1776 lines
86 KiB
XML
1776 lines
86 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='technical-details'>
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<title>Technical Details</title>
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<para>
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This chapter provides technical details for various parts of the
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Yocto Project.
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Currently, topics include Yocto Project components,
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cross-toolchain generation, shared state (sstate) cache,
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x32, Wayland support, and Licenses.
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</para>
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<section id='usingpoky-components'>
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<title>Yocto Project Components</title>
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<para>
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The
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<ulink url='&YOCTO_DOCS_DEV_URL;#bitbake-term'>BitBake</ulink>
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task executor together with various types of configuration files form
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the OpenEmbedded Core.
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This section overviews these components by describing their use and
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how they interact.
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</para>
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<para>
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BitBake handles the parsing and execution of the data files.
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The data itself is of various types:
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<itemizedlist>
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<listitem><para><emphasis>Recipes:</emphasis> Provides details
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about particular pieces of software.
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</para></listitem>
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<listitem><para><emphasis>Class Data:</emphasis> Abstracts
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common build information (e.g. how to build a Linux kernel).
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</para></listitem>
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<listitem><para><emphasis>Configuration Data:</emphasis> Defines
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machine-specific settings, policy decisions, and so forth.
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Configuration data acts as the glue to bind everything
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together.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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BitBake knows how to combine multiple data sources together and refers
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to each data source as a layer.
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For information on layers, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and
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Creating Layers</ulink>" section of the Yocto Project Development Manual.
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</para>
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<para>
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Following are some brief details on these core components.
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For additional information on how these components interact during
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a build, see the
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"<link linkend='closer-look'>A Closer Look at the Yocto Project Development Environment</link>"
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Chapter.
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</para>
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<section id='usingpoky-components-bitbake'>
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<title>BitBake</title>
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<para>
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BitBake is the tool at the heart of the OpenEmbedded build system
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and is responsible for parsing the
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<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>,
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generating a list of tasks from it, and then executing those tasks.
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</para>
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<para>
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This section briefly introduces BitBake.
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If you want more information on BitBake, see the
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<ulink url='&YOCTO_DOCS_BB_URL;#bitbake-user-manual'>BitBake User Manual</ulink>.
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</para>
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<para>
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To see a list of the options BitBake supports, use either of
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the following commands:
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<literallayout class='monospaced'>
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$ bitbake -h
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$ bitbake --help
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</literallayout>
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</para>
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<para>
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The most common usage for BitBake is <filename>bitbake <replaceable>packagename</replaceable></filename>, where
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<filename>packagename</filename> is the name of the package you want to build
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(referred to as the "target" in this manual).
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The target often equates to the first part of a recipe's filename
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(e.g. "foo" for a recipe named
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<filename>foo_1.3.0-r0.bb</filename>).
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So, to process the <filename>matchbox-desktop_1.2.3.bb</filename> recipe file, you
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might type the following:
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<literallayout class='monospaced'>
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$ bitbake matchbox-desktop
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</literallayout>
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Several different versions of <filename>matchbox-desktop</filename> might exist.
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BitBake chooses the one selected by the distribution configuration.
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You can get more details about how BitBake chooses between different
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target versions and providers in the
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"<ulink url='&YOCTO_DOCS_BB_URL;#bb-bitbake-preferences'>Preferences</ulink>"
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section of the BitBake User Manual.
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</para>
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<para>
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BitBake also tries to execute any dependent tasks first.
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So for example, before building <filename>matchbox-desktop</filename>, BitBake
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would build a cross compiler and <filename>glibc</filename> if they had not already
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been built.
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</para>
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<para>
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A useful BitBake option to consider is the <filename>-k</filename> or
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<filename>--continue</filename> option.
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This option instructs BitBake to try and continue processing the job
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as long as possible even after encountering an error.
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When an error occurs, the target that
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failed and those that depend on it cannot be remade.
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However, when you use this option other dependencies can still be
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processed.
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</para>
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</section>
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<section id='usingpoky-components-metadata'>
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<title>Metadata (Recipes)</title>
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<para>
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Files that have the <filename>.bb</filename> suffix are "recipes"
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files.
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In general, a recipe contains information about a single piece of
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software.
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This information includes the location from which to download the
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unaltered source, any source patches to be applied to that source
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(if needed), which special configuration options to apply,
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how to compile the source files, and how to package the compiled
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output.
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</para>
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<para>
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The term "package" is sometimes used to refer to recipes. However,
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since the word "package" is used for the packaged output from the OpenEmbedded
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build system (i.e. <filename>.ipk</filename> or <filename>.deb</filename> files),
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this document avoids using the term "package" when referring to recipes.
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</para>
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</section>
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<section id='usingpoky-components-classes'>
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<title>Classes</title>
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<para>
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Class files (<filename>.bbclass</filename>) contain information that
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is useful to share between
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<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink> files.
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An example is the
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<link linkend='ref-classes-autotools'><filename>autotools</filename></link>
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class, which contains common settings for any application that
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Autotools uses.
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The "<link linkend='ref-classes'>Classes</link>" chapter provides
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details about classes and how to use them.
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</para>
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</section>
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<section id='usingpoky-components-configuration'>
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<title>Configuration</title>
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<para>
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The configuration files (<filename>.conf</filename>) define various configuration variables
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that govern the OpenEmbedded build process.
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These files fall into several areas that define machine configuration options,
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distribution configuration options, compiler tuning options, general common configuration
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options, and user configuration options in <filename>local.conf</filename>, which is found
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in the
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<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
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</para>
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</section>
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</section>
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<section id="cross-development-toolchain-generation">
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<title>Cross-Development Toolchain Generation</title>
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<para>
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The Yocto Project does most of the work for you when it comes to
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creating
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<ulink url='&YOCTO_DOCS_DEV_URL;#cross-development-toolchain'>cross-development toolchains</ulink>.
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This section provides some technical background on how
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cross-development toolchains are created and used.
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For more information on toolchains, you can also see the
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<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>.
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</para>
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<para>
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In the Yocto Project development environment, cross-development
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toolchains are used to build the image and applications that run on the
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target hardware.
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With just a few commands, the OpenEmbedded build system creates
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these necessary toolchains for you.
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</para>
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<para>
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The following figure shows a high-level build environment regarding
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toolchain construction and use.
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</para>
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<para>
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<imagedata fileref="figures/cross-development-toolchains.png" width="8in" depth="6in" align="center" />
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</para>
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<para>
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Most of the work occurs on the Build Host.
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This is the machine used to build images and generally work within the
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the Yocto Project environment.
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When you run BitBake to create an image, the OpenEmbedded build system
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uses the host <filename>gcc</filename> compiler to bootstrap a
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cross-compiler named <filename>gcc-cross</filename>.
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The <filename>gcc-cross</filename> compiler is what BitBake uses to
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compile source files when creating the target image.
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You can think of <filename>gcc-cross</filename> simply as an
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automatically generated cross-compiler that is used internally within
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BitBake only.
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<note>
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The extensible SDK does not use
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<filename>gcc-cross-canadian</filename> since this SDK
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ships a copy of the OpenEmbedded build system and the sysroot
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within it contains <filename>gcc-cross</filename>.
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</note>
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</para>
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<para>
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The chain of events that occurs when <filename>gcc-cross</filename> is
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bootstrapped is as follows:
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<literallayout class='monospaced'>
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gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> glibc-initial -> glibc -> gcc-cross -> gcc-runtime
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</literallayout>
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<itemizedlist>
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<listitem><para><filename>gcc</filename>:
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The build host's GNU Compiler Collection (GCC).
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</para></listitem>
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<listitem><para><filename>binutils-cross</filename>:
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The bare minimum binary utilities needed in order to run
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the <filename>gcc-cross-initial</filename> phase of the
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bootstrap operation.
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</para></listitem>
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<listitem><para><filename>gcc-cross-initial</filename>:
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An early stage of the bootstrap process for creating
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the cross-compiler.
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This stage builds enough of the <filename>gcc-cross</filename>,
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the C library, and other pieces needed to finish building the
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final cross-compiler in later stages.
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This tool is a "native" package (i.e. it is designed to run on
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the build host).
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</para></listitem>
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<listitem><para><filename>linux-libc-headers</filename>:
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Headers needed for the cross-compiler.
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</para></listitem>
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<listitem><para><filename>glibc-initial</filename>:
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An initial version of the Embedded GLIBC needed to bootstrap
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<filename>glibc</filename>.
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</para></listitem>
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<listitem><para><filename>gcc-cross</filename>:
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The final stage of the bootstrap process for the
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cross-compiler.
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This stage results in the actual cross-compiler that
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BitBake uses when it builds an image for a targeted
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device.
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<note>
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If you are replacing this cross compiler toolchain
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with a custom version, you must replace
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<filename>gcc-cross</filename>.
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</note>
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This tool is also a "native" package (i.e. it is
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designed to run on the build host).
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</para></listitem>
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<listitem><para><filename>gcc-runtime</filename>:
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Runtime libraries resulting from the toolchain bootstrapping
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process.
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This tool produces a binary that consists of the
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runtime libraries need for the targeted device.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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You can use the OpenEmbedded build system to build an installer for
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the relocatable SDK used to develop applications.
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When you run the installer, it installs the toolchain, which contains
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the development tools (e.g., the
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<filename>gcc-cross-canadian</filename>),
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<filename>binutils-cross-canadian</filename>, and other
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<filename>nativesdk-*</filename> tools,
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which are tools native to the SDK (i.e. native to
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<link linkend='var-SDK_ARCH'><filename>SDK_ARCH</filename></link>),
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you need to cross-compile and test your software.
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The figure shows the commands you use to easily build out this
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toolchain.
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This cross-development toolchain is built to execute on the
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<link linkend='var-SDKMACHINE'><filename>SDKMACHINE</filename></link>,
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which might or might not be the same
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machine as the Build Host.
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<note>
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If your target architecture is supported by the Yocto Project,
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you can take advantage of pre-built images that ship with the
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Yocto Project and already contain cross-development toolchain
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installers.
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</note>
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</para>
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<para>
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Here is the bootstrap process for the relocatable toolchain:
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<literallayout class='monospaced'>
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gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers ->
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glibc-initial -> nativesdk-glibc -> gcc-crosssdk -> gcc-cross-canadian
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</literallayout>
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<itemizedlist>
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<listitem><para><filename>gcc</filename>:
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The build host's GNU Compiler Collection (GCC).
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</para></listitem>
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<listitem><para><filename>binutils-crosssdk</filename>:
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The bare minimum binary utilities needed in order to run
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the <filename>gcc-crosssdk-initial</filename> phase of the
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bootstrap operation.
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</para></listitem>
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<listitem><para><filename>gcc-crosssdk-initial</filename>:
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An early stage of the bootstrap process for creating
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the cross-compiler.
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This stage builds enough of the
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<filename>gcc-crosssdk</filename> and supporting pieces so that
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the final stage of the bootstrap process can produce the
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finished cross-compiler.
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This tool is a "native" binary that runs on the build host.
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</para></listitem>
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<listitem><para><filename>linux-libc-headers</filename>:
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Headers needed for the cross-compiler.
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</para></listitem>
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<listitem><para><filename>glibc-initial</filename>:
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An initial version of the Embedded GLIBC needed to bootstrap
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<filename>nativesdk-glibc</filename>.
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</para></listitem>
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<listitem><para><filename>nativesdk-glibc</filename>:
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The Embedded GLIBC needed to bootstrap the
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<filename>gcc-crosssdk</filename>.
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</para></listitem>
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<listitem><para><filename>gcc-crosssdk</filename>:
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The final stage of the bootstrap process for the
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relocatable cross-compiler.
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The <filename>gcc-crosssdk</filename> is a transitory compiler
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and never leaves the build host.
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Its purpose is to help in the bootstrap process to create the
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eventual relocatable <filename>gcc-cross-canadian</filename>
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compiler, which is relocatable.
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This tool is also a "native" package (i.e. it is
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designed to run on the build host).
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</para></listitem>
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<listitem><para><filename>gcc-cross-canadian</filename>:
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The final relocatable cross-compiler.
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When run on the
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<link linkend='var-SDKMACHINE'><filename>SDKMACHINE</filename></link>,
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this tool
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produces executable code that runs on the target device.
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Only one cross-canadian compiler is produced per architecture
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since they can be targeted at different processor optimizations
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using configurations passed to the compiler through the
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compile commands.
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This circumvents the need for multiple compilers and thus
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reduces the size of the toolchains.
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</para></listitem>
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</itemizedlist>
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</para>
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<note>
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For information on advantages gained when building a
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cross-development toolchain installer, see the
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"<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-building-an-sdk-installer'>Building an SDK Installer</ulink>"
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section in the Yocto Project Software Development Kit (SDK) Developer's
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Guide.
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</note>
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</section>
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<section id="shared-state-cache">
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<title>Shared State Cache</title>
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<para>
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By design, the OpenEmbedded build system builds everything from scratch unless
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BitBake can determine that parts do not need to be rebuilt.
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Fundamentally, building from scratch is attractive as it means all parts are
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built fresh and there is no possibility of stale data causing problems.
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When developers hit problems, they typically default back to building from scratch
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so they know the state of things from the start.
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</para>
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<para>
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Building an image from scratch is both an advantage and a disadvantage to the process.
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As mentioned in the previous paragraph, building from scratch ensures that
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everything is current and starts from a known state.
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However, building from scratch also takes much longer as it generally means
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rebuilding things that do not necessarily need to be rebuilt.
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</para>
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<para>
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The Yocto Project implements shared state code that supports incremental builds.
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The implementation of the shared state code answers the following questions that
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were fundamental roadblocks within the OpenEmbedded incremental build support system:
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<itemizedlist>
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<listitem><para>What pieces of the system have changed and what pieces have
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not changed?</para></listitem>
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<listitem><para>How are changed pieces of software removed and replaced?</para></listitem>
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<listitem><para>How are pre-built components that do not need to be rebuilt from scratch
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used when they are available?</para></listitem>
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</itemizedlist>
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</para>
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<para>
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For the first question, the build system detects changes in the "inputs" to a given task by
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creating a checksum (or signature) of the task's inputs.
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If the checksum changes, the system assumes the inputs have changed and the task needs to be
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rerun.
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For the second question, the shared state (sstate) code tracks which tasks add which output
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to the build process.
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This means the output from a given task can be removed, upgraded or otherwise manipulated.
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The third question is partly addressed by the solution for the second question
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assuming the build system can fetch the sstate objects from remote locations and
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install them if they are deemed to be valid.
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</para>
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|
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<note>
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The OpenEmbedded build system does not maintain
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<link linkend='var-PR'><filename>PR</filename></link> information
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as part of the shared state packages.
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Consequently, considerations exist that affect maintaining shared
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state feeds.
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For information on how the OpenEmbedded build system
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works with packages and can
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track incrementing <filename>PR</filename> information, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#automatically-incrementing-a-binary-package-revision-number'>Automatically Incrementing a Binary Package Revision Number</ulink>"
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section.
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</note>
|
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<para>
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The rest of this section goes into detail about the overall incremental build
|
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architecture, the checksums (signatures), shared state, and some tips and tricks.
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|
</para>
|
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|
|
<section id='overall-architecture'>
|
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<title>Overall Architecture</title>
|
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|
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<para>
|
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When determining what parts of the system need to be built, BitBake
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works on a per-task basis rather than a per-recipe basis.
|
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You might wonder why using a per-task basis is preferred over a per-recipe basis.
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To help explain, consider having the IPK packaging backend enabled and then switching to DEB.
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In this case, the
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<link linkend='ref-tasks-install'><filename>do_install</filename></link>
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and
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<link linkend='ref-tasks-package'><filename>do_package</filename></link>
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task outputs are still valid.
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However, with a per-recipe approach, the build would not include the
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<filename>.deb</filename> files.
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Consequently, you would have to invalidate the whole build and rerun it.
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Rerunning everything is not the best solution.
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Also, in this case, the core must be "taught" much about specific tasks.
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This methodology does not scale well and does not allow users to easily add new tasks
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in layers or as external recipes without touching the packaged-staging core.
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</para>
|
|
</section>
|
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|
|
<section id='checksums'>
|
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<title>Checksums (Signatures)</title>
|
|
|
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<para>
|
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The shared state code uses a checksum, which is a unique signature of a task's
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inputs, to determine if a task needs to be run again.
|
|
Because it is a change in a task's inputs that triggers a rerun, the process
|
|
needs to detect all the inputs to a given task.
|
|
For shell tasks, this turns out to be fairly easy because
|
|
the build process generates a "run" shell script for each task and
|
|
it is possible to create a checksum that gives you a good idea of when
|
|
the task's data changes.
|
|
</para>
|
|
|
|
<para>
|
|
To complicate the problem, there are things that should not be
|
|
included in the checksum.
|
|
First, there is the actual specific build path of a given task -
|
|
the <link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>.
|
|
It does not matter if the work directory changes because it should
|
|
not affect the output for target packages.
|
|
Also, the build process has the objective of making native
|
|
or cross packages relocatable.
|
|
<note>
|
|
Both native and cross packages run on the build host.
|
|
However, cross packages generate output for the target
|
|
architecture.
|
|
</note>
|
|
The checksum therefore needs to exclude
|
|
<filename>WORKDIR</filename>.
|
|
The simplistic approach for excluding the work directory is to set
|
|
<filename>WORKDIR</filename> to some fixed value and create the
|
|
checksum for the "run" script.
|
|
</para>
|
|
|
|
<para>
|
|
Another problem results from the "run" scripts containing functions that
|
|
might or might not get called.
|
|
The incremental build solution contains code that figures out dependencies
|
|
between shell functions.
|
|
This code is used to prune the "run" scripts down to the minimum set,
|
|
thereby alleviating this problem and making the "run" scripts much more
|
|
readable as a bonus.
|
|
</para>
|
|
|
|
<para>
|
|
So far we have solutions for shell scripts.
|
|
What about Python tasks?
|
|
The same approach applies even though these tasks are more difficult.
|
|
The process needs to figure out what variables a Python function accesses
|
|
and what functions it calls.
|
|
Again, the incremental build solution contains code that first figures out
|
|
the variable and function dependencies, and then creates a checksum for the data
|
|
used as the input to the task.
|
|
</para>
|
|
|
|
<para>
|
|
Like the <filename>WORKDIR</filename> case, situations exist where dependencies
|
|
should be ignored.
|
|
For these cases, you can instruct the build process to ignore a dependency
|
|
by using a line like the following:
|
|
<literallayout class='monospaced'>
|
|
PACKAGE_ARCHS[vardepsexclude] = "MACHINE"
|
|
</literallayout>
|
|
This example ensures that the
|
|
<link linkend='var-PACKAGE_ARCHS'><filename>PACKAGE_ARCHS</filename></link>
|
|
variable does not
|
|
depend on the value of
|
|
<link linkend='var-MACHINE'><filename>MACHINE</filename></link>,
|
|
even if it does reference it.
|
|
</para>
|
|
|
|
<para>
|
|
Equally, there are cases where we need to add dependencies BitBake is not able to find.
|
|
You can accomplish this by using a line like the following:
|
|
<literallayout class='monospaced'>
|
|
PACKAGE_ARCHS[vardeps] = "MACHINE"
|
|
</literallayout>
|
|
This example explicitly adds the <filename>MACHINE</filename> variable as a
|
|
dependency for <filename>PACKAGE_ARCHS</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
Consider a case with in-line Python, for example, where BitBake is not
|
|
able to figure out dependencies.
|
|
When running in debug mode (i.e. using <filename>-DDD</filename>), BitBake
|
|
produces output when it discovers something for which it cannot figure out
|
|
dependencies.
|
|
The Yocto Project team has currently not managed to cover those dependencies
|
|
in detail and is aware of the need to fix this situation.
|
|
</para>
|
|
|
|
<para>
|
|
Thus far, this section has limited discussion to the direct inputs into a task.
|
|
Information based on direct inputs is referred to as the "basehash" in the
|
|
code.
|
|
However, there is still the question of a task's indirect inputs - the
|
|
things that were already built and present in the
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
|
|
The checksum (or signature) for a particular task needs to add the hashes
|
|
of all the tasks on which the particular task depends.
|
|
Choosing which dependencies to add is a policy decision.
|
|
However, the effect is to generate a master checksum that combines the basehash
|
|
and the hashes of the task's dependencies.
|
|
</para>
|
|
|
|
<para>
|
|
At the code level, there are a variety of ways both the basehash and the
|
|
dependent task hashes can be influenced.
|
|
Within the BitBake configuration file, we can give BitBake some extra information
|
|
to help it construct the basehash.
|
|
The following statement effectively results in a list of global variable
|
|
dependency excludes - variables never included in any checksum:
|
|
<literallayout class='monospaced'>
|
|
BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH DL_DIR \
|
|
SSTATE_DIR THISDIR FILESEXTRAPATHS FILE_DIRNAME HOME LOGNAME SHELL TERM \
|
|
USER FILESPATH STAGING_DIR_HOST STAGING_DIR_TARGET COREBASE PRSERV_HOST \
|
|
PRSERV_DUMPDIR PRSERV_DUMPFILE PRSERV_LOCKDOWN PARALLEL_MAKE \
|
|
CCACHE_DIR EXTERNAL_TOOLCHAIN CCACHE CCACHE_DISABLE LICENSE_PATH SDKPKGSUFFIX"
|
|
</literallayout>
|
|
The previous example excludes
|
|
<link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>
|
|
since that variable is actually constructed as a path within
|
|
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>, which is on
|
|
the whitelist.
|
|
</para>
|
|
|
|
<para>
|
|
The rules for deciding which hashes of dependent tasks to include through
|
|
dependency chains are more complex and are generally accomplished with a
|
|
Python function.
|
|
The code in <filename>meta/lib/oe/sstatesig.py</filename> shows two examples
|
|
of this and also illustrates how you can insert your own policy into the system
|
|
if so desired.
|
|
This file defines the two basic signature generators <filename>OE-Core</filename>
|
|
uses: "OEBasic" and "OEBasicHash".
|
|
By default, there is a dummy "noop" signature handler enabled in BitBake.
|
|
This means that behavior is unchanged from previous versions.
|
|
<filename>OE-Core</filename> uses the "OEBasicHash" signature handler by default
|
|
through this setting in the <filename>bitbake.conf</filename> file:
|
|
<literallayout class='monospaced'>
|
|
BB_SIGNATURE_HANDLER ?= "OEBasicHash"
|
|
</literallayout>
|
|
The "OEBasicHash" <filename>BB_SIGNATURE_HANDLER</filename> is the same as the
|
|
"OEBasic" version but adds the task hash to the stamp files.
|
|
This results in any
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>
|
|
change that changes the task hash, automatically
|
|
causing the task to be run again.
|
|
This removes the need to bump <link linkend='var-PR'><filename>PR</filename></link>
|
|
values, and changes to Metadata automatically ripple across the build.
|
|
</para>
|
|
|
|
<para>
|
|
It is also worth noting that the end result of these signature generators is to
|
|
make some dependency and hash information available to the build.
|
|
This information includes:
|
|
<itemizedlist>
|
|
<listitem><para><filename>BB_BASEHASH_task-</filename><replaceable>taskname</replaceable>:
|
|
The base hashes for each task in the recipe.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_BASEHASH_</filename><replaceable>filename</replaceable><filename>:</filename><replaceable>taskname</replaceable>:
|
|
The base hashes for each dependent task.
|
|
</para></listitem>
|
|
<listitem><para><filename>BBHASHDEPS_</filename><replaceable>filename</replaceable><filename>:</filename><replaceable>taskname</replaceable>:
|
|
The task dependencies for each task.
|
|
</para></listitem>
|
|
<listitem><para><filename>BB_TASKHASH</filename>:
|
|
The hash of the currently running task.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='shared-state'>
|
|
<title>Shared State</title>
|
|
|
|
<para>
|
|
Checksums and dependencies, as discussed in the previous section, solve half the
|
|
problem of supporting a shared state.
|
|
The other part of the problem is being able to use checksum information during the build
|
|
and being able to reuse or rebuild specific components.
|
|
</para>
|
|
|
|
<para>
|
|
The
|
|
<link linkend='ref-classes-sstate'><filename>sstate</filename></link>
|
|
class is a relatively generic implementation of how to "capture"
|
|
a snapshot of a given task.
|
|
The idea is that the build process does not care about the source of a task's output.
|
|
Output could be freshly built or it could be downloaded and unpacked from
|
|
somewhere - the build process does not need to worry about its origin.
|
|
</para>
|
|
|
|
<para>
|
|
There are two types of output, one is just about creating a directory
|
|
in <link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>.
|
|
A good example is the output of either
|
|
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
|
|
or
|
|
<link linkend='ref-tasks-package'><filename>do_package</filename></link>.
|
|
The other type of output occurs when a set of data is merged into a shared directory
|
|
tree such as the sysroot.
|
|
</para>
|
|
|
|
<para>
|
|
The Yocto Project team has tried to keep the details of the
|
|
implementation hidden in <filename>sstate</filename> class.
|
|
From a user's perspective, adding shared state wrapping to a task
|
|
is as simple as this
|
|
<link linkend='ref-tasks-deploy'><filename>do_deploy</filename></link>
|
|
example taken from the
|
|
<link linkend='ref-classes-deploy'><filename>deploy</filename></link>
|
|
class:
|
|
<literallayout class='monospaced'>
|
|
DEPLOYDIR = "${WORKDIR}/deploy-${PN}"
|
|
SSTATETASKS += "do_deploy"
|
|
do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"
|
|
do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"
|
|
|
|
python do_deploy_setscene () {
|
|
sstate_setscene(d)
|
|
}
|
|
addtask do_deploy_setscene
|
|
do_deploy[dirs] = "${DEPLOYDIR} ${B}"
|
|
</literallayout>
|
|
The following list explains the previous example:
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
Adding "do_deploy" to <filename>SSTATETASKS</filename>
|
|
adds some required sstate-related processing, which is
|
|
implemented in the
|
|
<link linkend='ref-classes-sstate'><filename>sstate</filename></link>
|
|
class, to before and after the
|
|
<link linkend='ref-tasks-deploy'><filename>do_deploy</filename></link>
|
|
task.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
The
|
|
<filename>do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"</filename>
|
|
declares that <filename>do_deploy</filename> places its
|
|
output in <filename>${DEPLOYDIR}</filename> when run
|
|
normally (i.e. when not using the sstate cache).
|
|
This output becomes the input to the shared state cache.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
The
|
|
<filename>do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"</filename>
|
|
line causes the contents of the shared state cache to be
|
|
copied to <filename>${DEPLOY_DIR_IMAGE}</filename>.
|
|
<note>
|
|
If <filename>do_deploy</filename> is not already in
|
|
the shared state cache or if its input checksum
|
|
(signature) has changed from when the output was
|
|
cached, the task will be run to populate the shared
|
|
state cache, after which the contents of the shared
|
|
state cache is copied to
|
|
<filename>${DEPLOY_DIR_IMAGE}</filename>.
|
|
If <filename>do_deploy</filename> is in the shared
|
|
state cache and its signature indicates that the
|
|
cached output is still valid (i.e. if no
|
|
relevant task inputs have changed), then the contents
|
|
of the shared state cache will be copied directly to
|
|
<filename>${DEPLOY_DIR_IMAGE}</filename> by the
|
|
<filename>do_deploy_setscene</filename> task instead,
|
|
skipping the <filename>do_deploy</filename> task.
|
|
</note>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
The following task definition is glue logic needed to make
|
|
the previous settings effective:
|
|
<literallayout class='monospaced'>
|
|
python do_deploy_setscene () {
|
|
sstate_setscene(d)
|
|
}
|
|
addtask do_deploy_setscene
|
|
</literallayout>
|
|
<filename>sstate_setscene()</filename> takes the flags
|
|
above as input and accelerates the
|
|
<filename>do_deploy</filename> task through the
|
|
shared state cache if possible.
|
|
If the task was accelerated,
|
|
<filename>sstate_setscene()</filename> returns True.
|
|
Otherwise, it returns False, and the normal
|
|
<filename>do_deploy</filename> task runs.
|
|
For more information, see the
|
|
"<ulink url='&YOCTO_DOCS_BB_URL;#setscene'>setscene</ulink>"
|
|
section in the BitBake User Manual.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
The <filename>do_deploy[dirs] = "${DEPLOYDIR} ${B}"</filename>
|
|
line creates <filename>${DEPLOYDIR}</filename> and
|
|
<filename>${B}</filename> before the
|
|
<filename>do_deploy</filename> task runs, and also sets
|
|
the current working directory of
|
|
<filename>do_deploy</filename> to
|
|
<filename>${B}</filename>.
|
|
For more information, see the
|
|
"<ulink url='&YOCTO_DOCS_BB_URL;#variable-flags'>Variable Flags</ulink>"
|
|
section in the BitBake User Manual.
|
|
<note>
|
|
In cases where
|
|
<filename>sstate-inputdirs</filename> and
|
|
<filename>sstate-outputdirs</filename> would be the
|
|
same, you can use
|
|
<filename>sstate-plaindirs</filename>.
|
|
For example, to preserve the
|
|
<filename>${PKGD}</filename> and
|
|
<filename>${PKGDEST}</filename> output from the
|
|
<link linkend='ref-tasks-package'><filename>do_package</filename></link>
|
|
task, use the following:
|
|
<literallayout class='monospaced'>
|
|
do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}"
|
|
</literallayout>
|
|
</note>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>sstate-inputdirs</filename> and
|
|
<filename>sstate-outputdirs</filename> can also be used
|
|
with multiple directories.
|
|
For example, the following declares
|
|
<filename>PKGDESTWORK</filename> and
|
|
<filename>SHLIBWORK</filename> as shared state
|
|
input directories, which populates the shared state
|
|
cache, and <filename>PKGDATA_DIR</filename> and
|
|
<filename>SHLIBSDIR</filename> as the corresponding
|
|
shared state output directories:
|
|
<literallayout class='monospaced'>
|
|
do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}"
|
|
do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}"
|
|
</literallayout>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
These methods also include the ability to take a lockfile
|
|
when manipulating shared state directory structures,
|
|
for cases where file additions or removals are sensitive:
|
|
<literallayout class='monospaced'>
|
|
do_package[sstate-lockfile] = "${PACKAGELOCK}"
|
|
</literallayout>
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<!--
|
|
<para>
|
|
In this example, we add some extra flags to the task, a name field ("deploy"), an
|
|
input directory where the task sends data, and the output
|
|
directory where the data from the task should eventually be copied.
|
|
We also add a <filename>_setscene</filename> variant of the task and add the task
|
|
name to the <filename>SSTATETASKS</filename> list.
|
|
</para>
|
|
|
|
<para>
|
|
If you have a directory whose contents you need to preserve, you can do this with
|
|
a line like the following:
|
|
<literallayout class='monospaced'>
|
|
do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}"
|
|
</literallayout>
|
|
This method, as well as the following example, also works for multiple directories.
|
|
<literallayout class='monospaced'>
|
|
do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}"
|
|
do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}"
|
|
do_package[sstate-lockfile] = "${PACKAGELOCK}"
|
|
</literallayout>
|
|
These methods also include the ability to take a lockfile when manipulating
|
|
shared state directory structures since some cases are sensitive to file
|
|
additions or removals.
|
|
</para>
|
|
-->
|
|
|
|
<para>
|
|
Behind the scenes, the shared state code works by looking in
|
|
<link linkend='var-SSTATE_DIR'><filename>SSTATE_DIR</filename></link> and
|
|
<link linkend='var-SSTATE_MIRRORS'><filename>SSTATE_MIRRORS</filename></link>
|
|
for shared state files.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
SSTATE_MIRRORS ?= "\
|
|
file://.* http://someserver.tld/share/sstate/PATH;downloadfilename=PATH \n \
|
|
file://.* file:///some/local/dir/sstate/PATH"
|
|
</literallayout>
|
|
<note>
|
|
The shared state directory (<filename>SSTATE_DIR</filename>) is
|
|
organized into two-character subdirectories, where the subdirectory
|
|
names are based on the first two characters of the hash.
|
|
If the shared state directory structure for a mirror has the
|
|
same structure as <filename>SSTATE_DIR</filename>, you must
|
|
specify "PATH" as part of the URI to enable the build system
|
|
to map to the appropriate subdirectory.
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
The shared state package validity can be detected just by looking at the
|
|
filename since the filename contains the task checksum (or signature) as
|
|
described earlier in this section.
|
|
If a valid shared state package is found, the build process downloads it
|
|
and uses it to accelerate the task.
|
|
</para>
|
|
|
|
<para>
|
|
The build processes use the <filename>*_setscene</filename> tasks
|
|
for the task acceleration phase.
|
|
BitBake goes through this phase before the main execution code and tries
|
|
to accelerate any tasks for which it can find shared state packages.
|
|
If a shared state package for a task is available, the shared state
|
|
package is used.
|
|
This means the task and any tasks on which it is dependent are not
|
|
executed.
|
|
</para>
|
|
|
|
<para>
|
|
As a real world example, the aim is when building an IPK-based image,
|
|
only the
|
|
<link linkend='ref-tasks-package_write_ipk'><filename>do_package_write_ipk</filename></link>
|
|
tasks would have their
|
|
shared state packages fetched and extracted.
|
|
Since the sysroot is not used, it would never get extracted.
|
|
This is another reason why a task-based approach is preferred over a
|
|
recipe-based approach, which would have to install the output from every task.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='tips-and-tricks'>
|
|
<title>Tips and Tricks</title>
|
|
|
|
<para>
|
|
The code in the build system that supports incremental builds is not
|
|
simple code.
|
|
This section presents some tips and tricks that help you work around
|
|
issues related to shared state code.
|
|
</para>
|
|
|
|
<section id='debugging'>
|
|
<title>Debugging</title>
|
|
|
|
<para>
|
|
Seeing what metadata went into creating the input signature
|
|
of a shared state (sstate) task can be a useful debugging aid.
|
|
This information is available in signature information
|
|
(<filename>siginfo</filename>) files in
|
|
<link linkend='var-SSTATE_DIR'><filename>SSTATE_DIR</filename></link>.
|
|
For information on how to view and interpret information in
|
|
<filename>siginfo</filename> files, see the
|
|
"<link linkend='usingpoky-viewing-task-variable-dependencies'>Viewing Task Variable Dependencies</link>"
|
|
section.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='invalidating-shared-state'>
|
|
<title>Invalidating Shared State</title>
|
|
|
|
<para>
|
|
The OpenEmbedded build system uses checksums and shared state
|
|
cache to avoid unnecessarily rebuilding tasks.
|
|
Collectively, this scheme is known as "shared state code."
|
|
</para>
|
|
|
|
<para>
|
|
As with all schemes, this one has some drawbacks.
|
|
It is possible that you could make implicit changes to your
|
|
code that the checksum calculations do not take into
|
|
account.
|
|
These implicit changes affect a task's output but do not trigger
|
|
the shared state code into rebuilding a recipe.
|
|
Consider an example during which a tool changes its output.
|
|
Assume that the output of <filename>rpmdeps</filename> changes.
|
|
The result of the change should be that all the
|
|
<filename>package</filename> and
|
|
<filename>package_write_rpm</filename> shared state cache
|
|
items become invalid.
|
|
However, because the change to the output is
|
|
external to the code and therefore implicit,
|
|
the associated shared state cache items do not become
|
|
invalidated.
|
|
In this case, the build process uses the cached items rather
|
|
than running the task again.
|
|
Obviously, these types of implicit changes can cause problems.
|
|
</para>
|
|
|
|
<para>
|
|
To avoid these problems during the build, you need to
|
|
understand the effects of any changes you make.
|
|
Realize that changes you make directly to a function
|
|
are automatically factored into the checksum calculation.
|
|
Thus, these explicit changes invalidate the associated area of
|
|
shared state cache.
|
|
However, you need to be aware of any implicit changes that
|
|
are not obvious changes to the code and could affect the output
|
|
of a given task.
|
|
</para>
|
|
|
|
<para>
|
|
When you identify an implicit change, you can easily take steps
|
|
to invalidate the cache and force the tasks to run.
|
|
The steps you can take are as simple as changing a function's
|
|
comments in the source code.
|
|
For example, to invalidate package shared state files, change
|
|
the comment statements of
|
|
<link linkend='ref-tasks-package'><filename>do_package</filename></link>
|
|
or the comments of one of the functions it calls.
|
|
Even though the change is purely cosmetic, it causes the
|
|
checksum to be recalculated and forces the OpenEmbedded build
|
|
system to run the task again.
|
|
</para>
|
|
|
|
<note>
|
|
For an example of a commit that makes a cosmetic change to
|
|
invalidate shared state, see this
|
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/commit/meta/classes/package.bbclass?id=737f8bbb4f27b4837047cb9b4fbfe01dfde36d54'>commit</ulink>.
|
|
</note>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='automatically-added-runtime-dependencies'>
|
|
<title>Automatically Added Runtime Dependencies</title>
|
|
|
|
<para>
|
|
The OpenEmbedded build system automatically adds common types of
|
|
runtime dependencies between packages, which means that you do not
|
|
need to explicitly declare the packages using
|
|
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>.
|
|
Three automatic mechanisms exist (<filename>shlibdeps</filename>,
|
|
<filename>pcdeps</filename>, and <filename>depchains</filename>) that
|
|
handle shared libraries, package configuration (pkg-config) modules,
|
|
and <filename>-dev</filename> and <filename>-dbg</filename> packages,
|
|
respectively.
|
|
For other types of runtime dependencies, you must manually declare
|
|
the dependencies.
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
<filename>shlibdeps</filename>:
|
|
During the
|
|
<link linkend='ref-tasks-package'><filename>do_package</filename></link>
|
|
task of each recipe, all shared libraries installed by the
|
|
recipe are located.
|
|
For each shared library, the package that contains the shared
|
|
library is registered as providing the shared library.
|
|
More specifically, the package is registered as providing the
|
|
<ulink url='https://en.wikipedia.org/wiki/Soname'>soname</ulink>
|
|
of the library.
|
|
The resulting shared-library-to-package mapping
|
|
is saved globally in
|
|
<link linkend='var-PKGDATA_DIR'><filename>PKGDATA_DIR</filename></link>
|
|
by the
|
|
<link linkend='ref-tasks-packagedata'><filename>do_packagedata</filename></link>
|
|
task.</para>
|
|
|
|
<para>Simultaneously, all executables and shared libraries
|
|
installed by the recipe are inspected to see what shared
|
|
libraries they link against.
|
|
For each shared library dependency that is found,
|
|
<filename>PKGDATA_DIR</filename> is queried to
|
|
see if some package (likely from a different recipe) contains
|
|
the shared library.
|
|
If such a package is found, a runtime dependency is added from
|
|
the package that depends on the shared library to the package
|
|
that contains the library.</para>
|
|
|
|
<para>The automatically added runtime dependency also includes
|
|
a version restriction.
|
|
This version restriction specifies that at least the current
|
|
version of the package that provides the shared library must be
|
|
used, as if
|
|
"<replaceable>package</replaceable> (>= <replaceable>version</replaceable>)"
|
|
had been added to
|
|
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>.
|
|
This forces an upgrade of the package containing the shared
|
|
library when installing the package that depends on the
|
|
library, if needed.</para>
|
|
|
|
<para>If you want to avoid a package being registered as
|
|
providing a particular shared library (e.g. because the library
|
|
is for internal use only), then add the library to
|
|
<link linkend='var-PRIVATE_LIBS'><filename>PRIVATE_LIBS</filename></link>
|
|
inside the package's recipe.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>pcdeps</filename>:
|
|
During the
|
|
<link linkend='ref-tasks-package'><filename>do_package</filename></link>
|
|
task of each recipe, all pkg-config modules
|
|
(<filename>*.pc</filename> files) installed by the recipe are
|
|
located.
|
|
For each module, the package that contains the module is
|
|
registered as providing the module.
|
|
The resulting module-to-package mapping is saved globally in
|
|
<link linkend='var-PKGDATA_DIR'><filename>PKGDATA_DIR</filename></link>
|
|
by the
|
|
<link linkend='ref-tasks-packagedata'><filename>do_packagedata</filename></link>
|
|
task.</para>
|
|
|
|
<para>Simultaneously, all pkg-config modules installed by the
|
|
recipe are inspected to see what other pkg-config modules they
|
|
depend on.
|
|
A module is seen as depending on another module if it contains
|
|
a "Requires:" line that specifies the other module.
|
|
For each module dependency,
|
|
<filename>PKGDATA_DIR</filename> is queried to see if some
|
|
package contains the module.
|
|
If such a package is found, a runtime dependency is added from
|
|
the package that depends on the module to the package that
|
|
contains the module.
|
|
<note>
|
|
The <filename>pcdeps</filename> mechanism most often infers
|
|
dependencies between <filename>-dev</filename> packages.
|
|
</note>
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<filename>depchains</filename>:
|
|
If a package <filename>foo</filename> depends on a package
|
|
<filename>bar</filename>, then <filename>foo-dev</filename>
|
|
and <filename>foo-dbg</filename> are also made to depend on
|
|
<filename>bar-dev</filename> and <filename>bar-dbg</filename>,
|
|
respectively.
|
|
Taking the <filename>-dev</filename> packages as an example,
|
|
the <filename>bar-dev</filename> package might provide
|
|
headers and shared library symlinks needed by
|
|
<filename>foo-dev</filename>, which shows the need
|
|
for a dependency between the packages.</para>
|
|
|
|
<para>The dependencies added by <filename>depchains</filename>
|
|
are in the form of
|
|
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>.
|
|
<note>
|
|
By default, <filename>foo-dev</filename> also has an
|
|
<filename>RDEPENDS</filename>-style dependency on
|
|
<filename>foo</filename>, because the default value of
|
|
<filename>RDEPENDS_${PN}-dev</filename> (set in
|
|
<filename>bitbake.conf</filename>) includes
|
|
"${PN}".
|
|
</note></para>
|
|
|
|
<para>To ensure that the dependency chain is never broken,
|
|
<filename>-dev</filename> and <filename>-dbg</filename>
|
|
packages are always generated by default, even if the packages
|
|
turn out to be empty.
|
|
See the
|
|
<link linkend='var-ALLOW_EMPTY'><filename>ALLOW_EMPTY</filename></link>
|
|
variable for more information.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
The <filename>do_package</filename> task depends on the
|
|
<link linkend='ref-tasks-packagedata'><filename>do_packagedata</filename></link>
|
|
task of each recipe in
|
|
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
|
|
through use of a
|
|
<filename>[</filename><ulink url='&YOCTO_DOCS_BB_URL;#variable-flags'><filename>deptask</filename></ulink><filename>]</filename>
|
|
declaration, which guarantees that the required
|
|
shared-library/module-to-package mapping information will be available
|
|
when needed as long as <filename>DEPENDS</filename> has been
|
|
correctly set.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='fakeroot-and-pseudo'>
|
|
<title>Fakeroot and Pseudo</title>
|
|
|
|
<para>
|
|
Some tasks are easier to implement when allowed to perform certain
|
|
operations that are normally reserved for the root user.
|
|
For example, the
|
|
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
|
|
task benefits from being able to set the UID and GID of installed files
|
|
to arbitrary values.
|
|
</para>
|
|
|
|
<para>
|
|
One approach to allowing tasks to perform root-only operations
|
|
would be to require BitBake to run as root.
|
|
However, this method is cumbersome and has security issues.
|
|
The approach that is actually used is to run tasks that benefit from
|
|
root privileges in a "fake" root environment.
|
|
Within this environment, the task and its child processes believe that
|
|
they are running as the root user, and see an internally consistent
|
|
view of the filesystem.
|
|
As long as generating the final output (e.g. a package or an image)
|
|
does not require root privileges, the fact that some earlier steps ran
|
|
in a fake root environment does not cause problems.
|
|
</para>
|
|
|
|
<para>
|
|
The capability to run tasks in a fake root environment is known as
|
|
"fakeroot", which is derived from the BitBake keyword/variable
|
|
flag that requests a fake root environment for a task.
|
|
In current versions of the OpenEmbedded build system,
|
|
the program that implements fakeroot is known as Pseudo.
|
|
</para>
|
|
|
|
<para>
|
|
Pseudo overrides system calls through the
|
|
<filename>LD_PRELOAD</filename> mechanism to give the
|
|
illusion of running as root.
|
|
To keep track of "fake" file ownership and permissions resulting from
|
|
operations that require root permissions, an sqlite3
|
|
database is used.
|
|
This database is stored in
|
|
<filename>${</filename><link linkend='var-WORKDIR'><filename>WORKDIR</filename></link><filename>}/pseudo/files.db</filename>
|
|
for individual recipes.
|
|
Storing the database in a file as opposed to in memory
|
|
gives persistence between tasks, and even between builds.
|
|
<note><title>Caution</title>
|
|
If you add your own task that manipulates the same files or
|
|
directories as a fakeroot task, then that task should also run
|
|
under fakeroot.
|
|
Otherwise, the task will not be able to run root-only operations,
|
|
and will not see the fake file ownership and permissions set by the
|
|
other task.
|
|
You should also add a dependency on
|
|
<filename>virtual/fakeroot-native:do_populate_sysroot</filename>,
|
|
giving the following:
|
|
<literallayout class='monospaced'>
|
|
fakeroot do_mytask () {
|
|
...
|
|
}
|
|
do_mytask[depends] += "virtual/fakeroot-native:do_populate_sysroot"
|
|
</literallayout>
|
|
</note>
|
|
For more information, see the
|
|
<ulink url='&YOCTO_DOCS_BB_URL;#var-FAKEROOT'><filename>FAKEROOT*</filename></ulink>
|
|
variables in the BitBake User Manual.
|
|
You can also reference this
|
|
<ulink url='http://www.ibm.com/developerworks/opensource/library/os-aapseudo1/index.html'>Pseudo</ulink>
|
|
article.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='x32'>
|
|
<title>x32</title>
|
|
|
|
<para>
|
|
x32 is a processor-specific Application Binary Interface (psABI) for x86_64.
|
|
An ABI defines the calling conventions between functions in a processing environment.
|
|
The interface determines what registers are used and what the sizes are for various C data types.
|
|
</para>
|
|
|
|
<para>
|
|
Some processing environments prefer using 32-bit applications even when running
|
|
on Intel 64-bit platforms.
|
|
Consider the i386 psABI, which is a very old 32-bit ABI for Intel 64-bit platforms.
|
|
The i386 psABI does not provide efficient use and access of the Intel 64-bit processor resources,
|
|
leaving the system underutilized.
|
|
Now consider the x86_64 psABI.
|
|
This ABI is newer and uses 64-bits for data sizes and program pointers.
|
|
The extra bits increase the footprint size of the programs, libraries,
|
|
and also increases the memory and file system size requirements.
|
|
Executing under the x32 psABI enables user programs to utilize CPU and system resources
|
|
more efficiently while keeping the memory footprint of the applications low.
|
|
Extra bits are used for registers but not for addressing mechanisms.
|
|
</para>
|
|
|
|
<section id='support'>
|
|
<title>Support</title>
|
|
|
|
<para>
|
|
This Yocto Project release supports the final specifications of x32
|
|
psABI.
|
|
Support for x32 psABI exists as follows:
|
|
<itemizedlist>
|
|
<listitem><para>You can create packages and images in x32 psABI format on x86_64 architecture targets.
|
|
</para></listitem>
|
|
<listitem><para>You can successfully build many recipes with the x32 toolchain.</para></listitem>
|
|
<listitem><para>You can create and boot <filename>core-image-minimal</filename> and
|
|
<filename>core-image-sato</filename> images.</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='completing-x32'>
|
|
<title>Completing x32</title>
|
|
|
|
<para>
|
|
Future Plans for the x32 psABI in the Yocto Project include the following:
|
|
<itemizedlist>
|
|
<listitem><para>Enhance and fix the few remaining recipes so they
|
|
work with and support x32 toolchains.</para></listitem>
|
|
<listitem><para>Enhance RPM Package Manager (RPM) support for x32 binaries.</para></listitem>
|
|
<listitem><para>Support larger images.</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='using-x32-right-now'>
|
|
<title>Using x32 Right Now</title>
|
|
|
|
<para>
|
|
Follow these steps to use the x32 spABI:
|
|
<itemizedlist>
|
|
<listitem><para>Enable the x32 psABI tuning file for <filename>x86_64</filename>
|
|
machines by editing the <filename>conf/local.conf</filename> like this:
|
|
<literallayout class='monospaced'>
|
|
MACHINE = "qemux86-64"
|
|
DEFAULTTUNE = "x86-64-x32"
|
|
baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) \
|
|
or 'INVALID'), True) or 'lib'}"
|
|
#MACHINE = "genericx86"
|
|
#DEFAULTTUNE = "core2-64-x32"
|
|
</literallayout></para></listitem>
|
|
<listitem><para>As usual, use BitBake to build an image that supports the x32 psABI.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake core-image-sato
|
|
</literallayout></para></listitem>
|
|
<listitem><para>As usual, run your image using QEMU:
|
|
<literallayout class='monospaced'>
|
|
$ runqemu qemux86-64 core-image-sato
|
|
</literallayout></para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="wayland">
|
|
<title>Wayland</title>
|
|
|
|
<para>
|
|
<ulink url='http://en.wikipedia.org/wiki/Wayland_(display_server_protocol)'>Wayland</ulink>
|
|
is a computer display server protocol that
|
|
provides a method for compositing window managers to communicate
|
|
directly with applications and video hardware and expects them to
|
|
communicate with input hardware using other libraries.
|
|
Using Wayland with supporting targets can result in better control
|
|
over graphics frame rendering than an application might otherwise
|
|
achieve.
|
|
</para>
|
|
|
|
<para>
|
|
The Yocto Project provides the Wayland protocol libraries and the
|
|
reference
|
|
<ulink url='http://en.wikipedia.org/wiki/Wayland_(display_server_protocol)#Weston'>Weston</ulink>
|
|
compositor as part of its release.
|
|
This section describes what you need to do to implement Wayland and
|
|
use the compositor when building an image for a supporting target.
|
|
</para>
|
|
|
|
<section id="wayland-support">
|
|
<title>Support</title>
|
|
|
|
<para>
|
|
The Wayland protocol libraries and the reference Weston compositor
|
|
ship as integrated packages in the <filename>meta</filename> layer
|
|
of the
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
|
|
Specifically, you can find the recipes that build both Wayland
|
|
and Weston at <filename>meta/recipes-graphics/wayland</filename>.
|
|
</para>
|
|
|
|
<para>
|
|
You can build both the Wayland and Weston packages for use only
|
|
with targets that accept the
|
|
<ulink url='http://dri.freedesktop.org/wiki/'>Mesa 3D and Direct Rendering Infrastructure</ulink>,
|
|
which is also known as Mesa DRI.
|
|
This implies that you cannot build and use the packages if your
|
|
target uses, for example, the
|
|
<trademark class='registered'>Intel</trademark> Embedded Media and
|
|
Graphics Driver (<trademark class='registered'>Intel</trademark>
|
|
EMGD) that overrides Mesa DRI.
|
|
</para>
|
|
|
|
<note>
|
|
Due to lack of EGL support, Weston 1.0.3 will not run directly on
|
|
the emulated QEMU hardware.
|
|
However, this version of Weston will run under X emulation without
|
|
issues.
|
|
</note>
|
|
</section>
|
|
|
|
<section id="enabling-wayland-in-an-image">
|
|
<title>Enabling Wayland in an Image</title>
|
|
|
|
<para>
|
|
To enable Wayland, you need to enable it to be built and enable
|
|
it to be included in the image.
|
|
</para>
|
|
|
|
<section id="enable-building">
|
|
<title>Building</title>
|
|
|
|
<para>
|
|
To cause Mesa to build the <filename>wayland-egl</filename>
|
|
platform and Weston to build Wayland with Kernel Mode
|
|
Setting
|
|
(<ulink url='https://wiki.archlinux.org/index.php/Kernel_Mode_Setting'>KMS</ulink>)
|
|
support, include the "wayland" flag in the
|
|
<link linkend="var-DISTRO_FEATURES"><filename>DISTRO_FEATURES</filename></link>
|
|
statement in your <filename>local.conf</filename> file:
|
|
<literallayout class='monospaced'>
|
|
DISTRO_FEATURES_append = " wayland"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<note>
|
|
If X11 has been enabled elsewhere, Weston will build Wayland
|
|
with X11 support
|
|
</note>
|
|
</section>
|
|
|
|
<section id="enable-installation-in-an-image">
|
|
<title>Installing</title>
|
|
|
|
<para>
|
|
To install the Wayland feature into an image, you must
|
|
include the following
|
|
<link linkend='var-CORE_IMAGE_EXTRA_INSTALL'><filename>CORE_IMAGE_EXTRA_INSTALL</filename></link>
|
|
statement in your <filename>local.conf</filename> file:
|
|
<literallayout class='monospaced'>
|
|
CORE_IMAGE_EXTRA_INSTALL += "wayland weston"
|
|
</literallayout>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="running-weston">
|
|
<title>Running Weston</title>
|
|
|
|
<para>
|
|
To run Weston inside X11, enabling it as described earlier and
|
|
building a Sato image is sufficient.
|
|
If you are running your image under Sato, a Weston Launcher appears
|
|
in the "Utility" category.
|
|
</para>
|
|
|
|
<para>
|
|
Alternatively, you can run Weston through the command-line
|
|
interpretor (CLI), which is better suited for development work.
|
|
To run Weston under the CLI, you need to do the following after
|
|
your image is built:
|
|
<orderedlist>
|
|
<listitem><para>Run these commands to export
|
|
<filename>XDG_RUNTIME_DIR</filename>:
|
|
<literallayout class='monospaced'>
|
|
mkdir -p /tmp/$USER-weston
|
|
chmod 0700 /tmp/$USER-weston
|
|
export XDG_RUNTIME_DIR=/tmp/$USER-weston
|
|
</literallayout></para></listitem>
|
|
<listitem><para>Launch Weston in the shell:
|
|
<literallayout class='monospaced'>
|
|
weston
|
|
</literallayout></para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="licenses">
|
|
<title>Licenses</title>
|
|
|
|
<para>
|
|
This section describes the mechanism by which the OpenEmbedded build system
|
|
tracks changes to licensing text.
|
|
The section also describes how to enable commercially licensed recipes,
|
|
which by default are disabled.
|
|
</para>
|
|
|
|
<para>
|
|
For information that can help you maintain compliance with various open
|
|
source licensing during the lifecycle of the product, see the
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#maintaining-open-source-license-compliance-during-your-products-lifecycle'>Maintaining Open Source License Compliance During Your Project's Lifecycle</ulink>" section
|
|
in the Yocto Project Development Manual.
|
|
</para>
|
|
|
|
<section id="usingpoky-configuring-LIC_FILES_CHKSUM">
|
|
<title>Tracking License Changes</title>
|
|
|
|
<para>
|
|
The license of an upstream project might change in the future.
|
|
In order to prevent these changes going unnoticed, the
|
|
<filename><link linkend='var-LIC_FILES_CHKSUM'>LIC_FILES_CHKSUM</link></filename>
|
|
variable tracks changes to the license text. The checksums are validated at the end of the
|
|
configure step, and if the checksums do not match, the build will fail.
|
|
</para>
|
|
|
|
<section id="usingpoky-specifying-LIC_FILES_CHKSUM">
|
|
<title>Specifying the <filename>LIC_FILES_CHKSUM</filename> Variable</title>
|
|
|
|
<para>
|
|
The <filename>LIC_FILES_CHKSUM</filename>
|
|
variable contains checksums of the license text in the source
|
|
code for the recipe.
|
|
Following is an example of how to specify
|
|
<filename>LIC_FILES_CHKSUM</filename>:
|
|
<literallayout class='monospaced'>
|
|
LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \
|
|
file://licfile1.txt;beginline=5;endline=29;md5=yyyy \
|
|
file://licfile2.txt;endline=50;md5=zzzz \
|
|
..."
|
|
</literallayout>
|
|
<note><title>Notes</title>
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
When using "beginline" and "endline", realize that
|
|
line numbering begins with one and not zero.
|
|
Also, the included lines are inclusive (i.e. lines
|
|
five through and including 29 in the previous
|
|
example for <filename>licfile1.txt</filename>).
|
|
</para></listitem>
|
|
<listitem><para>
|
|
When a license check fails, the selected license
|
|
text is included as part of the QA message.
|
|
Using this output, you can determine the exact
|
|
start and finish for the needed license text.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
The build system uses the
|
|
<filename><link linkend='var-S'>S</link></filename> variable as
|
|
the default directory when searching files listed in
|
|
<filename>LIC_FILES_CHKSUM</filename>.
|
|
The previous example employs the default directory.
|
|
</para>
|
|
|
|
<para>
|
|
Consider this next example:
|
|
<literallayout class='monospaced'>
|
|
LIC_FILES_CHKSUM = "file://src/ls.c;beginline=5;endline=16;\
|
|
md5=bb14ed3c4cda583abc85401304b5cd4e"
|
|
LIC_FILES_CHKSUM = "file://${WORKDIR}/license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
The first line locates a file in
|
|
<filename>${S}/src/ls.c</filename> and isolates lines five
|
|
through 16 as license text.
|
|
The second line refers to a file in
|
|
<filename><link linkend='var-WORKDIR'>WORKDIR</link></filename>.
|
|
</para>
|
|
<para>
|
|
Note that <filename>LIC_FILES_CHKSUM</filename> variable is
|
|
mandatory for all recipes, unless the
|
|
<filename>LICENSE</filename> variable is set to "CLOSED".
|
|
</para>
|
|
</section>
|
|
|
|
<section id="usingpoky-LIC_FILES_CHKSUM-explanation-of-syntax">
|
|
<title>Explanation of Syntax</title>
|
|
<para>
|
|
As mentioned in the previous section, the
|
|
<filename>LIC_FILES_CHKSUM</filename> variable lists all the
|
|
important files that contain the license text for the source code.
|
|
It is possible to specify a checksum for an entire file, or a specific section of a
|
|
file (specified by beginning and ending line numbers with the "beginline" and "endline"
|
|
parameters, respectively).
|
|
The latter is useful for source files with a license notice header,
|
|
README documents, and so forth.
|
|
If you do not use the "beginline" parameter, then it is assumed that the text begins on the
|
|
first line of the file.
|
|
Similarly, if you do not use the "endline" parameter, it is assumed that the license text
|
|
ends with the last line of the file.
|
|
</para>
|
|
|
|
<para>
|
|
The "md5" parameter stores the md5 checksum of the license text.
|
|
If the license text changes in any way as compared to this parameter
|
|
then a mismatch occurs.
|
|
This mismatch triggers a build failure and notifies the developer.
|
|
Notification allows the developer to review and address the license text changes.
|
|
Also note that if a mismatch occurs during the build, the correct md5
|
|
checksum is placed in the build log and can be easily copied to the recipe.
|
|
</para>
|
|
|
|
<para>
|
|
There is no limit to how many files you can specify using the
|
|
<filename>LIC_FILES_CHKSUM</filename> variable.
|
|
Generally, however, every project requires a few specifications for license tracking.
|
|
Many projects have a "COPYING" file that stores the license information for all the source
|
|
code files.
|
|
This practice allows you to just track the "COPYING" file as long as it is kept up to date.
|
|
</para>
|
|
|
|
<tip>
|
|
If you specify an empty or invalid "md5" parameter, BitBake returns an md5 mis-match
|
|
error and displays the correct "md5" parameter value during the build.
|
|
The correct parameter is also captured in the build log.
|
|
</tip>
|
|
|
|
<tip>
|
|
If the whole file contains only license text, you do not need to use the "beginline" and
|
|
"endline" parameters.
|
|
</tip>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="enabling-commercially-licensed-recipes">
|
|
<title>Enabling Commercially Licensed Recipes</title>
|
|
|
|
<para>
|
|
By default, the OpenEmbedded build system disables
|
|
components that have commercial or other special licensing
|
|
requirements.
|
|
Such requirements are defined on a
|
|
recipe-by-recipe basis through the
|
|
<link linkend='var-LICENSE_FLAGS'><filename>LICENSE_FLAGS</filename></link>
|
|
variable definition in the affected recipe.
|
|
For instance, the
|
|
<filename>poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly</filename>
|
|
recipe contains the following statement:
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS = "commercial"
|
|
</literallayout>
|
|
Here is a slightly more complicated example that contains both an
|
|
explicit recipe name and version (after variable expansion):
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS = "license_${PN}_${PV}"
|
|
</literallayout>
|
|
In order for a component restricted by a <filename>LICENSE_FLAGS</filename>
|
|
definition to be enabled and included in an image, it
|
|
needs to have a matching entry in the global
|
|
<link linkend='var-LICENSE_FLAGS_WHITELIST'><filename>LICENSE_FLAGS_WHITELIST</filename></link>
|
|
variable, which is a variable
|
|
typically defined in your <filename>local.conf</filename> file.
|
|
For example, to enable
|
|
the <filename>poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly</filename>
|
|
package, you could add either the string
|
|
"commercial_gst-plugins-ugly" or the more general string
|
|
"commercial" to <filename>LICENSE_FLAGS_WHITELIST</filename>.
|
|
See the
|
|
"<link linkend='license-flag-matching'>License Flag Matching</link>" section
|
|
for a full explanation of how <filename>LICENSE_FLAGS</filename> matching works.
|
|
Here is the example:
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly"
|
|
</literallayout>
|
|
Likewise, to additionally enable the package built from the recipe containing
|
|
<filename>LICENSE_FLAGS = "license_${PN}_${PV}"</filename>, and assuming
|
|
that the actual recipe name was <filename>emgd_1.10.bb</filename>,
|
|
the following string would enable that package as well as
|
|
the original <filename>gst-plugins-ugly</filename> package:
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10"
|
|
</literallayout>
|
|
As a convenience, you do not need to specify the complete license string
|
|
in the whitelist for every package.
|
|
You can use an abbreviated form, which consists
|
|
of just the first portion or portions of the license string before
|
|
the initial underscore character or characters.
|
|
A partial string will match
|
|
any license that contains the given string as the first
|
|
portion of its license.
|
|
For example, the following
|
|
whitelist string will also match both of the packages
|
|
previously mentioned as well as any other packages that have
|
|
licenses starting with "commercial" or "license".
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS_WHITELIST = "commercial license"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<section id="license-flag-matching">
|
|
<title>License Flag Matching</title>
|
|
|
|
<para>
|
|
License flag matching allows you to control what recipes the
|
|
OpenEmbedded build system includes in the build.
|
|
Fundamentally, the build system attempts to match
|
|
<link linkend='var-LICENSE_FLAGS'><filename>LICENSE_FLAGS</filename></link>
|
|
strings found in recipes against
|
|
<link linkend='var-LICENSE_FLAGS_WHITELIST'><filename>LICENSE_FLAGS_WHITELIST</filename></link>
|
|
strings found in the whitelist.
|
|
A match causes the build system to include a recipe in the
|
|
build, while failure to find a match causes the build system to
|
|
exclude a recipe.
|
|
</para>
|
|
|
|
<para>
|
|
In general, license flag matching is simple.
|
|
However, understanding some concepts will help you
|
|
correctly and effectively use matching.
|
|
</para>
|
|
|
|
<para>
|
|
Before a flag
|
|
defined by a particular recipe is tested against the
|
|
contents of the whitelist, the expanded string
|
|
<filename>_${PN}</filename> is appended to the flag.
|
|
This expansion makes each <filename>LICENSE_FLAGS</filename>
|
|
value recipe-specific.
|
|
After expansion, the string is then matched against the
|
|
whitelist.
|
|
Thus, specifying
|
|
<filename>LICENSE_FLAGS = "commercial"</filename>
|
|
in recipe "foo", for example, results in the string
|
|
<filename>"commercial_foo"</filename>.
|
|
And, to create a match, that string must appear in the
|
|
whitelist.
|
|
</para>
|
|
|
|
<para>
|
|
Judicious use of the <filename>LICENSE_FLAGS</filename>
|
|
strings and the contents of the
|
|
<filename>LICENSE_FLAGS_WHITELIST</filename> variable
|
|
allows you a lot of flexibility for including or excluding
|
|
recipes based on licensing.
|
|
For example, you can broaden the matching capabilities by
|
|
using license flags string subsets in the whitelist.
|
|
<note>When using a string subset, be sure to use the part of
|
|
the expanded string that precedes the appended underscore
|
|
character (e.g. <filename>usethispart_1.3</filename>,
|
|
<filename>usethispart_1.4</filename>, and so forth).
|
|
</note>
|
|
For example, simply specifying the string "commercial" in
|
|
the whitelist matches any expanded
|
|
<filename>LICENSE_FLAGS</filename> definition that starts with
|
|
the string "commercial" such as "commercial_foo" and
|
|
"commercial_bar", which are the strings the build system
|
|
automatically generates for hypothetical recipes named
|
|
"foo" and "bar" assuming those recipes simply specify the
|
|
following:
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS = "commercial"
|
|
</literallayout>
|
|
Thus, you can choose to exhaustively
|
|
enumerate each license flag in the whitelist and
|
|
allow only specific recipes into the image, or
|
|
you can use a string subset that causes a broader range of
|
|
matches to allow a range of recipes into the image.
|
|
</para>
|
|
|
|
<para>
|
|
This scheme works even if the
|
|
<filename>LICENSE_FLAGS</filename> string already
|
|
has <filename>_${PN}</filename> appended.
|
|
For example, the build system turns the license flag
|
|
"commercial_1.2_foo" into "commercial_1.2_foo_foo" and would
|
|
match both the general "commercial" and the specific
|
|
"commercial_1.2_foo" strings found in the whitelist, as
|
|
expected.
|
|
</para>
|
|
|
|
<para>
|
|
Here are some other scenarios:
|
|
<itemizedlist>
|
|
<listitem><para>You can specify a versioned string in the
|
|
recipe such as "commercial_foo_1.2" in a "foo" recipe.
|
|
The build system expands this string to
|
|
"commercial_foo_1.2_foo".
|
|
Combine this license flag with a whitelist that has
|
|
the string "commercial" and you match the flag along
|
|
with any other flag that starts with the string
|
|
"commercial".</para></listitem>
|
|
<listitem><para>Under the same circumstances, you can
|
|
use "commercial_foo" in the whitelist and the
|
|
build system not only matches "commercial_foo_1.2" but
|
|
also matches any license flag with the string
|
|
"commercial_foo", regardless of the version.
|
|
</para></listitem>
|
|
<listitem><para>You can be very specific and use both the
|
|
package and version parts in the whitelist (e.g.
|
|
"commercial_foo_1.2") to specifically match a
|
|
versioned recipe.</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id="other-variables-related-to-commercial-licenses">
|
|
<title>Other Variables Related to Commercial Licenses</title>
|
|
|
|
<para>
|
|
Other helpful variables related to commercial
|
|
license handling exist and are defined in the
|
|
<filename>poky/meta/conf/distro/include/default-distrovars.inc</filename> file:
|
|
<literallayout class='monospaced'>
|
|
COMMERCIAL_AUDIO_PLUGINS ?= ""
|
|
COMMERCIAL_VIDEO_PLUGINS ?= ""
|
|
</literallayout>
|
|
If you want to enable these components, you can do so by making sure you have
|
|
statements similar to the following
|
|
in your <filename>local.conf</filename> configuration file:
|
|
<literallayout class='monospaced'>
|
|
COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \
|
|
gst-plugins-ugly-mpegaudioparse"
|
|
COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \
|
|
gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse"
|
|
LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial_qmmp"
|
|
</literallayout>
|
|
Of course, you could also create a matching whitelist
|
|
for those components using the more general "commercial"
|
|
in the whitelist, but that would also enable all the
|
|
other packages with
|
|
<link linkend='var-LICENSE_FLAGS'><filename>LICENSE_FLAGS</filename></link>
|
|
containing "commercial", which you may or may not want:
|
|
<literallayout class='monospaced'>
|
|
LICENSE_FLAGS_WHITELIST = "commercial"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Specifying audio and video plug-ins as part of the
|
|
<filename>COMMERCIAL_AUDIO_PLUGINS</filename> and
|
|
<filename>COMMERCIAL_VIDEO_PLUGINS</filename> statements
|
|
(along with the enabling
|
|
<filename>LICENSE_FLAGS_WHITELIST</filename>) includes the
|
|
plug-ins or components into built images, thus adding
|
|
support for media formats or components.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
</chapter>
|
|
<!--
|
|
vim: expandtab tw=80 ts=4
|
|
-->
|