diff options
| author | Patrick Williams <patrick@stwcx.xyz> | 2016-08-17 14:31:25 -0500 |
|---|---|---|
| committer | Patrick Williams <patrick@stwcx.xyz> | 2016-08-22 16:43:26 +0000 |
| commit | 60f9d69e016b11c468c98ea75ba0a60c44afbbc4 (patch) | |
| tree | ecb49581a9e41a37943c22cd9ef3f63451b20ee7 /import-layers/yocto-poky/documentation/dev-manual/dev-manual-newbie.xml | |
| parent | e18c61205e0234b03697129c20cc69c9b3940efc (diff) | |
| download | talos-openbmc-60f9d69e016b11c468c98ea75ba0a60c44afbbc4.tar.gz talos-openbmc-60f9d69e016b11c468c98ea75ba0a60c44afbbc4.zip | |
yocto-poky: Move to import-layers subdir
We are going to import additional layers, so create a subdir to
hold all of the layers that we import with git-subtree.
Change-Id: I6f732153a22be8ca663035c518837e3cc5ec0799
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Diffstat (limited to 'import-layers/yocto-poky/documentation/dev-manual/dev-manual-newbie.xml')
| -rw-r--r-- | import-layers/yocto-poky/documentation/dev-manual/dev-manual-newbie.xml | 1710 |
1 files changed, 1710 insertions, 0 deletions
diff --git a/import-layers/yocto-poky/documentation/dev-manual/dev-manual-newbie.xml b/import-layers/yocto-poky/documentation/dev-manual/dev-manual-newbie.xml new file mode 100644 index 000000000..75c992f16 --- /dev/null +++ b/import-layers/yocto-poky/documentation/dev-manual/dev-manual-newbie.xml @@ -0,0 +1,1710 @@ +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" +"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" +[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > + +<chapter id='dev-manual-newbie'> + +<title>The Yocto Project Open Source Development Environment</title> + +<para> + This chapter helps you understand the Yocto Project as an open source development project. + In general, working in an open source environment is very different from working in a + closed, proprietary environment. + Additionally, the Yocto Project uses specific tools and constructs as part of its development + environment. + This chapter specifically addresses open source philosophy, using the + Yocto Project in a team environment, source repositories, Yocto Project + terms, licensing, the open source distributed version control system Git, + workflows, bug tracking, and how to submit changes. +</para> + +<section id='open-source-philosophy'> + <title>Open Source Philosophy</title> + + <para> + Open source philosophy is characterized by software development directed by peer production + and collaboration through an active community of developers. + Contrast this to the more standard centralized development models used by commercial software + companies where a finite set of developers produces a product for sale using a defined set + of procedures that ultimately result in an end product whose architecture and source material + are closed to the public. + </para> + + <para> + Open source projects conceptually have differing concurrent agendas, approaches, and production. + These facets of the development process can come from anyone in the public (community) that has a + stake in the software project. + The open source environment contains new copyright, licensing, domain, and consumer issues + that differ from the more traditional development environment. + In an open source environment, the end product, source material, and documentation are + all available to the public at no cost. + </para> + + <para> + A benchmark example of an open source project is the Linux kernel, which was initially conceived + and created by Finnish computer science student Linus Torvalds in 1991. + Conversely, a good example of a non-open source project is the + <trademark class='registered'>Windows</trademark> family of operating + systems developed by <trademark class='registered'>Microsoft</trademark> Corporation. + </para> + + <para> + Wikipedia has a good historical description of the Open Source Philosophy + <ulink url='http://en.wikipedia.org/wiki/Open_source'>here</ulink>. + You can also find helpful information on how to participate in the Linux Community + <ulink url='http://ldn.linuxfoundation.org/book/how-participate-linux-community'>here</ulink>. + </para> +</section> + +<section id="usingpoky-changes-collaborate"> + <title>Using the Yocto Project in a Team Environment</title> + + <para> + It might not be immediately clear how you can use the Yocto + Project in a team environment, or scale it for a large team of + developers. + One of the strengths of the Yocto Project is that it is extremely + flexible. + Thus, you can adapt it to many different use cases and scenarios. + However, these characteristics can cause a struggle if you are trying + to create a working setup that scales across a large team. + </para> + + <para> + To help with these types of situations, this section presents + some of the project's most successful experiences, + practices, solutions, and available technologies that work well. + Keep in mind, the information here is a starting point. + You can build off it and customize it to fit any + particular working environment and set of practices. + </para> + + <section id='best-practices-system-configurations'> + <title>System Configurations</title> + + <para> + Systems across a large team should meet the needs of + two types of developers: those working on the contents of the + operating system image itself and those developing applications. + Regardless of the type of developer, their workstations must + be both reasonably powerful and run Linux. + </para> + + <section id='best-practices-application-development'> + <title>Application Development</title> + + <para> + For developers who mainly do application level work + on top of an existing software stack, + the following list shows practices that work best. + For information on using a Software Development Kit (SDK), see + the + <ulink url='&YOCTO_DOCS_SDK_URL;#sdk-intro'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>: + <itemizedlist> + <listitem><para>Use a pre-built toolchain that + contains the software stack itself. + Then, develop the application code on top of the + stack. + This method works well for small numbers of relatively + isolated applications.</para></listitem> + <listitem><para>When possible, use the Yocto Project + plug-in for the <trademark class='trade'>Eclipse</trademark> IDE + and SDK development practices. + For more information, see the + "<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>". + </para></listitem> + <listitem><para>Keep your cross-development toolchains + updated. + You can do this through provisioning either as new + toolchain downloads or as updates through a package + update mechanism using <filename>opkg</filename> + to provide updates to an existing toolchain. + The exact mechanics of how and when to do this are a + question for local policy.</para></listitem> + <listitem><para>Use multiple toolchains installed locally + into different locations to allow development across + versions.</para></listitem> + </itemizedlist> + </para> + </section> + + <section id='best-practices-core-system-development'> + <title>Core System Development</title> + + <para> + For core system development, it is often best to have the + build system itself available on the developer workstations + so developers can run their own builds and directly + rebuild the software stack. + You should keep the core system unchanged as much as + possible and do your work in layers on top of the core system. + Doing so gives you a greater level of portability when + upgrading to new versions of the core system or Board + Support Packages (BSPs). + You can share layers amongst the developers of a particular + project and contain the policy configuration that defines + the project. + </para> + + <para> + Aside from the previous best practices, there exists a number + of tips and tricks that can help speed up core development + projects: + <itemizedlist> + <listitem><para>Use a + <ulink url='&YOCTO_DOCS_REF_URL;#shared-state-cache'>Shared State Cache</ulink> + (sstate) among groups of developers who are on a + fast network. + The best way to share sstate is through a + Network File System (NFS) share. + The first user to build a given component for the + first time contributes that object to the sstate, + while subsequent builds from other developers then + reuse the object rather than rebuild it themselves. + </para> + <para>Although it is possible to use other protocols for the + sstate such as HTTP and FTP, you should avoid these. + Using HTTP limits the sstate to read-only and + FTP provides poor performance. + </para></listitem> + <listitem><para>Have autobuilders contribute to the sstate + pool similarly to how the developer workstations + contribute. + For information, see the + "<link linkend='best-practices-autobuilders'>Autobuilders</link>" + section.</para></listitem> + <listitem><para>Build stand-alone tarballs that contain + "missing" system requirements if for some reason + developer workstations do not meet minimum system + requirements such as latest Python versions, + <filename>chrpath</filename>, or other tools. + You can install and relocate the tarball exactly as you + would the usual cross-development toolchain so that + all developers can meet minimum version requirements + on most distributions.</para></listitem> + <listitem><para>Use a small number of shared, + high performance systems for testing purposes + (e.g. dual, six-core Xeons with 24 Gbytes of RAM + and plenty of disk space). + Developers can use these systems for wider, more + extensive testing while they continue to develop + locally using their primary development system. + </para></listitem> + <listitem><para>Enable the PR Service when package feeds + need to be incremental with continually increasing + <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'>PR</ulink> + values. + Typically, this situation occurs when you use or + publish package feeds and use a shared state. + You should enable the PR Service for all users who + use the shared state pool. + For more information on the PR Service, see the + "<link linkend='working-with-a-pr-service'>Working With a PR Service</link>". + </para></listitem> + </itemizedlist> + </para> + </section> + </section> + + <section id='best-practices-source-control-management'> + <title>Source Control Management (SCM)</title> + + <para> + Keeping your + <ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink> + and any software you are developing under the + control of an SCM system that is compatible + with the OpenEmbedded build system is advisable. + Of the SCMs BitBake supports, the + Yocto Project team strongly recommends using + <link linkend='git'>Git</link>. + Git is a distributed system that is easy to backup, + allows you to work remotely, and then connects back to the + infrastructure. + <note> + For information about BitBake, see the + <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>. + </note> + </para> + + <para> + It is relatively easy to set up Git services and create + infrastructure like + <ulink url='&YOCTO_GIT_URL;'>http://git.yoctoproject.org</ulink>, + which is based on server software called + <filename>gitolite</filename> with <filename>cgit</filename> + being used to generate the web interface that lets you view the + repositories. + The <filename>gitolite</filename> software identifies users + using SSH keys and allows branch-based + access controls to repositories that you can control as little + or as much as necessary. + </para> + + <note> + The setup of these services is beyond the scope of this manual. + However, sites such as these exist that describe how to perform + setup: + <itemizedlist> + <listitem><para><ulink url='http://git-scm.com/book/ch4-8.html'>Git documentation</ulink>: + Describes how to install <filename>gitolite</filename> + on the server.</para></listitem> + <listitem><para><ulink url='http://sitaramc.github.com/gitolite/master-toc.html'>The <filename>gitolite</filename> master index</ulink>: + All topics for <filename>gitolite</filename>. + </para></listitem> + <listitem><para><ulink url='https://git.wiki.kernel.org/index.php/Interfaces,_frontends,_and_tools'>Interfaces, frontends, and tools</ulink>: + Documentation on how to create interfaces and frontends + for Git.</para></listitem> + </itemizedlist> + </note> + </section> + + <section id='best-practices-autobuilders'> + <title>Autobuilders</title> + + <para> + Autobuilders are often the core of a development project. + It is here that changes from individual developers are brought + together and centrally tested and subsequent decisions about + releases can be made. + Autobuilders also allow for "continuous integration" style + testing of software components and regression identification + and tracking. + </para> + + <para> + See "<ulink url='http://autobuilder.yoctoproject.org'>Yocto Project Autobuilder</ulink>" + for more information and links to buildbot. + The Yocto Project team has found this implementation + works well in this role. + A public example of this is the Yocto Project + Autobuilders, which we use to test the overall health of the + project. + </para> + + <para> + The features of this system are: + <itemizedlist> + <listitem><para>Highlights when commits break the build. + </para></listitem> + <listitem><para>Populates an sstate cache from which + developers can pull rather than requiring local + builds.</para></listitem> + <listitem><para>Allows commit hook triggers, + which trigger builds when commits are made. + </para></listitem> + <listitem><para>Allows triggering of automated image booting + and testing under the QuickEMUlator (QEMU). + </para></listitem> + <listitem><para>Supports incremental build testing and + from-scratch builds.</para></listitem> + <listitem><para>Shares output that allows developer + testing and historical regression investigation. + </para></listitem> + <listitem><para>Creates output that can be used for releases. + </para></listitem> + <listitem><para>Allows scheduling of builds so that resources + can be used efficiently.</para></listitem> + </itemizedlist> + </para> + </section> + + <section id='best-practices-policies-and-change-flow'> + <title>Policies and Change Flow</title> + + <para> + The Yocto Project itself uses a hierarchical structure and a + pull model. + Scripts exist to create and send pull requests + (i.e. <filename>create-pull-request</filename> and + <filename>send-pull-request</filename>). + This model is in line with other open source projects where + maintainers are responsible for specific areas of the project + and a single maintainer handles the final "top-of-tree" merges. + </para> + + <note> + You can also use a more collective push model. + The <filename>gitolite</filename> software supports both the + push and pull models quite easily. + </note> + + <para> + As with any development environment, it is important + to document the policy used as well as any main project + guidelines so they are understood by everyone. + It is also a good idea to have well structured + commit messages, which are usually a part of a project's + guidelines. + Good commit messages are essential when looking back in time and + trying to understand why changes were made. + </para> + + <para> + If you discover that changes are needed to the core layer of the + project, it is worth sharing those with the community as soon + as possible. + Chances are if you have discovered the need for changes, someone + else in the community needs them also. + </para> + </section> + + <section id='best-practices-summary'> + <title>Summary</title> + + <para> + This section summarizes the key recommendations described in the + previous sections: + <itemizedlist> + <listitem><para>Use <link linkend='git'>Git</link> + as the source control system.</para></listitem> + <listitem><para>Maintain your Metadata in layers that make sense + for your situation. + See the "<link linkend='understanding-and-creating-layers'>Understanding + and Creating Layers</link>" section for more information on + layers.</para></listitem> + <listitem><para> + Separate the project's Metadata and code by using + separate Git repositories. + See the + "<link linkend='yocto-project-repositories'>Yocto Project Source Repositories</link>" + section for information on these repositories. + See the + "<link linkend='getting-setup'>Getting Set Up</link>" + section for information on how to set up local Git + repositories for related upstream Yocto Project + Git repositories. + </para></listitem> + <listitem><para>Set up the directory for the shared state cache + (<ulink url='&YOCTO_DOCS_REF_URL;#var-SSTATE_DIR'><filename>SSTATE_DIR</filename></ulink>) + where it makes sense. + For example, set up the sstate cache on a system used + by developers in the same organization and share the + same source directories on their machines. + </para></listitem> + <listitem><para>Set up an Autobuilder and have it populate the + sstate cache and source directories.</para></listitem> + <listitem><para>The Yocto Project community encourages you + to send patches to the project to fix bugs or add features. + If you do submit patches, follow the project commit + guidelines for writing good commit messages. + See the "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + section.</para></listitem> + <listitem><para>Send changes to the core sooner than later + as others are likely to run into the same issues. + For some guidance on mailing lists to use, see the list in the + "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + section. + For a description of the available mailing lists, see the + "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing Lists</ulink>" + section in the Yocto Project Reference Manual. + </para></listitem> + </itemizedlist> + </para> + </section> +</section> + +<section id='yocto-project-repositories'> + <title>Yocto Project Source Repositories</title> + + <para> + The Yocto Project team maintains complete source repositories for all + Yocto Project files at + <ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi'></ulink>. + This web-based source code browser is organized into categories by + function such as IDE Plugins, Matchbox, Poky, Yocto Linux Kernel, and + so forth. + From the interface, you can click on any particular item in the "Name" + column and see the URL at the bottom of the page that you need to clone + a Git repository for that particular item. + Having a local Git repository of the + <link linkend='source-directory'>Source Directory</link>, which is + usually named "poky", allows + you to make changes, contribute to the history, and ultimately enhance + the Yocto Project's tools, Board Support Packages, and so forth. + </para> + + <para> + For any supported release of Yocto Project, you can also go to the + <ulink url='&YOCTO_HOME_URL;'>Yocto Project Website</ulink> and + select the "Downloads" tab and get a released tarball of the + <filename>poky</filename> repository or any supported BSP tarballs. + Unpacking these tarballs gives you a snapshot of the released + files. + <note><title>Notes</title> + <itemizedlist> + <listitem><para> + The recommended method for setting up the Yocto Project + <link linkend='source-directory'>Source Directory</link> + and the files for supported BSPs + (e.g., <filename>meta-intel</filename>) is to use + <link linkend='git'>Git</link> to create a local copy of + the upstream repositories. + </para></listitem> + <listitem><para> + Be sure to always work in matching branches for both + the selected BSP repository and the + <link linkend='source-directory'>Source Directory</link> + (i.e. <filename>poky</filename>) repository. + For example, if you have checked out the "master" branch + of <filename>poky</filename> and you are going to use + <filename>meta-intel</filename>, be sure to checkout the + "master" branch of <filename>meta-intel</filename>. + </para></listitem> + </itemizedlist> + </note> + </para> + + <para> + In summary, here is where you can get the project files needed for development: + <itemizedlist> + <listitem><para id='source-repositories'><emphasis><ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi'>Source Repositories:</ulink></emphasis> + This area contains IDE Plugins, Matchbox, Poky, Poky Support, Tools, Yocto Linux Kernel, and Yocto + Metadata Layers. + You can create local copies of Git repositories for each of these areas.</para> + <para> + <imagedata fileref="figures/source-repos.png" align="center" width="6in" depth="4in" /> + </para></listitem> + <listitem><para><anchor id='index-downloads' /><emphasis><ulink url='&YOCTO_DL_URL;/releases/'>Index of /releases:</ulink></emphasis> + This is an index of releases such as + the <trademark class='trade'>Eclipse</trademark> + Yocto Plug-in, miscellaneous support, Poky, Pseudo, installers for cross-development toolchains, + and all released versions of Yocto Project in the form of images or tarballs. + Downloading and extracting these files does not produce a local copy of the + Git repository but rather a snapshot of a particular release or image.</para> + <para> + <imagedata fileref="figures/index-downloads.png" align="center" width="6in" depth="3.5in" /> + </para></listitem> + <listitem><para><emphasis>"Downloads" page for the + <ulink url='&YOCTO_HOME_URL;'>Yocto Project Website</ulink>:</emphasis> + Access this page by going to the website and then selecting + the "Downloads" tab. + This page allows you to download any Yocto Project + release or Board Support Package (BSP) in tarball form. + The tarballs are similar to those found in the + <ulink url='&YOCTO_DL_URL;/releases/'>Index of /releases:</ulink> area.</para> + <para> + <imagedata fileref="figures/yp-download.png" align="center" width="6in" depth="4in" /> + </para></listitem> + </itemizedlist> + </para> +</section> + +<section id='yocto-project-terms'> + <title>Yocto Project Terms</title> + + <para> + Following is a list of terms and definitions users new to the Yocto Project development + environment might find helpful. + While some of these terms are universal, the list includes them just in case: + <itemizedlist> + <listitem><para><emphasis>Append Files:</emphasis> Files that append build information to + a recipe file. + Append files are known as BitBake append files and <filename>.bbappend</filename> files. + The OpenEmbedded build system expects every append file to have a corresponding + recipe (<filename>.bb</filename>) file. + Furthermore, the append file and corresponding recipe file + must use the same root filename. + The filenames can differ only in the file type suffix used (e.g. + <filename>formfactor_0.0.bb</filename> and <filename>formfactor_0.0.bbappend</filename>). + </para> + <para>Information in append files extends or overrides the + information in the similarly-named recipe file. + For an example of an append file in use, see the + "<link linkend='using-bbappend-files'>Using .bbappend Files</link>" section. + <note> + Append files can also use wildcard patterns in their version numbers + so they can be applied to more than one version of the underlying recipe file. + </note> + </para></listitem> + <listitem><para id='bitbake-term'><emphasis>BitBake:</emphasis> + The task executor and scheduler used by the OpenEmbedded build + system to build images. + For more information on BitBake, see the + <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>. + </para></listitem> + <listitem> + <para id='build-directory'><emphasis>Build Directory:</emphasis> + This term refers to the area used by the OpenEmbedded build + system for builds. + The area is created when you <filename>source</filename> the + setup environment script that is found in the Source Directory + (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink> + or + <ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>). + The <ulink url='&YOCTO_DOCS_REF_URL;#var-TOPDIR'><filename>TOPDIR</filename></ulink> + variable points to the Build Directory.</para> + + <para> + You have a lot of flexibility when creating the Build + Directory. + Following are some examples that show how to create the + directory. + The examples assume your + <link linkend='source-directory'>Source Directory</link> is + named <filename>poky</filename>: + <itemizedlist> + <listitem><para>Create the Build Directory inside your + Source Directory and let the name of the Build + Directory default to <filename>build</filename>: + <literallayout class='monospaced'> + $ cd $HOME/poky + $ source &OE_INIT_FILE; + </literallayout></para></listitem> + <listitem><para>Create the Build Directory inside your + home directory and specifically name it + <filename>test-builds</filename>: + <literallayout class='monospaced'> + $ cd $HOME + $ source poky/&OE_INIT_FILE; test-builds + </literallayout></para></listitem> + <listitem><para> + Provide a directory path and + specifically name the Build Directory. + Any intermediate folders in the pathname must + exist. + This next example creates a Build Directory named + <filename>YP-&POKYVERSION;</filename> + in your home directory within the existing + directory <filename>mybuilds</filename>: + <literallayout class='monospaced'> + $cd $HOME + $ source $HOME/poky/&OE_INIT_FILE; $HOME/mybuilds/YP-&POKYVERSION; + </literallayout></para></listitem> + </itemizedlist> + <note> + By default, the Build Directory contains + <ulink url='&YOCTO_DOCS_REF_URL;#var-TMPDIR'><filename>TMPDIR</filename></ulink>, + which is a temporary directory the build system uses for + its work. + <filename>TMPDIR</filename> cannot be under NFS. + Thus, by default, the Build Directory cannot be under NFS. + However, if you need the Build Directory to be under NFS, + you can set this up by setting <filename>TMPDIR</filename> + in your <filename>local.conf</filename> file + to use a local drive. + Doing so effectively separates <filename>TMPDIR</filename> + from <filename>TOPDIR</filename>, which is the Build + Directory. + </note> + </para></listitem> + <listitem><para><emphasis>Classes:</emphasis> Files that provide for logic encapsulation + and inheritance so that commonly used patterns can be defined once and then easily used + in multiple recipes. + For reference information on the Yocto Project classes, see the + "<ulink url='&YOCTO_DOCS_REF_URL;#ref-classes'>Classes</ulink>" chapter of the + Yocto Project Reference Manual. + Class files end with the <filename>.bbclass</filename> filename extension. + </para></listitem> + <listitem><para><emphasis>Configuration File:</emphasis> + Configuration information in various <filename>.conf</filename> + files provides global definitions of variables. + The <filename>conf/local.conf</filename> configuration file in + the + <link linkend='build-directory'>Build Directory</link> + contains user-defined variables that affect every build. + The <filename>meta-poky/conf/distro/poky.conf</filename> + configuration file defines Yocto "distro" configuration + variables used only when building with this policy. + Machine configuration files, which + are located throughout the + <link linkend='source-directory'>Source Directory</link>, define + variables for specific hardware and are only used when building + for that target (e.g. the + <filename>machine/beaglebone.conf</filename> configuration + file defines variables for the Texas Instruments ARM Cortex-A8 + development board). + Configuration files end with a <filename>.conf</filename> + filename extension. + </para></listitem> + <listitem><para id='cross-development-toolchain'> + <emphasis>Cross-Development Toolchain:</emphasis> + In general, a cross-development toolchain is a collection of + software development tools and utilities that run on one + architecture and allow you to develop software for a + different, or targeted, architecture. + These toolchains contain cross-compilers, linkers, and + debuggers that are specific to the target architecture. + </para> + + <para>The Yocto Project supports two different cross-development + toolchains: + <itemizedlist> + <listitem><para>A toolchain only used by and within + BitBake when building an image for a target + architecture.</para></listitem> + <listitem><para>A relocatable toolchain used outside of + BitBake by developers when developing applications + that will run on a targeted device. + </para></listitem> + </itemizedlist> + </para> + + <para> + Creation of these toolchains is simple and automated. + For information on toolchain concepts as they apply to the + Yocto Project, see the + "<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>" + section in the Yocto Project Reference Manual. + You can also find more information on using the + relocatable toolchain in the + <ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>. + </para></listitem> + <listitem><para><emphasis>Image:</emphasis> + An image is an artifact of the BitBake build process given + a collection of recipes and related Metadata. + Images are the binary output that run on specific hardware or + QEMU and are used for specific use-cases. + For a list of the supported image types that the Yocto Project provides, see the + "<ulink url='&YOCTO_DOCS_REF_URL;#ref-images'>Images</ulink>" + chapter in the Yocto Project Reference Manual.</para></listitem> + <listitem><para id='layer'><emphasis>Layer:</emphasis> A collection of recipes representing the core, + a BSP, or an application stack. + For a discussion specifically on BSP Layers, see the + "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>" + section in the Yocto Project Board Support Packages (BSP) + Developer's Guide.</para></listitem> + <listitem><para id='metadata'><emphasis>Metadata:</emphasis> + The files that BitBake parses when building an image. + In general, Metadata includes recipes, classes, and + configuration files. + In the context of the kernel ("kernel Metadata"), + it refers to Metadata in the <filename>meta</filename> + branches of the kernel source Git repositories. + </para></listitem> + <listitem><para id='oe-core'><emphasis>OE-Core:</emphasis> A core set of Metadata originating + with OpenEmbedded (OE) that is shared between OE and the Yocto Project. + This Metadata is found in the <filename>meta</filename> directory of the + <link linkend='source-directory'>Source Directory</link>.</para></listitem> + <listitem><para id='build-system-term'><emphasis>OpenEmbedded Build System:</emphasis> + The build system specific to the Yocto Project. + The OpenEmbedded build system is based on another project known + as "Poky", which uses + <link linkend='bitbake-term'>BitBake</link> as the task + executor. + Throughout the Yocto Project documentation set, the + OpenEmbedded build system is sometimes referred to simply + as "the build system". + If other build systems, such as a host or target build system + are referenced, the documentation clearly states the + difference. + <note> + For some historical information about Poky, see the + <link linkend='poky'>Poky</link> term. + </note> + </para></listitem> + <listitem><para><emphasis>Package:</emphasis> + In the context of the Yocto Project, this term refers to a + recipe's packaged output produced by BitBake (i.e. a + "baked recipe"). + A package is generally the compiled binaries produced from the + recipe's sources. + You "bake" something by running it through BitBake.</para> + <para>It is worth noting that the term "package" can, in general, have subtle + meanings. For example, the packages referred to in the + "<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>" section are + compiled binaries that, when installed, add functionality to your Linux + distribution.</para> + <para>Another point worth noting is that historically within the Yocto Project, + recipes were referred to as packages - thus, the existence of several BitBake + variables that are seemingly mis-named, + (e.g. <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>, + <ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>, and + <ulink url='&YOCTO_DOCS_REF_URL;#var-PE'><filename>PE</filename></ulink>). + </para></listitem> + <listitem><para><emphasis>Package Groups:</emphasis> + Arbitrary groups of software Recipes. + You use package groups to hold recipes that, when built, + usually accomplish a single task. + For example, a package group could contain the recipes for a + company’s proprietary or value-add software. + Or, the package group could contain the recipes that enable + graphics. + A package group is really just another recipe. + Because package group files are recipes, they end with the + <filename>.bb</filename> filename extension.</para></listitem> + <listitem><para id='poky'><emphasis>Poky:</emphasis> + The term "poky" can mean several things. + In its most general sense, it is an open-source + project that was initially developed by OpenedHand. + With OpenedHand, poky was developed off of the existing + OpenEmbedded build system becoming a commercially + supportable build system for embedded Linux. + After Intel Corporation acquired OpenedHand, the + project poky became the basis for the Yocto Project's + build system.</para> + <para>Within the Yocto Project source repositories, + <filename>poky</filename> exists as a separate Git + repository you can clone to yield a local copy on your + host system. + Thus, "poky" can refer to the local copy of the Source + Directory used for development within the Yocto + Project.</para> + <para>Finally, "poky" can refer to the default + <ulink url='&YOCTO_DOCS_REF_URL;#var-DISTRO'><filename>DISTRO</filename></ulink> + (i.e. distribution) created when you use the Yocto + Project in conjunction with the + <filename>poky</filename> repository to build an image. + </para></listitem> + <listitem><para><emphasis>Recipe:</emphasis> + A set of instructions for building packages. + A recipe describes where you get source code, which patches + to apply, how to configure the source, how to compile it and so on. + Recipes also describe dependencies for libraries or for other + recipes. + Recipes represent the logical unit of execution, the software + to build, the images to build, and use the + <filename>.bb</filename> file extension. + </para></listitem> + <listitem> + <para id='source-directory'><emphasis>Source Directory:</emphasis> + This term refers to the directory structure created as a result + of creating a local copy of the <filename>poky</filename> Git + repository <filename>git://git.yoctoproject.org/poky</filename> + or expanding a released <filename>poky</filename> tarball. + <note> + Creating a local copy of the <filename>poky</filename> + Git repository is the recommended method for setting up + your Source Directory. + </note> + Sometimes you might hear the term "poky directory" used to refer + to this directory structure. + <note> + The OpenEmbedded build system does not support file or + directory names that contain spaces. + Be sure that the Source Directory you use does not contain + these types of names. + </note></para> + + <para>The Source Directory contains BitBake, Documentation, + Metadata and other files that all support the Yocto Project. + Consequently, you must have the Source Directory in place on + your development system in order to do any development using + the Yocto Project.</para> + + <para>When you create a local copy of the Git repository, you + can name the repository anything you like. + Throughout much of the documentation, "poky" + is used as the name of the top-level folder of the local copy of + the poky Git repository. + So, for example, cloning the <filename>poky</filename> Git + repository results in a local Git repository whose top-level + folder is also named "poky".</para> + + <para>While it is not recommended that you use tarball expansion + to set up the Source Directory, if you do, the top-level + directory name of the Source Directory is derived from the + Yocto Project release tarball. + For example, downloading and unpacking + <filename>&YOCTO_POKY_TARBALL;</filename> results in a + Source Directory whose root folder is named + <filename>&YOCTO_POKY;</filename>.</para> + + <para>It is important to understand the differences between the + Source Directory created by unpacking a released tarball as + compared to cloning + <filename>git://git.yoctoproject.org/poky</filename>. + When you unpack a tarball, you have an exact copy of the files + based on the time of release - a fixed release point. + Any changes you make to your local files in the Source Directory + are on top of the release and will remain local only. + On the other hand, when you clone the <filename>poky</filename> + Git repository, you have an active development repository with + access to the upstream repository's branches and tags. + In this case, any local changes you make to the local + Source Directory can be later applied to active development + branches of the upstream <filename>poky</filename> Git + repository.</para> + + <para>For more information on concepts related to Git + repositories, branches, and tags, see the + "<link linkend='repositories-tags-and-branches'>Repositories, Tags, and Branches</link>" + section.</para></listitem> + <listitem><para><emphasis>Task:</emphasis> + A unit of execution for BitBake (e.g. + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-compile'><filename>do_compile</filename></ulink>, + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>do_fetch</filename></ulink>, + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-patch'><filename>do_patch</filename></ulink>, + and so forth). + </para></listitem> + <listitem><para><emphasis>Upstream:</emphasis> A reference to source code or repositories + that are not local to the development system but located in a master area that is controlled + by the maintainer of the source code. + For example, in order for a developer to work on a particular piece of code, they need to + first get a copy of it from an "upstream" source.</para></listitem> + </itemizedlist> + </para> +</section> + +<section id='licensing'> + <title>Licensing</title> + + <para> + Because open source projects are open to the public, they have different licensing structures in place. + License evolution for both Open Source and Free Software has an interesting history. + If you are interested in this history, you can find basic information here: + <itemizedlist> + <listitem><para><ulink url='http://en.wikipedia.org/wiki/Open-source_license'>Open source license history</ulink> + </para></listitem> + <listitem><para><ulink url='http://en.wikipedia.org/wiki/Free_software_license'>Free software license + history</ulink></para></listitem> + </itemizedlist> + </para> + + <para> + In general, the Yocto Project is broadly licensed under the Massachusetts Institute of Technology + (MIT) License. + MIT licensing permits the reuse of software within proprietary software as long as the + license is distributed with that software. + MIT is also compatible with the GNU General Public License (GPL). + Patches to the Yocto Project follow the upstream licensing scheme. + You can find information on the MIT license + <ulink url='http://www.opensource.org/licenses/mit-license.php'>here</ulink>. + You can find information on the GNU GPL <ulink url='http://www.opensource.org/licenses/LGPL-3.0'> + here</ulink>. + </para> + + <para> + When you build an image using the Yocto Project, the build process uses a + known list of licenses to ensure compliance. + You can find this list in the + <link linkend='source-directory'>Source Directory</link> at + <filename>meta/files/common-licenses</filename>. + Once the build completes, the list of all licenses found and used during that build are + kept in the + <link linkend='build-directory'>Build Directory</link> at + <filename>tmp/deploy/licenses</filename>. + </para> + + <para> + If a module requires a license that is not in the base list, the build process + generates a warning during the build. + These tools make it easier for a developer to be certain of the licenses with which + their shipped products must comply. + However, even with these tools it is still up to the developer to resolve potential licensing issues. + </para> + + <para> + The base list of licenses used by the build process is a combination of the Software Package + Data Exchange (SPDX) list and the Open Source Initiative (OSI) projects. + <ulink url='http://spdx.org'>SPDX Group</ulink> is a working group of the Linux Foundation + that maintains a specification + for a standard format for communicating the components, licenses, and copyrights + associated with a software package. + <ulink url='http://opensource.org'>OSI</ulink> is a corporation dedicated to the Open Source + Definition and the effort for reviewing and approving licenses that + conform to the Open Source Definition (OSD). + </para> + + <para> + You can find a list of the combined SPDX and OSI licenses that the + Yocto Project uses in the + <filename>meta/files/common-licenses</filename> directory in your + <link linkend='source-directory'>Source Directory</link>. + </para> + + <para> + For information that can help you maintain compliance with various + open source licensing during the lifecycle of a product created using + the Yocto Project, see the + "<link linkend='maintaining-open-source-license-compliance-during-your-products-lifecycle'>Maintaining Open Source License Compliance During Your Product's Lifecycle</link>" + section. + </para> +</section> + +<section id='git'> + <title>Git</title> + + <para> + The Yocto Project makes extensive use of Git, + which is a free, open source distributed version control system. + Git supports distributed development, non-linear development, and can handle large projects. + It is best that you have some fundamental understanding of how Git tracks projects and + how to work with Git if you are going to use the Yocto Project for development. + This section provides a quick overview of how Git works and provides you with a summary + of some essential Git commands. + </para> + + <para> + For more information on Git, see + <ulink url='http://git-scm.com/documentation'></ulink>. + If you need to download Git, go to <ulink url='http://git-scm.com/download'></ulink>. + </para> + + <section id='repositories-tags-and-branches'> + <title>Repositories, Tags, and Branches</title> + + <para> + As mentioned earlier in the section + "<link linkend='yocto-project-repositories'>Yocto Project Source Repositories</link>", + the Yocto Project maintains source repositories at + <ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink>. + If you look at this web-interface of the repositories, each item is a separate + Git repository. + </para> + + <para> + Git repositories use branching techniques that track content change (not files) + within a project (e.g. a new feature or updated documentation). + Creating a tree-like structure based on project divergence allows for excellent historical + information over the life of a project. + This methodology also allows for an environment from which you can do lots of + local experimentation on projects as you develop changes or new features. + </para> + + <para> + A Git repository represents all development efforts for a given project. + For example, the Git repository <filename>poky</filename> contains all changes + and developments for Poky over the course of its entire life. + That means that all changes that make up all releases are captured. + The repository maintains a complete history of changes. + </para> + + <para> + You can create a local copy of any repository by "cloning" it with the Git + <filename>clone</filename> command. + When you clone a Git repository, you end up with an identical copy of the + repository on your development system. + Once you have a local copy of a repository, you can take steps to develop locally. + For examples on how to clone Git repositories, see the + "<link linkend='getting-setup'>Getting Set Up</link>" section. + </para> + + <para> + It is important to understand that Git tracks content change and + not files. + Git uses "branches" to organize different development efforts. + For example, the <filename>poky</filename> repository has + several branches that include the current + <filename>&DISTRO_NAME_NO_CAP;</filename> branch, the + <filename>master</filename> branch, and many branches for past + Yocto Project releases. + You can see all the branches by going to + <ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/'></ulink> and + clicking on the + <filename><ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/refs/heads'>[...]</ulink></filename> + link beneath the "Branch" heading. + </para> + + <para> + Each of these branches represents a specific area of development. + The <filename>master</filename> branch represents the current or most recent + development. + All other branches represent offshoots of the <filename>master</filename> + branch. + </para> + + <para> + When you create a local copy of a Git repository, the copy has the same set + of branches as the original. + This means you can use Git to create a local working area (also called a branch) + that tracks a specific development branch from the source Git repository. + in other words, you can define your local Git environment to work on any development + branch in the repository. + To help illustrate, here is a set of commands that creates a local copy of the + <filename>poky</filename> Git repository and then creates and checks out a local + Git branch that tracks the Yocto Project &DISTRO; Release (&DISTRO_NAME;) development: + <literallayout class='monospaced'> + $ cd ~ + $ git clone git://git.yoctoproject.org/poky + $ cd poky + $ git checkout -b &DISTRO_NAME_NO_CAP; origin/&DISTRO_NAME_NO_CAP; + </literallayout> + In this example, the name of the top-level directory of your local + <link linkend='source-directory'>Source Directory</link> + is "poky" and the name of that local working area (local branch) + you just created and checked out is "&DISTRO_NAME_NO_CAP;". + The files in your local repository now reflect the same files that + are in the "&DISTRO_NAME_NO_CAP;" development branch of the + Yocto Project's "poky" upstream repository. + It is important to understand that when you create and checkout a + local working branch based on a branch name, + your local environment matches the "tip" of that development branch + at the time you created your local branch, which could be + different from the files at the time of a similarly named release. + In other words, creating and checking out a local branch based on + the "&DISTRO_NAME_NO_CAP;" branch name is not the same as + cloning and checking out the "master" branch. + Keep reading to see how you create a local snapshot of a Yocto + Project Release. + </para> + + <para> + Git uses "tags" to mark specific changes in a repository. + Typically, a tag is used to mark a special point such as the final + change before a project is released. + You can see the tags used with the <filename>poky</filename> Git + repository by going to + <ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/'></ulink> and + clicking on the + <filename><ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/refs/tags'>[...]</ulink></filename> + link beneath the "Tag" heading. + </para> + + <para> + Some key tags are + <filename>dizzy-12.0.0</filename>, + <filename>fido-13.0.0</filename>, + <filename>jethro-14.0.0</filename>, and + <filename>&DISTRO_NAME_NO_CAP;-&POKYVERSION;</filename>. + These tags represent Yocto Project releases. + </para> + + <para> + When you create a local copy of the Git repository, you also have access to all the + tags. + Similar to branches, you can create and checkout a local working Git branch based + on a tag name. + When you do this, you get a snapshot of the Git repository that reflects + the state of the files when the change was made associated with that tag. + The most common use is to checkout a working branch that matches a specific + Yocto Project release. + Here is an example: + <literallayout class='monospaced'> + $ cd ~ + $ git clone git://git.yoctoproject.org/poky + $ cd poky + $ git checkout -b my-&DISTRO_NAME_NO_CAP;-&POKYVERSION; &DISTRO_NAME_NO_CAP;-&POKYVERSION; + </literallayout> + In this example, the name of the top-level directory of your local Yocto Project + Files Git repository is <filename>poky</filename>. + And, the name of the local branch you have created and checked out is + <filename>my-&DISTRO_NAME_NO_CAP;-&POKYVERSION;</filename>. + The files in your repository now exactly match the Yocto Project &DISTRO; + Release tag (<filename>&DISTRO_NAME_NO_CAP;-&POKYVERSION;</filename>). + It is important to understand that when you create and checkout a local + working branch based on a tag, your environment matches a specific point + in time and not the entire development branch. + </para> + </section> + + <section id='basic-commands'> + <title>Basic Commands</title> + + <para> + Git has an extensive set of commands that lets you manage changes and perform + collaboration over the life of a project. + Conveniently though, you can manage with a small set of basic operations and workflows + once you understand the basic philosophy behind Git. + You do not have to be an expert in Git to be functional. + A good place to look for instruction on a minimal set of Git commands is + <ulink url='http://git-scm.com/documentation'>here</ulink>. + If you need to download Git, you can do so + <ulink url='http://git-scm.com/download'>here</ulink>, although + any reasonably current Linux distribution should already have an + installable package for Git. + </para> + + <para> + If you do not know much about Git, you should educate + yourself by visiting the links previously mentioned. + </para> + + <para> + The following list briefly describes some basic Git operations as a way to get started. + As with any set of commands, this list (in most cases) simply shows the base command and + omits the many arguments they support. + See the Git documentation for complete descriptions and strategies on how to use these commands: + <itemizedlist> + <listitem><para><emphasis><filename>git init</filename>:</emphasis> Initializes an empty Git repository. + You cannot use Git commands unless you have a <filename>.git</filename> repository.</para></listitem> + <listitem><para><emphasis><filename>git clone</filename>:</emphasis> + Creates a local clone of a Git repository. + During collaboration, this command allows you to create a + local Git repository that is on equal footing with a fellow + developer’s Git repository. + </para></listitem> + <listitem><para><emphasis><filename>git add</filename>:</emphasis> Stages updated file contents + to the index that + Git uses to track changes. + You must stage all files that have changed before you can commit them.</para></listitem> + <listitem><para><emphasis><filename>git commit</filename>:</emphasis> Creates a "commit" that documents + the changes you made. + Commits are used for historical purposes, for determining if a maintainer of a project + will allow the change, and for ultimately pushing the change from your local Git repository + into the project’s upstream (or master) repository.</para></listitem> + <listitem><para><emphasis><filename>git status</filename>:</emphasis> Reports any modified files that + possibly need to be staged and committed.</para></listitem> + <listitem><para><emphasis><filename>git checkout</filename> <replaceable>branch-name</replaceable>:</emphasis> Changes + your working branch. + This command is analogous to "cd".</para></listitem> + <listitem><para><emphasis><filename>git checkout –b</filename> <replaceable>working-branch</replaceable>:</emphasis> Creates + a working branch on your local machine where you can isolate work. + It is a good idea to use local branches when adding specific features or changes. + This way if you do not like what you have done you can easily get rid of the work.</para></listitem> + <listitem><para><emphasis><filename>git branch</filename>:</emphasis> Reports + existing local branches and + tells you the branch in which you are currently working.</para></listitem> + <listitem><para><emphasis><filename>git branch -D</filename> <replaceable>branch-name</replaceable>:</emphasis> + Deletes an existing local branch. + You need to be in a local branch other than the one you are deleting + in order to delete <replaceable>branch-name</replaceable>.</para></listitem> + <listitem><para><emphasis><filename>git pull</filename>:</emphasis> Retrieves information + from an upstream Git + repository and places it in your local Git repository. + You use this command to make sure you are synchronized with the repository + from which you are basing changes (.e.g. the master branch).</para></listitem> + <listitem><para><emphasis><filename>git push</filename>:</emphasis> + Sends all your committed local changes to an upstream Git + repository (e.g. a contribution repository). + The maintainer of the project draws from these repositories + when adding changes to the project’s master repository or + other development branch. + </para></listitem> + <listitem><para><emphasis><filename>git merge</filename>:</emphasis> Combines or adds changes from one + local branch of your repository with another branch. + When you create a local Git repository, the default branch is named "master". + A typical workflow is to create a temporary branch for isolated work, make and commit your + changes, switch to your local master branch, merge the changes from the temporary branch into the + local master branch, and then delete the temporary branch.</para></listitem> + <listitem><para><emphasis><filename>git cherry-pick</filename>:</emphasis> Choose and apply specific + commits from one branch into another branch. + There are times when you might not be able to merge all the changes in one branch with + another but need to pick out certain ones.</para></listitem> + <listitem><para><emphasis><filename>gitk</filename>:</emphasis> Provides a GUI view of the branches + and changes in your local Git repository. + This command is a good way to graphically see where things have diverged in your + local repository.</para></listitem> + <listitem><para><emphasis><filename>git log</filename>:</emphasis> Reports a history of your changes to the + repository.</para></listitem> + <listitem><para><emphasis><filename>git diff</filename>:</emphasis> Displays line-by-line differences + between your local working files and the same files in the upstream Git repository that your + branch currently tracks.</para></listitem> + </itemizedlist> + </para> + </section> +</section> + +<section id='workflows'> + <title>Workflows</title> + + <para> + This section provides some overview on workflows using Git. + In particular, the information covers basic practices that describe roles and actions in a + collaborative development environment. + Again, if you are familiar with this type of development environment, you might want to just + skip this section. + </para> + + <para> + The Yocto Project files are maintained using Git in a "master" branch whose Git history + tracks every change and whose structure provides branches for all diverging functionality. + Although there is no need to use Git, many open source projects do so. + For the Yocto Project, a key individual called the "maintainer" is responsible for the "master" + branch of a given Git repository. + The "master" branch is the “upstream” repository where the final builds of the project occur. + The maintainer is responsible for accepting changes from other developers and for + organizing the underlying branch structure to reflect release strategies and so forth. + <note>For information on finding out who is responsible for (maintains) + a particular area of code, see the + "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + section. + </note> + </para> + + <para> + The project also has an upstream contribution Git repository named + <filename>poky-contrib</filename>. + You can see all the branches in this repository using the web interface + of the + <ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink> organized + within the "Poky Support" area. + These branches temporarily hold changes to the project that have been + submitted or committed by the Yocto Project development team and by + community members who contribute to the project. + The maintainer determines if the changes are qualified to be moved + from the "contrib" branches into the "master" branch of the Git + repository. + </para> + + <para> + Developers (including contributing community members) create and maintain cloned repositories + of the upstream "master" branch. + These repositories are local to their development platforms and are used to develop changes. + When a developer is satisfied with a particular feature or change, they "push" the changes + to the appropriate "contrib" repository. + </para> + + <para> + Developers are responsible for keeping their local repository up-to-date with "master". + They are also responsible for straightening out any conflicts that might arise within files + that are being worked on simultaneously by more than one person. + All this work is done locally on the developer’s machines before anything is pushed to a + "contrib" area and examined at the maintainer’s level. + </para> + + <para> + A somewhat formal method exists by which developers commit changes and push them into the + "contrib" area and subsequently request that the maintainer include them into "master" + This process is called “submitting a patch” or "submitting a change." + For information on submitting patches and changes, see the + "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" section. + </para> + + <para> + To summarize the environment: a single point of entry exists for + changes into the project’s "master" branch of the Git repository, + which is controlled by the project’s maintainer. + And, a set of developers exist who independently develop, test, and + submit changes to "contrib" areas for the maintainer to examine. + The maintainer then chooses which changes are going to become a + permanent part of the project. + </para> + + <para> + <imagedata fileref="figures/git-workflow.png" width="6in" depth="3in" align="left" scalefit="1" /> + </para> + + <para> + While each development environment is unique, there are some best practices or methods + that help development run smoothly. + The following list describes some of these practices. + For more information about Git workflows, see the workflow topics in the + <ulink url='http://book.git-scm.com'>Git Community Book</ulink>. + <itemizedlist> + <listitem><para><emphasis>Make Small Changes:</emphasis> It is best to keep the changes you commit + small as compared to bundling many disparate changes into a single commit. + This practice not only keeps things manageable but also allows the maintainer + to more easily include or refuse changes.</para> + <para>It is also good practice to leave the repository in a state that allows you to + still successfully build your project. In other words, do not commit half of a feature, + then add the other half as a separate, later commit. + Each commit should take you from one buildable project state to another + buildable state.</para></listitem> + <listitem><para><emphasis>Use Branches Liberally:</emphasis> It is very easy to create, use, and + delete local branches in your working Git repository. + You can name these branches anything you like. + It is helpful to give them names associated with the particular feature or change + on which you are working. + Once you are done with a feature or change and have merged it + into your local master branch, simply discard the temporary + branch.</para></listitem> + <listitem><para><emphasis>Merge Changes:</emphasis> The <filename>git merge</filename> + command allows you to take the + changes from one branch and fold them into another branch. + This process is especially helpful when more than a single developer might be working + on different parts of the same feature. + Merging changes also automatically identifies any collisions or "conflicts" + that might happen as a result of the same lines of code being altered by two different + developers.</para></listitem> + <listitem><para><emphasis>Manage Branches:</emphasis> Because branches are easy to use, you should + use a system where branches indicate varying levels of code readiness. + For example, you can have a "work" branch to develop in, a "test" branch where the code or + change is tested, a "stage" branch where changes are ready to be committed, and so forth. + As your project develops, you can merge code across the branches to reflect ever-increasing + stable states of the development.</para></listitem> + <listitem><para><emphasis>Use Push and Pull:</emphasis> The push-pull workflow is based on the + concept of developers "pushing" local commits to a remote repository, which is + usually a contribution repository. + This workflow is also based on developers "pulling" known states of the project down into their + local development repositories. + The workflow easily allows you to pull changes submitted by other developers from the + upstream repository into your work area ensuring that you have the most recent software + on which to develop. + The Yocto Project has two scripts named <filename>create-pull-request</filename> and + <filename>send-pull-request</filename> that ship with the release to facilitate this + workflow. + You can find these scripts in the <filename>scripts</filename> + folder of the + <link linkend='source-directory'>Source Directory</link>. + For information on how to use these scripts, see the + "<link linkend='pushing-a-change-upstream'>Using Scripts to Push a Change Upstream and Request a Pull</link>" section. + </para></listitem> + <listitem><para><emphasis>Patch Workflow:</emphasis> This workflow allows you to notify the + maintainer through an email that you have a change (or patch) you would like considered + for the "master" branch of the Git repository. + To send this type of change, you format the patch and then send the email using the Git commands + <filename>git format-patch</filename> and <filename>git send-email</filename>. + For information on how to use these scripts, see the + "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + section. + </para></listitem> + </itemizedlist> + </para> +</section> + +<section id='tracking-bugs'> + <title>Tracking Bugs</title> + + <para> + The Yocto Project uses its own implementation of + <ulink url='http://www.bugzilla.org/about/'>Bugzilla</ulink> to track bugs. + Implementations of Bugzilla work well for group development because they track bugs and code + changes, can be used to communicate changes and problems with developers, can be used to + submit and review patches, and can be used to manage quality assurance. + The home page for the Yocto Project implementation of Bugzilla is + <ulink url='&YOCTO_BUGZILLA_URL;'>&YOCTO_BUGZILLA_URL;</ulink>. + </para> + + <para> + Sometimes it is helpful to submit, investigate, or track a bug against the Yocto Project itself + such as when discovering an issue with some component of the build system that acts contrary + to the documentation or your expectations. + Following is the general procedure for submitting a new bug using the Yocto Project + Bugzilla. + You can find more information on defect management, bug tracking, and feature request + processes all accomplished through the Yocto Project Bugzilla on the + <ulink url='&YOCTO_WIKI_URL;/wiki/Bugzilla_Configuration_and_Bug_Tracking'>wiki page</ulink>. + <orderedlist> + <listitem><para>Always use the Yocto Project implementation of Bugzilla to submit + a bug.</para></listitem> + <listitem><para>When submitting a new bug, be sure to choose the appropriate + Classification, Product, and Component for which the issue was found. + Defects for the Yocto Project fall into one of seven classifications: + Yocto Project Components, Infrastructure, Build System & Metadata, + Documentation, QA/Testing, Runtime and Hardware. + Each of these Classifications break down into multiple Products and, in some + cases, multiple Components.</para></listitem> + <listitem><para>Use the bug form to choose the correct Hardware and Architecture + for which the bug applies.</para></listitem> + <listitem><para>Indicate the Yocto Project version you were using when the issue + occurred.</para></listitem> + <listitem><para>Be sure to indicate the Severity of the bug. + Severity communicates how the bug impacted your work.</para></listitem> + <listitem><para>Select the appropriate "Documentation change" item + for the bug. + Fixing a bug may or may not affect the Yocto Project + documentation.</para></listitem> + <listitem><para>Provide a brief summary of the issue. + Try to limit your summary to just a line or two and be sure to capture the + essence of the issue.</para></listitem> + <listitem><para>Provide a detailed description of the issue. + You should provide as much detail as you can about the context, behavior, output, + and so forth that surrounds the issue. + You can even attach supporting files for output from logs by + using the "Add an attachment" button.</para></listitem> + <listitem><para>Be sure to copy the appropriate people in the + "CC List" for the bug. + See the "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + section for information about finding out who is responsible + for code.</para></listitem> + <listitem><para>Submit the bug by clicking the "Submit Bug" button.</para></listitem> + </orderedlist> + </para> +</section> + +<section id='how-to-submit-a-change'> + <title>How to Submit a Change</title> + + <para> + Contributions to the Yocto Project and OpenEmbedded are very welcome. + Because the system is extremely configurable and flexible, we recognize that developers + will want to extend, configure or optimize it for their specific uses. + You should send patches to the appropriate mailing list so that they + can be reviewed and merged by the appropriate maintainer. + </para> + + <para> + Before submitting any change, be sure to find out who you should be + notifying. + Several methods exist through which you find out who you should be copying + or notifying: + <itemizedlist> + <listitem><para><emphasis>Maintenance File:</emphasis> + Examine the <filename>maintainers.inc</filename> file, which is + located in the + <link linkend='source-directory'>Source Directory</link> + at <filename>meta-poky/conf/distro/include</filename>, to + see who is responsible for code. + </para></listitem> + <listitem><para><emphasis>Board Support Package (BSP) README Files:</emphasis> + For BSP maintainers of supported BSPs, you can examine + individual BSP <filename>README</filename> files. + In addition, some layers (such as the <filename>meta-intel</filename> layer), + include a <filename>MAINTAINERS</filename> file which contains + a list of all supported BSP maintainers for that layer. + </para></listitem> + <listitem><para><emphasis>Search by File:</emphasis> + Using <link linkend='git'>Git</link>, you can enter the + following command to bring up a short list of all commits + against a specific file: + <literallayout class='monospaced'> + git shortlog -- <replaceable>filename</replaceable> + </literallayout> + Just provide the name of the file for which you are interested. + The information returned is not ordered by history but does + include a list of all committers grouped by name. + From the list, you can see who is responsible for the bulk of + the changes against the file. + </para></listitem> + </itemizedlist> + </para> + + <para> + For a list of the Yocto Project and related mailing lists, see the + "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing lists</ulink>" section in + the Yocto Project Reference Manual. + </para> + + <para> + Here is some guidance on which mailing list to use for what type of change: + <itemizedlist> + <listitem><para>For changes to the core + <link linkend='metadata'>Metadata</link>, send your patch to the + <ulink url='&OE_LISTS_URL;/listinfo/openembedded-core'>openembedded-core</ulink> mailing list. + For example, a change to anything under the <filename>meta</filename> or + <filename>scripts</filename> directories + should be sent to this mailing list.</para></listitem> + <listitem><para>For changes to BitBake (anything under the <filename>bitbake</filename> + directory), send your patch to the + <ulink url='&OE_LISTS_URL;/listinfo/bitbake-devel'>bitbake-devel</ulink> mailing list.</para></listitem> + <listitem><para>For changes to <filename>meta-poky</filename>, send your patch to the + <ulink url='&YOCTO_LISTS_URL;/listinfo/poky'>poky</ulink> mailing list.</para></listitem> + <listitem><para>For changes to other layers hosted on + <filename>yoctoproject.org</filename> (unless the + layer's documentation specifies otherwise), tools, and Yocto Project + documentation, use the + <ulink url='&YOCTO_LISTS_URL;/listinfo/yocto'>yocto</ulink> mailing list.</para></listitem> + <listitem><para>For additional recipes that do not fit into the core Metadata, + you should determine which layer the recipe should go into and submit the + change in the manner recommended by the documentation (e.g. README) supplied + with the layer. If in doubt, please ask on the + <ulink url='&YOCTO_LISTS_URL;/listinfo/yocto'>yocto</ulink> or + <ulink url='&OE_LISTS_URL;/listinfo/openembedded-devel'>openembedded-devel</ulink> + mailing lists.</para></listitem> + </itemizedlist> + </para> + + <para> + When you send a patch, be sure to include a "Signed-off-by:" + line in the same style as required by the Linux kernel. + Adding this line signifies that you, the submitter, have agreed to the Developer's Certificate of Origin 1.1 + as follows: + <literallayout class='monospaced'> + Developer's Certificate of Origin 1.1 + + By making a contribution to this project, I certify that: + + (a) The contribution was created in whole or in part by me and I + have the right to submit it under the open source license + indicated in the file; or + + (b) The contribution is based upon previous work that, to the best + of my knowledge, is covered under an appropriate open source + license and I have the right under that license to submit that + work with modifications, whether created in whole or in part + by me, under the same open source license (unless I am + permitted to submit under a different license), as indicated + in the file; or + + (c) The contribution was provided directly to me by some other + person who certified (a), (b) or (c) and I have not modified + it. + + (d) I understand and agree that this project and the contribution + are public and that a record of the contribution (including all + personal information I submit with it, including my sign-off) is + maintained indefinitely and may be redistributed consistent with + this project or the open source license(s) involved. + </literallayout> + </para> + + <para> + In a collaborative environment, it is necessary to have some sort of standard + or method through which you submit changes. + Otherwise, things could get quite chaotic. + One general practice to follow is to make small, controlled changes. + Keeping changes small and isolated aids review, makes merging/rebasing easier + and keeps the change history clean when anyone needs to refer to it in future. + </para> + + <para> + When you make a commit, you must follow certain standards established by the + OpenEmbedded and Yocto Project development teams. + For each commit, you must provide a single-line summary of the change and you + should almost always provide a more detailed description of what you did (i.e. + the body of the commit message). + The only exceptions for not providing a detailed description would be if your + change is a simple, self-explanatory change that needs no further description + beyond the summary. + Here are the guidelines for composing a commit message: + <itemizedlist> + <listitem><para>Provide a single-line, short summary of the change. + This summary is typically viewable in the "shortlist" of changes. + Thus, providing something short and descriptive that gives the reader + a summary of the change is useful when viewing a list of many commits. + This short description should be prefixed by the recipe name (if changing a recipe), or + else the short form path to the file being changed. + </para></listitem> + <listitem><para>For the body of the commit message, provide detailed information + that describes what you changed, why you made the change, and the approach + you used. It may also be helpful if you mention how you tested the change. + Provide as much detail as you can in the body of the commit message. + </para></listitem> + <listitem><para> + If the change addresses a specific bug or issue that is + associated with a bug-tracking ID, include a reference to that + ID in your detailed description. + For example, the Yocto Project uses a specific convention for + bug references - any commit that addresses a specific bug should + use the following form for the detailed description: + <literallayout class='monospaced'> + Fixes [YOCTO #<replaceable>bug-id</replaceable>] + + <replaceable>detailed description of change</replaceable> + </literallayout></para></listitem> + Where <replaceable>bug-id</replaceable> is replaced with the + specific bug ID from the Yocto Project Bugzilla instance. + </itemizedlist> + </para> + + <para> + You can find more guidance on creating well-formed commit messages at this OpenEmbedded + wiki page: + <ulink url='&OE_HOME_URL;/wiki/Commit_Patch_Message_Guidelines'></ulink>. + </para> + + <para> + The next two sections describe general instructions for both pushing + changes upstream and for submitting changes as patches. + </para> + + <section id='pushing-a-change-upstream'> + <title>Using Scripts to Push a Change Upstream and Request a Pull</title> + + <para> + The basic flow for pushing a change to an upstream "contrib" Git repository is as follows: + <itemizedlist> + <listitem><para>Make your changes in your local Git repository.</para></listitem> + <listitem><para>Stage your changes by using the <filename>git add</filename> + command on each file you changed.</para></listitem> + <listitem><para> + Commit the change by using the + <filename>git commit</filename> command. + Be sure to provide a commit message that follows the + project’s commit message standards as described earlier. + </para></listitem> + <listitem><para> + Push the change to the upstream "contrib" repository by + using the <filename>git push</filename> command. + </para></listitem> + <listitem><para>Notify the maintainer that you have pushed a change by making a pull + request. + The Yocto Project provides two scripts that conveniently let you generate and send + pull requests to the Yocto Project. + These scripts are <filename>create-pull-request</filename> and + <filename>send-pull-request</filename>. + You can find these scripts in the <filename>scripts</filename> directory + within the <link linkend='source-directory'>Source Directory</link>.</para> + <para>Using these scripts correctly formats the requests without introducing any + whitespace or HTML formatting. + The maintainer that receives your patches needs to be able to save and apply them + directly from your emails. + Using these scripts is the preferred method for sending patches.</para> + <para>For help on using these scripts, simply provide the + <filename>-h</filename> argument as follows: + <literallayout class='monospaced'> + $ poky/scripts/create-pull-request -h + $ poky/scripts/send-pull-request -h + </literallayout></para></listitem> + </itemizedlist> + </para> + + <para> + You can find general Git information on how to push a change upstream in the + <ulink url='http://git-scm.com/book/en/v2/Distributed-Git-Distributed-Workflows'>Git Community Book</ulink>. + </para> + </section> + + <section id='submitting-a-patch'> + <title>Using Email to Submit a Patch</title> + + <para> + You can submit patches without using the <filename>create-pull-request</filename> and + <filename>send-pull-request</filename> scripts described in the previous section. + However, keep in mind, the preferred method is to use the scripts. + </para> + + <para> + Depending on the components changed, you need to submit the email to a specific + mailing list. + For some guidance on which mailing list to use, see the list in the + "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + section. + For a description of the available mailing lists, see the + "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing Lists</ulink>" + section in the Yocto Project Reference Manual. + </para> + + <para> + Here is the general procedure on how to submit a patch through email without using the + scripts: + <itemizedlist> + <listitem><para>Make your changes in your local Git repository.</para></listitem> + <listitem><para>Stage your changes by using the <filename>git add</filename> + command on each file you changed.</para></listitem> + <listitem><para>Commit the change by using the + <filename>git commit --signoff</filename> command. + Using the <filename>--signoff</filename> option identifies you as the person + making the change and also satisfies the Developer's Certificate of + Origin (DCO) shown earlier.</para> + <para>When you form a commit, you must follow certain standards established by the + Yocto Project development team. + See the earlier section + "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" + for Yocto Project commit message standards.</para></listitem> + <listitem><para>Format the commit into an email message. + To format commits, use the <filename>git format-patch</filename> command. + When you provide the command, you must include a revision list or a number of patches + as part of the command. + For example, either of these two commands takes your most + recent single commit and formats it as an email message in + the current directory: + <literallayout class='monospaced'> + $ git format-patch -1 + </literallayout> + or + <literallayout class='monospaced'> + $ git format-patch HEAD~ + </literallayout></para> + <para>After the command is run, the current directory contains a + numbered <filename>.patch</filename> file for the commit.</para> + <para>If you provide several commits as part of the command, + the <filename>git format-patch</filename> command produces a + series of numbered files in the current directory – one for each commit. + If you have more than one patch, you should also use the + <filename>--cover</filename> option with the command, which generates a + cover letter as the first "patch" in the series. + You can then edit the cover letter to provide a description for + the series of patches. + For information on the <filename>git format-patch</filename> command, + see <filename>GIT_FORMAT_PATCH(1)</filename> displayed using the + <filename>man git-format-patch</filename> command.</para> + <note>If you are or will be a frequent contributor to the Yocto Project + or to OpenEmbedded, you might consider requesting a contrib area and the + necessary associated rights.</note></listitem> + <listitem><para>Import the files into your mail client by using the + <filename>git send-email</filename> command. + <note>In order to use <filename>git send-email</filename>, you must have the + the proper Git packages installed. + For Ubuntu, Debian, and Fedora the package is <filename>git-email</filename>.</note></para> + <para>The <filename>git send-email</filename> command sends email by using a local + or remote Mail Transport Agent (MTA) such as + <filename>msmtp</filename>, <filename>sendmail</filename>, or through a direct + <filename>smtp</filename> configuration in your Git <filename>config</filename> + file. + If you are submitting patches through email only, it is very important + that you submit them without any whitespace or HTML formatting that + either you or your mailer introduces. + The maintainer that receives your patches needs to be able to save and + apply them directly from your emails. + A good way to verify that what you are sending will be applicable by the + maintainer is to do a dry run and send them to yourself and then + save and apply them as the maintainer would.</para> + <para>The <filename>git send-email</filename> command is the preferred method + for sending your patches since there is no risk of compromising whitespace + in the body of the message, which can occur when you use your own mail client. + The command also has several options that let you + specify recipients and perform further editing of the email message. + For information on how to use the <filename>git send-email</filename> command, + see <filename>GIT-SEND-EMAIL(1)</filename> displayed using + the <filename>man git-send-email</filename> command. + </para></listitem> + </itemizedlist> + </para> + </section> +</section> +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> |
