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authorScott Rifenbark <scott.m.rifenbark@intel.com>2010-11-24 08:39:54 -0800
committerSaul Wold <Saul.Wold@intel.com>2010-12-10 22:01:09 -0800
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documentation/kernel-manual/yocto-project-kernal-manual.xml: and yocto-project-kernal-manual-customization.xsl removed from tree.
I noticed I had mis-spelled kernel for these files names after committing the new kernel manual. I renamed the files and had to remove these two. Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
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-<?xml version='1.0'?>
-<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml" xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0">
-
- <xsl:import href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl" />
-
- <xsl:param name="generate.toc" select="'article nop'"></xsl:param>
-
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diff --git a/documentation/kernel-manual/yocto-project-kernal-manual.xml b/documentation/kernel-manual/yocto-project-kernal-manual.xml
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-<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
-"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<article id='intro'>
- <imagedata fileref="figures/yocto-project-transp.png" width="6in" depth="1in" align="right" scale="25" />
-
-<section id='fake-title'>
- <title>Yocto Project Kernel Architecture and Use Manual</title>
-</section>
-
-<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="4in" 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="4in" 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 &amp; 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 &amp; 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 staff 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>configured and default templates</para></listitem>
- </itemizedlist>
-
- <para>In a typical build a feature description of the format:
- &lt;bsp name&gt;-&lt;kernel type&gt;.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 command line, the configure script or
- templates.</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 (normally kernel.org) 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 &lt;bsp name&gt;-&lt;kernel type&gt;.</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 &lt;bsp name&gt;-&lt;kernel type&gt;.</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-&lt;BSPname&gt;-&lt;kerntype&gt;-build" where
-kerntype is one of standard, cg``
-e, etc. 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 &amp; 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 &lt;relative path&gt;/&lt;patch name&gt;: 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 &gt;condition&lt; &gt;action&lt; &lt;tgt&gt;: indicate that a trigger should be set to perform an action on a
- patch.</para>
-
-<para>The conditions can be:
-
- <itemizedlist>
- <listitem><para>arch:&lt;comma separated arch list or "all"&gt;</para></listitem>
- <listitem><para>plat:&lt;comma separated platform list or "all"&gt;</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 &lt;feature name&gt; [after &lt;feature&gt;]: 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 &lt;path&gt; and
- is transparent to the feature script. This means that &lt;feature name&gt; 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 &lt;feature name&gt;: 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 &lt;command&gt;: 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 &lt;directory&gt;: 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 &lt;type&gt; &lt;fragment name&gt;: associates a kernel config frag with the feature.
- &lt;type&gt; can be
- "hardware" or "non-hardware" and is used by the kernel configuration
- subsystem to audit configuration. &lt;fragment name&gt; 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 &lt;branch name&gt;: 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 &lt;base feature&gt; &lt;branch name&gt;: 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 &lt;tag name&gt;: 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 &lt;var&gt; &lt;value&gt;: 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 previous Yocto Project releases, there were 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 (&lt;kernel type&gt;..&lt;bsp&gt;-&lt;kernel type&gt;), kernel.org history is blended
-with Yocto Project changes
-</para>
-<literallayout class='monospaced'>
- # full description of the changes
- &gt; git whatchanged &lt;kernel type&gt;..&lt;bsp&gt;-&lt;kernel type&gt;
- &gt; eg: git whatchanged standard..common_pc-standard
-
- # summary of the changes
- &gt; git log &dash;&dash;pretty=oneline &dash;&dash;abbrev-commit &lt;kernel type&gt;..&lt;bsp&gt;-&lt;kernel type&gt;
-
- # source code changes (one combined diff)
- &gt; git diff &lt;kernel type&gt;..&lt;bsp&gt;-&lt;kernel type&gt;
- &gt; git show &lt;kernel type&gt;..&lt;bsp&gt;-&lt;kernel type&gt;
-
- # dump individual patches per commit
- &gt; git format-patch -o &lt;dir&gt; &lt;kernel type&gt;..&lt;bsp&gt;-&lt;kernel type&gt;
-
- # determine the change history of a particular file
- &gt; git whatchanged &lt;path to file&gt;
-
- # determine the commits which touch each line in a file
- &gt; git blame &lt;path to file&gt;
-</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
- &gt; git show &lt;tag&gt;
- &gt; eg: git show yaffs2
-
- # determine which branches contain a feature
- &gt; git branch &dash;&dash;contains &lt;tag&gt;
-
- # show the changes in a kernel type
- &gt; git whatchanged wrs_base..&lt;kernel type&gt;
- &gt; 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
-
- &gt; git add .
- &gt; git commit -s -a -m &gt;commit message&lt;
- or
- &gt; 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
- &gt; vi &gt;path&lt;/file
- # stage the change
- &gt; git add &gt;path&lt;/file
- # commit the change
- &gt; git commit -s
- # remove a file
- &gt; git rm &gt;path&lt;/file
- # commit the change
- &gt; 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'>
- &gt; git add &gt;path&lt;/file
- &gt; git commit &dash;&dash;amend
- &gt; 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
- &gt; git reset &dash;&dash;hard HEAD^
- # remove the commit, but leave the files changed and staged for re-commit
- &gt; git reset &dash;&dash;soft HEAD^
- # remove the commit, leave file change, but not staged for commit
- &gt; git reset &dash;&dash;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'>
- # &gt;first commit&gt; 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.
-
- &gt; git format-patch -o &lt;dir&gt; &lt;first commit&gt;..&lt;last commit&gt;
-</literallayout>
-</para>
-
-<para>
- In other words:
-<literallayout class='monospaced'>
- # identify commits of interest.
-
- # if the tree was tagged before development
- &gt; git format-patch -o &lt;save dir&gt; &lt;tag&gt;
-
- # if no tags are available
- &gt; git format-patch -o &lt;save dir&gt; HEAD^ # last commit
- &gt; git format-patch -o &lt;save dir&gt; HEAD^^ # last 2 commits
- &gt; git whatchanged # identify last commit
- &gt; git format-patch -o &lt;save dir&gt; &lt;commit id&gt;
- &gt; git format-patch -o &lt;save dir&gt; &lt;rev-list&gt;
-</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://&lt;master server&gt;/&lt;path to repo&gt; &lt;local branch&gt;:&lt;remote branch&gt;
-</literallayout>
-For example:
-<literallayout class='monospaced'>
- &gt; push ssh://openlinux.windriver.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
- &gt; git format-patch &dash;&dash;thread -n -o ~/rr/ HEAD^^^^
- &gt; git send-email &dash;&dash;compose &dash;&dash;subject '[RFC 0/N] &lt;patch series summary&gt;' \
- &dash;&dash;to foo@yoctoproject.org &dash;&dash;to bar@yoctoproject.org \
- &dash;&dash;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'>
- &gt; git checkout common_pc-standard
- &gt; cd .. ; echo linux/.git &gt; .cvsignore
- &gt; 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'>
- &gt; git checkout common_pc-standard
- &gt; git merge cav_ebt5800-standard
- # resolve any conflicts and commit them
- &gt; cd .. ; echo linux/.git &gt; .cvsignore
- &gt; 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>
-If changes are exported as patches, they can be placed in a template and
-automatically applied to the kernel during patching. See the template patch
-example for details.
-<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>
-The following example illustrates one variant of this workflow:
-<literallayout class='monospaced'>
- # on master git repository
- &gt; cd linux-2.6.27
- &gt; git tag -d common_pc-standard-mark
- &gt; git pull ssh://&lt;foo&gt;@&lt;bar&gt;/pub/git/kernel-2.6.27 common_pc-standard:common_pc-standard
- &gt; git tag common_pc-standard-mark
-
- # on each build machine (or NFS share, etc)
- &gt; cd wrll-linux-2.6.27/git/default_kernel
- &gt; git fetch ssh://&lt;foo&gt;@&lt;master server&gt;/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.
- &gt; 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/
- `&dash;&dash; board
- `&dash;&dash; my_board
- |&dash;&dash; config.sh
- |&dash;&dash; include
- `&dash;&dash; linux
- `&dash;&dash; 2.6.x
- |&dash;&dash; knl-base.cfg
- |&dash;&dash; bsp.patch
- `&dash;&dash; my_bsp.smudge
-
- &gt; mv templates/board/my_board/linux/2.6.x/* templates/board/my_board/linux
- &gt; rm -rf templates/board/my_board/linux/2.6.x/
- &gt; mv templates/board/my_board/linux/my_bsp.smudge \
- templates/board/my_board/linux/my_bsp-standard.scc
- &gt; echo "kconf hardware knl-base.cfg" &gt;&gt; \
- templates/board/my_board/linux/my_bsp-standard.scc
- &gt; 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/
- `&dash;&dash; board
- `&dash;&dash; my_board
- |&dash;&dash; config.sh
- |&dash;&dash; include
- `&dash;&dash; linux
- |&dash;&dash; knl-base.cfg
- |&dash;&dash; bsp.patch
- `&dash;&dash; 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'>
- &lt;bsp name&gt;-&lt;kernel type&gt;.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-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/
- `&dash;&dash; board
- `&dash;&dash; my_bsp
- |&dash;&dash; include
- |&dash;&dash; config.sh
- `&dash;&dash; linux
- |&dash;&dash; my_bsp.cfg
- `&dash;&dash; my_bsp-standard.scc
-
- &gt; 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"
-
- &gt; cat include
- cpu/x86_32_i686
- karch/i386
-
- &gt; cat linux/my_bsp-standard.scc
- scc_leaf ktypes/standard/standard.scc my_bsp-standard
-
- &gt; 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'>
- &dash;&dash;enable-board=my_bsp \
- &dash;&dash;with-layer=custom_bsp
-</literallayout>
-</para>
-<para>
-Now you can configure a kernel:
-<literallayout class='monospaced'>
- &gt; 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'>
- &gt; cd layers/wrll-linux-2.6.27/git/default_kernel
- &gt; git show checkpoint_end | filterdiff -i '*common_pc*' | patch -s -p2 -d /tmp
-
- # This will create two directories: cfg and patches.
-
- &gt; 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'>
- &gt; git clone layers/wrll-linux-2.6.27/git/default_kernel windriver-2.6.27
- &gt; cd windriver-2.6.27
- &gt; git checkout wrs_base
- &gt; 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'>
- &gt; git clone layers/wrll-linux-2.6.27/git/default_kernel windriver-2.6.27
- &gt; cd windriver-2.6.27
- &gt; git checkout common_pc-standard
- &gt; git whatchanged
- # browse patches and determine which ones are of interest, say there are
- # 3 patches of interest
- &gt; git format-patch -o &lt;path to BSP template&gt;/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'>
- &gt; 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'>
- &gt; git clone layers/wrll-linux-2.6.27/git/default_kernel windriver-2.6.27
- &gt; cd windriver-2.6.27
- &gt; 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'>
- &gt; cd linux
- # the naming convention for auto-build is &lt;bsp&gt;-&lt;kernel type&gt;
- &gt; git checkout -b my_bsp-standard standard
-</literallayout>
-</para>
-<para>
-Make changes, import patches, etc.
-<literallayout class='monospaced'>
- &gt; ../../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
- &gt; ../../host-cross/bin/guilt new extra-version.patch
- &gt; vi Makefile
- &gt; ../../host-cross/bin/guilt refresh
- # add a header
- &gt; ../../host-cross/bin/guilt header -e
- # describe the patch using best practices, like the example below:
-
- &dash;&dash;&dash;&gt;&dash;&dash;&dash;&gt;&dash;&dash;&dash;&gt; cut here
- From: Bruce Ashfield &lt;bruce.ashfield@windriver.com&gt;
-
- Adds an extra version to the kernel
-
- Modify the main EXTRAVERSION to show our bsp name
-
- Signed-off-by: Bruce Ashfield &lt;bruce.ashfield@windriver.com&gt;
- &dash;&dash;&dash;&gt;&dash;&dash;&dash;&gt;&dash;&dash;&dash;&gt; cut here
-
- # option 2: import patches
- &gt; git am &lt;patch&gt;
- or
- &gt; git apply &lt;patch&gt;
- &gt; git add &lt;files&gt;
- &gt; git commit -s
-
- # configure the board, save relevant options
- &gt; make ARCH=&lt;arch&gt; menuconfig
-
- # save the cfg changes for reconfiguration
- &gt; mkdir wrs/cfg/&lt;cache&gt;/my_bsp
- &gt; vi wrs/cfg/&lt;cache&gt;/my_bsp/my_bsp.cfg
-
- # classify the patches
- &gt; ../../host-cross/bin/kgit classify create &lt;kernel-foo-cache&gt;/my_bsp/my_bsp
- # test build
- &gt; cd ..
- &gt; 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'>
- &gt; 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'>
- &gt; cd &lt;board build&gt;/build/linux
- &gt; vi Makefile
- # modify EXTRAVERSION to have a unique string
- &gt; git commit -s -m "extraversion: add Yocto Project identifier" Makefile
- &gt; git format-patch -o &lt;path to layer&gt;/templates/feature/extra_version/linux/
- &gt; echo "patch 0001-extraversion-add-Wind-River-identifier.patch" &gt; \
- &lt;path to layer&gt;/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'>
- &gt; 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'>
- &gt; 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'>
- &dash;&dash;with-template=features/my_feature
-</literallayout>
-</para>
-<para>
-Build the kernel
-<literallayout class='monospaced'>
- &gt; 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'>
- &gt; cd &lt;my layer&gt;
- &gt;mkdir kernel-temp-cache
-</literallayout>
-</para>
-<para>
-Make a directory with the BSP
-<literallayout class='monospaced'>
- &gt; mkdir kernel-temp-cache
- &gt; mkdir kernel-temp-cache/my_feat
-</literallayout>
-</para>
-<para>
-Create the feature files as they were in technique #1
-<literallayout class='monospaced'>
- &gt; echo "patch my_patch.path" &gt; 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'>
- &dash;&dash;with-kernel=standard+my_feat/my_feature.scc
-</literallayout>
-</para>
-<para>
-Build the kernel
-<literallayout class='monospaced'>
- &gt; 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'>
- &gt; cd linux
- &gt; git checkout &lt;bspname&gt;-&lt;kernel name&gt;
-
- &gt; git am &lt;patch&gt;
-</literallayout>
-</para>
-<para>
-Or you can do this:
-<literallayout class='monospaced'>
- &gt; kgit-import -t patch &lt;patch&gt;
-
- &gt; cd ..
- &gt; 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'>
- &gt; git am &lt;mbox&gt;
- # conflict
- &gt; git apply &dash;&dash;reject .git/rebase-apply/0001
- # resolve conflict
- &gt; git am &dash;&dash;resolved (or git am &dash;&dash;skip, git am &dash;&dash;abort)
- # continue until complete
-</literallayout>
-</para>
-<para>
-Here is another example:
-<literallayout class='monospaced'>
- # merge the patches
- # 1) single patch
- &gt; git am &lt;mbox&gt;
- &gt; git apply &lt;patch&lt;
- &gt; kgit import -t patch &lt;patch&gt;
-
- # 2) multiple patches
- &gt; git am &lt;mbox&gt;
- &gt; kgit import -t dir &lt;dir&gt;
-
- # if kgit -t dir is used, a patch resolution cycle such
- # as this can be used:
-
- &gt; kgit import -t dir &lt;dir&gt;
- # locate rejects and resolve
- # options:
- &gt; wiggle &dash;&dash;replace &lt;path to file&gt; &lt;path to reject&gt;
- &gt; guilt refresh
- or
- &gt; # manual resolution
- &gt; git add &lt;files&gt;
- &gt; git commit -s
- or
- &gt; git apply &dash;&dash;reject .git/rebase-apply/0001
- &gt; git add &lt;files&gt;
- &gt; git am &dash;&dash;resolved
- or
- &gt; # merge tool of choice
-
- # continue series:
-
- &gt; kgit import -t dir &lt;dir&gt;
- or
- &gt; git am &dash;&dash;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'>
- &gt; make linux.menuconfig
- &gt; make linux.rebuild
-</literallayout>
-</para>
-<para>
-Once complete, the changes are in linux-&lt;bsp&gt;-&lt;kernel type&gt;-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'>
- &gt; vi linux/wrs/cfg/kernel-cache/bsp/si_is8620/si_is8620.cfg
- &gt; make linux.reconfig
- &gt; 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'>
- &gt; cd build/linux
- &gt; git checkout common_pc-standard
- &gt; guilt new extra.patch
- # edit files, make changes, etc
- &gt; guilt refresh
- &gt; guilt top
- extra.patch
-
- # export that patch to an external location
- &gt; 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 &dash;&dash; 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 &lt;name&gt;
- define WRS_KERNEL &lt;kern type&gt;
- define WRS_ARCH &lt;arch&gt;
-
- scc_leaf ktypes/standard common_pc-standard
- # ^ ^
- # +&dash;&dash; parent + branch name
-
- include common_pc.scc
- # ^
- # +&dash;&dash;&dash; 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'>
- # +&dash;&dash;&dash;&dash; name of file to read
- # v
- kconf hardware common_pc.cfg
- # ^ ^
- # | +&dash;&dash; 'type: hardware or non-hardware
- # |
- # +&dash;&dash;&dash; 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
- # &lt;patch name&gt;.patch.&lt;feature name&gt;
- # 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'>
- &gt; 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'>
- &gt; git add .
- &gt; 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=&lt;absolute path to layer&gt;/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'>
- &gt; tar zxvf temp_kernel.tgz
- &gt; cd temp_kernel
- &gt; git init
- &gt; git add .
- &gt; git commit -a -m "Transition kernel baseline"
-
- 'temp_kernel' can now be cloned into place via:
-
- &gt; cd &lt;path to git base&gt;/git
- &gt; git clone &dash;&dash;bare &lt;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'>
- &gt; 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'>
- &gt; cd &lt;path to layers&gt;
- &gt; mkdir wrll-linux-my_version
- &gt; cd wrll-linux-my_version
- &gt; echo "wrll-linux-2.6.27" &gt; include
- &gt; mkdir -p kernel-cache/ktypes/standard
- &gt; mkdir -p kernel-cache/bsp/common_pc
- &gt; echo "v2.6.29" &gt; kernel-cache/kver
- &gt; echo "branch common_pc-standard" &gt; kernel-cache/bsp/common_pc/common_pc.scc
- &gt; echo "kconf hardware common_pc.cfg" &gt;&gt; kernel-cache/bsp/common_pc/common_pc.scc
- &gt; echo "CONFIG_FOO=y" &gt; kernel-cache/bsp/common_pc/common_pc.cfg
- &gt; mkdir git
- &gt; cd git
- &gt; git clone &dash;&dash;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'>
- &dash;&dash;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'>
- &gt; cd build
- &gt; make linux_GIT_BASE=&lt;layer path&gt;/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>
-
-</article>
-<!--
-vim: expandtab tw=80 ts=4
--->