. For - # example, It is possible to push these changes, directly into the - # default_kernel and never directly manipulate or export patch files -</literallayout> -</para> -<para> -Technique 2: Yocto Project kernel build workflow -</para> -<para> - Create the BSP branch from the appropriate kernel type -<literallayout class='monospaced'> - > cd linux - # the naming convention for auto-build is <bsp>-<kernel type> - > git checkout -b my_bsp-standard standard -</literallayout> -</para> -<para> -Make changes, import patches, etc. -<literallayout class='monospaced'> - > ../../host-cross/bin/guilt init - # 'wrs/patches/my_bsp-standard' has now been created to - # manage the branches patches - - # option 1: edit files, guilt import - > ../../host-cross/bin/guilt new extra-version.patch - > vi Makefile - > ../../host-cross/bin/guilt refresh - # add a header - > ../../host-cross/bin/guilt header -e - # describe the patch using best practices, like the example below: - - ‐‐‐>‐‐‐>‐‐‐> cut here - From: Bruce Ashfield <bruce.ashfield@windriver.com> - - Adds an extra version to the kernel - - Modify the main EXTRAVERSION to show our bsp name - - Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com> - ‐‐‐>‐‐‐>‐‐‐> cut here - - # option 2: import patches - > git am <patch> - or - > git apply <patch> - > git add <files> - > git commit -s - - # configure the board, save relevant options - > make ARCH=<arch> menuconfig - - # save the cfg changes for reconfiguration - > mkdir wrs/cfg/<cache>/my_bsp - > vi wrs/cfg/<cache>/my_bsp/my_bsp.cfg - - # classify the patches - > ../../host-cross/bin/kgit classify create <kernel-foo-cache>/my_bsp/my_bsp - # test build - > cd .. - > make linux TARGET_BOARD=my_bsp kprofile=my_bsp use_current_branch=1 -</literallayout> -</para> -<para> - Assuming the patches have been exported to the correct location, Future - builds will now find the board, apply the patches to the base tree and make - the relevant branches and structures and the special build options are no - longer required. -</para> - </section> - </section> --> - -<!-- <section id='patching'> - <title>Patching</title> -<para> -The most common way to apply patches to the kernel is via a template. -However, for more advanced applications (such as the sharing of patches between -multiple sub-features) it is possible to patch the kernel-cache. -This section covers both scenarios. -</para> - <section id='patching-template'> - <title>Patching: Template</title> -<para> -kernel -templates follow the same rules as any LDAT template. A directory should be -created in a recognized template location, with a 'linux' subdirectory. The -'linux' directory triggers LDAT to pass the dir as a potential patch location -to the kernel build system. Any .scc files found in that directory, will be -automatically appended to the end of the BSP branch (for the configured -board). -</para> -<para> -This behavior is essentially the same since previous product -releases. The only exception is the use of ".scc", which allows kernel -configuration AND patches to be applied in a template. -</para> -<note><para> -If creating a full template is not required, a .scc file can be placed at -the top of the build, along with configuration and patches. The build -system will pickup the .scc and add it onto the patch list automatically -</para></note> -<para> -As an example, consider a simple template to update a BP: -<literallayout class='monospaced'> - > cat templates/feature/extra_version/linux/extra_version.scc - patch 0001-extraversion-add-Wind-River-identifier.patch -</literallayout> -</para> -<para> -To illustrate how the previous template patch was created, the following -steps were performed: -<literallayout class='monospaced'> - > cd <board build>/build/linux - > vi Makefile - # modify EXTRAVERSION to have a unique string - > git commit -s -m "extraversion: add Yocto Project identifier" Makefile - > git format-patch -o <path to layer>/templates/feature/extra_version/linux/ - > echo "patch 0001-extraversion-add-Wind-River-identifier.patch" > \ - <path to layer>/templates/feature/extra_version/linux/extra_version.scc -</literallayout> -</para> -<para> -This next example creates a template with a linux subdirectory, just as we - always have for previous releases. -<literallayout class='monospaced'> - > mkdir templates/features/my_feature/linux -</literallayout> -</para> -<para> - In that directory place your feature description, your - patch and configuration (if required). -<literallayout class='monospaced'> - > ls templates/features/my_feature/linux - - version.patch - my_feature.scc - my_feature.cfg -</literallayout> -</para> -<para> - The .scc file describes the patches, configuration and - where in the patch order the feature should be inserted. -<literallayout class='monospaced'> - patch version.patch - kconf non-hardware my_feature.cfg -</literallayout> -</para> -<para> - Configure your build with the new template -<literallayout class='monospaced'> - ‐‐with-template=features/my_feature -</literallayout> -</para> -<para> -Build the kernel -<literallayout class='monospaced'> - > make linux -</literallayout> -</para> - </section> - - <section id='patching-kernel-cache'> - <title>Patching: Kernel Cache</title> -<para> -As previously mentioned, this example is included for completeness, and is for more advanced -applications (such as the sharing of patches between multiple sub-features). -Most patching should be done via templates, since that interface is -guaranteed not to change and the kernel-cache interface carries no such -guarantee. -</para> -<para> -At the top of a layer, create a kernel cache. The build system will recognize -any directory of the name 'kernel-*-cache' as a kernel cache. -<literallayout class='monospaced'> - > cd <my layer> - >mkdir kernel-temp-cache -</literallayout> -</para> -<para> -Make a directory with the BSP -<literallayout class='monospaced'> - > mkdir kernel-temp-cache - > mkdir kernel-temp-cache/my_feat -</literallayout> -</para> -<para> -Create the feature files as they were in technique #1 -<literallayout class='monospaced'> - > echo "patch my_patch.path" > kernel-temp-cache/my_feat/my_feature.scc -</literallayout> -</para> -<para> -Configure the build with the feature added to the kernel type -<literallayout class='monospaced'> - ‐‐with-kernel=standard+my_feat/my_feature.scc -</literallayout> -</para> -<para> -Build the kernel -<literallayout class='monospaced'> - > make linux -</literallayout> -</para> - </section> - </section> - - <section id='bsp-updating-patches-and-configuration'> - <title>BSP: Updating Patches and Configuration</title> -<para> -As was described in the "template patching" example, it is simple -to add patches to a BSP via a template, but often, it is desirable -to experiment and test patches before committing them to a template. -You can do this by modifying the BSP source. -</para> -<para> -Start as follows: -<literallayout class='monospaced'> - > cd linux - > git checkout <bspname>-<kernel name> - - > git am <patch> -</literallayout> -</para> -<para> -Or you can do this: -<literallayout class='monospaced'> - > kgit-import -t patch <patch> - - > cd .. - > make linux -</literallayout> -</para> -<para> -For details on conflict resolution and patch application, see the -git manual, or other suitable online references. -<literallayout class='monospaced'> - > git am <mbox> - # conflict - > git apply ‐‐reject .git/rebase-apply/0001 - # resolve conflict - > git am ‐‐resolved (or git am ‐‐skip, git am ‐‐abort) - # continue until complete -</literallayout> -</para> -<para> -Here is another example: -<literallayout class='monospaced'> - # merge the patches - # 1) single patch - > git am <mbox> - > git apply <patch< - > kgit import -t patch <patch> - - # 2) multiple patches - > git am <mbox> - > kgit import -t dir <dir> - - # if kgit -t dir is used, a patch resolution cycle such - # as this can be used: - - > kgit import -t dir <dir> - # locate rejects and resolve - # options: - > wiggle ‐‐replace <path to file> <path to reject> - > guilt refresh - or - > # manual resolution - > git add <files> - > git commit -s - or - > git apply ‐‐reject .git/rebase-apply/0001 - > git add <files> - > git am ‐‐resolved - or - > # merge tool of choice - - # continue series: - - > kgit import -t dir <dir> - or - > git am ‐‐continue -</literallayout> -</para> -<para> -Once all the patches have been tested and are satisfactory, they -should be exported via the techniques described in "saving kernel -modifications." -</para> -<para> -Once the kernel has been patched and configured for a BSP, it's -configuration commonly needs to be modified. This can be done by -running [menu|x]config on the kernel tree, or working with -configuration fragments. -</para> -<para> -Using menuconfig, the operation is as follows: -<literallayout class='monospaced'> - > make linux.menuconfig - > make linux.rebuild -</literallayout> -</para> -<para> -Once complete, the changes are in linux-<bsp>-<kernel type>-build/.config. -To permanently save these changes, compare the .config before and after the -menuconfig, and place those changes in a configuration fragment in the -template of your choice. -</para> -<para> -Using configuration fragments, the operation is as follows (using the -si_is8620 as an example BSP): -<literallayout class='monospaced'> - > vi linux/wrs/cfg/kernel-cache/bsp/si_is8620/si_is8620.cfg - > make linux.reconfig - > make linux.rebuild -</literallayout> -</para> -<para> -The modified configuration fragment can simply be copied out of the -linux/wrs/.. directory and placed in the appropriate template for future -application. -</para> - </section> - - <section id='tools-guilt'> - <title>Tools: guilt</title> -<para> -Yocto Project has guilt integrated as a kernel tool; therefore users that are -familiar with quilt may wish to use this tool to pop, push and refresh -their patches. Note: guilt should only be used for local operations, once -a set of changes has been pushed or pulled, they should no longer be popped -or refresh by guilt, since popping, refreshing and re-pushing patches -changes their commit IDs and creating non-fast forward branches. -</para> -<para> -The following example illustrates how to add patches a Yocto Project -BSP branch via guilt: -<literallayout class='monospaced'> - > cd build/linux - > git checkout common_pc-standard - > guilt new extra.patch - # edit files, make changes, etc - > guilt refresh - > guilt top - extra.patch - - # export that patch to an external location - > kgit export -p top /tmp -</literallayout> -</para> -<para> -Other guilt operations of interest are: -<literallayout class='monospaced'> - > guilt push, guilt push -a - > guilt pop - > guilt applied, guilt unapplied - > guilt top - > guilt refresh - > guilt header -e - > guilt next -</literallayout> -</para> -<note><para> -Guilt only uses git commands and git plumbing to perform its operations, -anything that guilt does can also be done using git directly. It is provided -as a convenience utility, but is not required and the developer can use whatever -tools or workflow they wish. -</para></note> -<para> -The following builds from the above instructions to show how guilt can be -used to assist in getting your BSP kernel patches ready. You should follow -the above instructions up to and including 'make linux.config'. In this -example I will create a new commit (patch) from scratch and import another -fictitious patch from some external public git tree (ie, a commit with full -message, signoff etc.). Please ensure you have host-cross/bin in your path. -<literallayout class='monospaced'> - %> cd linux - %> guilt-init - %> guilt-new -m fill_me_in_please first_one.patch - %> touch somefile.txt - %> guilt-add somefile.txt - %> guilt-header -e - %> guilt-refresh - %> guilt-import path_to_some_patch/patch_filename - %> guilt-push -</literallayout> -</para> -<para> -Here are a few notes about the above: -<itemizedlist> - <listitem><para>guilt-header -e ‐‐ this will open editing of the patch header in - EDITOR. As with a git commit the first line is the short log and - should be just that short and concise message about the commit. Follow - the short log with lines of text that will be the long description but - note Do not put a blank line after the short log. As usual you will - want to follow this with a blank line and then a signoff line.</para></listitem> - - <listitem><para>The last line in the example above has 2 dots on the end. If you - don't add the 2 periods on the end guilt will think you are sending - just one patch. The wrong one!</para></listitem> - - <listitem><para>The advantage to using guilt over not using guilt is that if you have a - review comment in the first patch (first_one.patch in the case of this - example) it is very easy to use guilt to pop the other patches off - allowing you to make the necessary changes without having to use more - inventive git type strategies.</para></listitem> -</itemizedlist> -</para> - </section> - - <section id='tools-scc-file-example'> - <title>Tools: scc File Example</title> -<para> -This section provides some scc file examples: leaf node, 'normal' mode, and transforms. -</para> - <section id='leaf-node'> - <title>Leaf Node</title> -<para> -The following example is a BSP branch with no child branches - a leaf on the tree. -<literallayout class='monospaced'> - # these are optional, but allow standalone tree construction - define WRS_BOARD <name> - define WRS_KERNEL <kern type> - define WRS_ARCH <arch> - - scc_leaf ktypes/standard common_pc-standard - # ^ ^ - # +‐‐ parent + branch name - - include common_pc.scc - # ^ - # +‐‐‐ include another feature -</literallayout> -</para> - </section> - - <section id='normal-mode'> - <title>'Normal' Mode</title> -<para> -Here is an example of 'normal' mode: -<literallayout class='monospaced'> - # +‐‐‐‐ name of file to read - # v - kconf hardware common_pc.cfg - # ^ ^ - # | +‐‐ 'type: hardware or non-hardware - # | - # +‐‐‐ kernel config - - # patches - patch 0002-atl2-add-atl2-driver.patch - patch 0003-net-remove-LLTX-in-atl2-driver.patch - patch 0004-net-add-net-poll-support-for-atl2-driver.patch -</literallayout> -</para> - - </section> - - <section id='transforms'> - <title>Transforms</title> -<para> -This section shows an example of transforms: -<literallayout class='monospaced'> - # either of the next two options will trigger an 'auto' - # branch from existing ones, since they change the commit - # order and hence must construct their own branch - - # this changes the order of future includes, if the - # passed feature is detected, the first feature is - # included AFTER it - include features/rt/rt.scc after features/kgdb/kgdb - # this also changes the order of existing branches - # this prevents the named feature from ever being - # included - exclude features/dynamic_ftrace/dynamic_ftrace.scc - - # inherit the standard kernel - include ktypes/standard/standard - - - # LTT supplies this, so we don't want the sub-chunk from RT. - patch_trigger arch:all exclude ftrace-upstream-tracepoints.patch - # ...but we still want the one unique tracepoint it added. - patch tracepoint-add-for-sched_resched_task.patch - - # these will change the named patches in the series into - # <patch name>.patch.<feature name> - # where the substituted patch is in this directory - patch_trigger arch:all ctx_mod dynamic_printk.patch - patch_trigger arch:all ctx_mod 0001-Implement-futex-macros-for-ARM.patch - # unconditionally exclude a patch - patch_trigger arch:all exclude ftrace-fix-ARM-crash.patch -</literallayout> -</para> - </section> - </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 there are modification in the source -directory that haven't been committed. -<literallayout class='monospaced'> - > git status -</literallayout> -</para> -<para> -The above git command will indicate modified, removed or added files. Those changes should -be committed to the tree (even if they will never be saved, or exported -for future use) and the kernel rebuilt. -</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> -And then rebuild the kernel -</para> - </section> - - <section id='kernel-transition-kernel-layer'> - <title>Kernel: Transition Kernel Layer</title> -<para> -In order to temporarily use a different base kernel in Yocto Project -Linux 3.0 you need to do the following: -<orderedlist> - <listitem><para>Create a custom kernel layer.</para></listitem> - <listitem><para>Create a git repository of the transition kernel.</para></listitem> -</orderedlist> -</para> -<para> -Once those requirements are met multiple boards and kernels can -be built. The cost of setup is only paid once and then additional -BSPs and options can be added. -</para> -<para> -This creates a transition kernel layer to evaluate functionality -of some other kernel with the goal of easing transition to an -integrated and validated Yocto Project kernel. -</para> -<!--<para> -The next few sections describe the process: -</para> --> - <!-- <section id='creating-a-custom-kernel-layer'> - <title>Creating a Custom Kernel Layer</title> -<para> -The custom kernel layer must have the following minimum -elements: -<itemizedlist> - <listitem><para>An include of the shipped Yocto Project kernel layer.</para></listitem> - <listitem><para>A kernel-cache with an override of the standard kernel type.</para></listitem> -</itemizedlist> -</para> -<para> -This allows the inheritance of the kernel build infrastructure, -while overriding the list of patches that should be applied to -the base kernel. -</para> -<para> -The kernel layer can optionally include an override to the base -Yocto Project Linux BSP to inhibit the application of BSP specific -patches. If a custom BSP is being used, this is not required. -</para> - </section> --> - - <!-- <section id='git-repo-of-the-transition-kernel'> - <title>git Repo of the Transition Kernel</title> -<para> -The kernel build system requires a base kernel repository to -seed the build process. This repository must be found in the -same layer as the build infrastructure (i.e wrll-linux-2.6.27) -in the 'git' subdir, with the name 'default_kernel' -</para> -<para>Since Yocto Project Linux ships with a default_kernel -(the validated Yocto Project kernel) in the wrll-linux-2.6.27 -kernel layer, that must be removed and replaced with the -transition kernel. -</para> -<para>If the Yocto Project install cannot be directly modified -with the new default kernel, then the path to the transition -kernel layer's 'git' subdir must be passed to the build -process via: -<programlisting> -linux_GIT_BASE=<absolute path to layer>/git -</programlisting> -</para> -<para> -If the transition kernel has not been delivered via git, -then a git repo should be created, and bare cloned into -place. Creating this repository is as simple as: -<literallayout class='monospaced'> - > tar zxvf temp_kernel.tgz - > cd temp_kernel - > git init - > git add . - > git commit -a -m "Transition kernel baseline" - - 'temp_kernel' can now be cloned into place via: - - > cd <path to git base>/git - > git clone ‐‐bare <path to temp_kernel/temp_kernel default_kernel -</literallayout> -</para> - </section> --> - - <!-- <section id='building-the-kernel'> - <title>Building the Kernel</title> -<para> -Once these prerequisites have been met, the kernel can be -built with: -<literallayout class='monospaced'> - > make linux -</literallayout> -</para> -<para> -The new base kernel will be cloned into place and have any patches -indicated in the transition kernel's cache (or templates) applied. -The kernel build will detect the non-Yocto Project base repo and -use the HEAD of the tree for the build. -</para> - </section> --> - - <!-- <section id='example'> - <title>Example</title> -<para> -This example creates a kernel layer to build the latest -kernel.org tree as the 'common_pc' BSP. -<literallayout class='monospaced'> - > cd <path to layers> - > mkdir wrll-linux-my_version - > cd wrll-linux-my_version - > echo "wrll-linux-2.6.27" > include - > mkdir -p kernel-cache/ktypes/standard - > mkdir -p kernel-cache/bsp/common_pc - > echo "v2.6.29" > kernel-cache/kver - > echo "branch common_pc-standard" > kernel-cache/bsp/common_pc/common_pc.scc - > echo "kconf hardware common_pc.cfg" >> kernel-cache/bsp/common_pc/common_pc.scc - > echo "CONFIG_FOO=y" > kernel-cache/bsp/common_pc/common_pc.cfg - > mkdir git - > cd git - > git clone ‐‐bare git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git default_kernel -</literallayout> -</para> -<para> -Configure a build to use the new layer. This means that: -<literallayout class='monospaced'> - ‐‐enable-kernel-version=my_version -</literallayout> -</para> -<para> -Should be used to override the shipped default. -</para> -<para> -To build the kernel: -<literallayout class='monospaced'> - > cd build - > make linux_GIT_BASE=<layer path>/wrll-linux-my_version/git linux -</literallayout> -</para> -<para> -If this is to build without some user intervention (passing of the -GIT_BASE), you must do the clone into the wrll-linux-2.6.27/git directory. -</para> -<note><para>Unless you define valid "hardware.kcf" and "non-hardware.kcf" some -non fatal warnings will be seen. They can be fixed by populating these -files in the kernel-cache with valid hardware and non hardware config -options. -</para></note> - </section> --> - </section> - </section> - - - - - -<!-- <itemizedlist> - <listitem><para>Introduction to this section.</para></listitem> - <listitem><para>Constructing a project-specific kernel tree.</para></listitem> - <listitem><para>Building the kernel.</para></listitem> - <listitem><para>Seeing what has changed.</para></listitem> - <listitem><para>Seeing what has changed in a particular branch.</para></listitem> - <listitem><para>Modifying the kernel.</para></listitem> - <listitem><para>Saving modifications.</para></listitem> - <listitem><para>Storing patches outside of the kernel source repository (bulk export).</para></listitem> - <listitem><para>Working with incremental changes.</para></listitem> - <listitem><para>Extracting commited changes from a working directory (exporting internally through - patches.</para></listitem> - <listitem><para>Pushing commited changes.</para></listitem> - <listitem><para>Exporting for external (upstream) submission.</para></listitem> - <listitem><para>Exporting for import into another Source Control Manager (SCM).</para></listitem> - <listitem><para>Working with the Yocto Project kernel in another SCM.</para> - <itemizedlist> - <listitem><para>Exporting the delivered kernel to an SCM.</para></listitem> - <listitem><para>Importing changed for the build.</para></listitem> - </itemizedlist></listitem> - <listitem><para>Migrating templates from version 2.0.</para></listitem> - <listitem><para>Creating a new Board Support Package (BSP).</para> - <itemizedlist> - <listitem><para>Creating from scratch.</para></listitem> - <listitem><para>Cloning.</para></listitem> - </itemizedlist></listitem> - <listitem><para>BSP bootstrapping.</para></listitem> - <listitem><para>Applying patches to the kernel through a template.</para></listitem> - <listitem><para>Applying patches to the kernel without using a template.</para></listitem> - <listitem><para>Updating patches and configurations for a BSP.</para></listitem> - <listitem><para>Using guilt to add and export patches.</para></listitem> - <listitem><para>Using scc.</para></listitem> - <listitem><para>Building a 'dirty' image.</para></listitem> - <listitem><para>Temporarily using a different base kernel.</para></listitem> - <listitem><para>Creating a custom kernel layer.</para></listitem> - <listitem><para>Creating the git repository of the transition kernel.</para></listitem> - </itemizedlist> --> - - -</section> - -</chapter> -<!-- -vim: expandtab tw=80 ts=4 ---> |