483 lines
27 KiB
XML
483 lines
27 KiB
XML
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<!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='ref-features'>
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<title>Features</title>
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<para>
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This chapter provides a reference of shipped machine and distro features
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you can include as part of your image, a reference on image features you can
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select, and a reference on feature backfilling.
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</para>
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<para>
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Features provide a mechanism for working out which packages
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should be included in the generated images.
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Distributions can select which features they want to support through the
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<filename><link linkend='var-DISTRO_FEATURES'>DISTRO_FEATURES</link></filename>
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variable, which is set or appended to in a distribution's configuration file such as
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<filename>poky.conf</filename>,
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<filename>poky-tiny.conf</filename>,
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<filename>poky-lsb.conf</filename> and so forth.
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Machine features are set in the
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<filename><link linkend='var-MACHINE_FEATURES'>MACHINE_FEATURES</link></filename>
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variable, which is set in the machine configuration file and
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specifies the hardware features for a given machine.
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</para>
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<para>
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These two variables combine to work out which kernel modules,
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utilities, and other packages to include.
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A given distribution can support a selected subset of features so some machine features might not
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be included if the distribution itself does not support them.
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</para>
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<para>
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One method you can use to determine which recipes are checking to see if a
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particular feature is contained or not is to <filename>grep</filename> through
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the <link linkend='metadata'>Metadata</link>
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for the feature.
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Here is an example that discovers the recipes whose build is potentially
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changed based on a given feature:
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<literallayout class='monospaced'>
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$ cd poky
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$ git grep 'contains.*MACHINE_FEATURES.*<replaceable>feature</replaceable>'
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</literallayout>
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</para>
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<section id='ref-features-machine'>
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<title>Machine Features</title>
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<para>
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The items below are features you can use with
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<link linkend='var-MACHINE_FEATURES'><filename>MACHINE_FEATURES</filename></link>.
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Features do not have a one-to-one correspondence to packages, and they can
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go beyond simply controlling the installation of a package or packages.
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Sometimes a feature can influence how certain recipes are built.
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For example, a feature might determine whether a particular configure option
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is specified within the
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<link linkend='ref-tasks-configure'><filename>do_configure</filename></link>
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task for a particular recipe.
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</para>
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<para>
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This feature list only represents features as shipped with the Yocto Project metadata:
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<itemizedlist>
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<listitem><para><emphasis>acpi:</emphasis> Hardware has ACPI (x86/x86_64 only)
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</para></listitem>
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<listitem><para><emphasis>alsa:</emphasis> Hardware has ALSA audio drivers
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</para></listitem>
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<listitem><para><emphasis>apm:</emphasis> Hardware uses APM (or APM emulation)
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</para></listitem>
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<listitem><para><emphasis>bluetooth:</emphasis> Hardware has integrated BT
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</para></listitem>
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<listitem><para><emphasis>efi:</emphasis> Support for booting through EFI
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</para></listitem>
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<listitem><para><emphasis>ext2:</emphasis> Hardware HDD or Microdrive
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</para></listitem>
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<listitem><para><emphasis>irda:</emphasis> Hardware has IrDA support
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</para></listitem>
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<listitem><para><emphasis>keyboard:</emphasis> Hardware has a keyboard
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</para></listitem>
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<listitem><para><emphasis>pcbios:</emphasis> Support for booting through BIOS
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</para></listitem>
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<listitem><para><emphasis>pci:</emphasis> Hardware has a PCI bus
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</para></listitem>
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<listitem><para><emphasis>pcmcia:</emphasis> Hardware has PCMCIA or CompactFlash sockets
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</para></listitem>
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<listitem><para><emphasis>phone:</emphasis> Mobile phone (voice) support
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</para></listitem>
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<listitem><para><emphasis>qvga:</emphasis> Machine has a QVGA (320x240) display
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</para></listitem>
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<listitem><para><emphasis>rtc:</emphasis> Machine has a Real-Time Clock
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</para></listitem>
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<listitem><para><emphasis>screen:</emphasis> Hardware has a screen
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</para></listitem>
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<listitem><para><emphasis>serial:</emphasis> Hardware has serial support (usually RS232)
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</para></listitem>
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<listitem><para><emphasis>touchscreen:</emphasis> Hardware has a touchscreen
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</para></listitem>
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<listitem><para><emphasis>usbgadget:</emphasis> Hardware is USB gadget device capable
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</para></listitem>
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<listitem><para><emphasis>usbhost:</emphasis> Hardware is USB Host capable
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</para></listitem>
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<listitem><para><emphasis>vfat:</emphasis> FAT file system support
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</para></listitem>
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<listitem><para><emphasis>wifi:</emphasis> Hardware has integrated WiFi
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='ref-features-distro'>
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<title>Distro Features</title>
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<para>
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The items below are features you can use with
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<link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>
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to enable features across your distribution.
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Features do not have a one-to-one correspondence to packages,
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and they can go beyond simply controlling the installation of a
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package or packages.
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In most cases, the presence or absence of a feature translates to
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the appropriate option supplied to the configure script during the
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<link linkend='ref-tasks-configure'><filename>do_configure</filename></link>
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task for the recipes that optionally
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support the feature.
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</para>
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<para>
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Some distro features are also machine features.
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These select features make sense to be controlled both at
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the machine and distribution configuration level.
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See the
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<link linkend='var-COMBINED_FEATURES'><filename>COMBINED_FEATURES</filename></link>
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variable for more information.
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</para>
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<para>
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This list only represents features as shipped with the Yocto Project metadata:
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<itemizedlist>
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<listitem><para><emphasis>alsa:</emphasis> Include ALSA support
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(OSS compatibility kernel modules installed if available).
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</para></listitem>
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<listitem><para><emphasis>api-documentation:</emphasis>
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Enables generation of API documentation during recipe
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builds.
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The resulting documentation is added to SDK tarballs
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when the
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<filename>bitbake -c populate_sdk</filename> command
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is used.
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See the
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"<ulink url='&YOCTO_DOCS_SDK_URL;#adding-api-documentation-to-the-standard-sdk'>Adding API Documentation to the Standard SDK</ulink>"
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section in the Yocto Project Application Development and
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the Extensible Software Development Kit (eSDK) manual.
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</para></listitem>
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<listitem><para><emphasis>bluetooth:</emphasis> Include
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bluetooth support (integrated BT only).</para></listitem>
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<listitem><para><emphasis>bluez5:</emphasis> Include
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BlueZ Version 5, which provides core Bluetooth layers and
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protocols support.
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<note>
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The default value for the
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<link linkend='var-DISTRO_FEATURES'><filename>DISTRO FEATURES</filename></link>
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variable includes "bluetooth", which causes bluez5
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to be backfilled in for bluetooth support.
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If you do not want bluez5 backfilled and would rather
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use bluez4, you need to use the
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<link linkend='var-DISTRO_FEATURES_BACKFILL_CONSIDERED'><filename>DISTRO_FEATURES_BACKFILL_CONSIDERED</filename></link>
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variable as follows:
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<literallayout class='monospaced'>
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DISTRO_FEATURES_BACKFILL_CONSIDERED = "bluez5"
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</literallayout>
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Setting this variable tells the OpenEmbedded build
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system that you have considered but ruled
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out using the bluez5 feature and that bluez4 will be
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used.
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</note>
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</para></listitem>
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<listitem><para><emphasis>cramfs:</emphasis> Include CramFS
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support.</para></listitem>
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<listitem><para><emphasis>directfb:</emphasis>
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Include DirectFB support.
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</para></listitem>
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<listitem><para><emphasis>ext2:</emphasis> Include tools for
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supporting for devices with internal HDD/Microdrive for
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storing files (instead of Flash only devices).
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</para></listitem>
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<listitem><para><emphasis>ipsec:</emphasis> Include IPSec
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support.</para></listitem>
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<listitem><para><emphasis>ipv6:</emphasis> Include IPv6 support.
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</para></listitem>
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<listitem><para><emphasis>irda:</emphasis> Include IrDA support.
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</para></listitem>
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<listitem><para><emphasis>keyboard:</emphasis> Include keyboard
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support (e.g. keymaps will be loaded during boot).
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</para></listitem>
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<listitem><para><emphasis>ldconfig:</emphasis>
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Include support for ldconfig and
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<filename>ld.so.conf</filename> on the target.
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</para></listitem>
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<listitem><para><emphasis>nfs:</emphasis> Include NFS client
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support (for mounting NFS exports on device).
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</para></listitem>
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<listitem><para><emphasis>opengl:</emphasis>
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Include the Open Graphics Library, which is a
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cross-language, multi-platform application programming
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interface used for rendering two and three-dimensional
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graphics.</para></listitem>
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<listitem><para><emphasis>pci:</emphasis> Include PCI bus
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support.</para></listitem>
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<listitem><para><emphasis>pcmcia:</emphasis> Include
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PCMCIA/CompactFlash support.</para></listitem>
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<listitem><para><emphasis>ppp:</emphasis> Include PPP dialup
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support.</para></listitem>
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<listitem><para><emphasis>ptest:</emphasis> Enables building
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the package tests where supported by individual recipes.
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For more information on package tests, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#testing-packages-with-ptest'>Testing Packages With ptest</ulink>"
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section in the Yocto Project Development Tasks Manual.
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</para></listitem>
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<listitem><para><emphasis>smbfs:</emphasis> Include SMB networks
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client support (for mounting Samba/Microsoft Windows shares
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on device).</para></listitem>
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<listitem><para><emphasis>systemd:</emphasis> Include support
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for this <filename>init</filename> manager, which is a full
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replacement of for <filename>init</filename> with parallel
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starting of services, reduced shell overhead, and other
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features.
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This <filename>init</filename> manager is used by many
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distributions.</para></listitem>
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<listitem><para><emphasis>usbgadget:</emphasis> Include USB
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Gadget Device support (for USB networking/serial/storage).
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</para></listitem>
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<listitem><para><emphasis>usbhost:</emphasis> Include USB Host
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support (allows to connect external keyboard, mouse,
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storage, network etc).</para></listitem>
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<listitem><para><emphasis>wayland:</emphasis> Include the
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Wayland display server protocol and the library that
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supports it.</para></listitem>
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<listitem><para><emphasis>wifi:</emphasis> Include WiFi support
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(integrated only).</para></listitem>
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<listitem><para><emphasis>x11:</emphasis> Include the X server
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and libraries.</para></listitem>
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</itemizedlist>
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</para>
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</section>
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<section id='ref-features-image'>
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<title>Image Features</title>
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<para>
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The contents of images generated by the OpenEmbedded build system
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can be controlled by the
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<link linkend='var-IMAGE_FEATURES'><filename>IMAGE_FEATURES</filename></link>
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and
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<link linkend='var-EXTRA_IMAGE_FEATURES'><filename>EXTRA_IMAGE_FEATURES</filename></link>
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variables that you typically configure in your image recipes.
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Through these variables, you can add several different
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predefined packages such as development utilities or packages with
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debug information needed to investigate application problems or
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profile applications.
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</para>
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<para>
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The following image features are available for all images:
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<itemizedlist>
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<listitem><para><emphasis>allow-empty-password:</emphasis>
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Allows Dropbear and OpenSSH to accept root logins
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and logins from accounts having an empty password string.
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</para></listitem>
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<listitem><para><emphasis>dbg-pkgs:</emphasis>
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Installs debug symbol packages for all packages installed
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in a given image.
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</para></listitem>
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<listitem><para><emphasis>debug-tweaks:</emphasis>
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Makes an image suitable for development (e.g.
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allows root logins without passwords and enables
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post-installation logging).
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See the 'allow-empty-password', 'empty-root-password',
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and 'post-install-logging' features in this list for
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additional information.
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</para></listitem>
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<listitem><para><emphasis>dev-pkgs:</emphasis>
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Installs development packages (headers and extra library
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links) for all packages installed in a given image.
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</para></listitem>
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<listitem><para><emphasis>doc-pkgs:</emphasis> Installs
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documentation packages for all packages installed in a
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given image.
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</para></listitem>
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<listitem><para><emphasis>empty-root-password:</emphasis>
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Sets the root password to an empty string, which allows
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logins with a blank password.
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</para></listitem>
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<listitem><para><emphasis>package-management:</emphasis>
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Installs package management tools and preserves the package
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manager database.
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</para></listitem>
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<listitem><para><emphasis>post-install-logging:</emphasis>
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Enables logging postinstall script runs to
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the <filename>/var/log/postinstall.log</filename> file
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on first boot of the image on the target system.
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<note>
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To make the <filename>/var/log</filename> directory
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on the target persistent, use the
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<link linkend='var-VOLATILE_LOG_DIR'><filename>VOLATILE_LOG_DIR</filename></link>
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variable by setting it to "no".
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</note>
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</para></listitem>
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<listitem><para><emphasis>ptest-pkgs:</emphasis>
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Installs ptest packages for all ptest-enabled recipes.
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</para></listitem>
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<listitem><para><emphasis>read-only-rootfs:</emphasis>
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Creates an image whose root filesystem is read-only.
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See the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-read-only-root-filesystem'>Creating a Read-Only Root Filesystem</ulink>"
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||
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section in the Yocto Project Development Tasks Manual for
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more information.
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</para></listitem>
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<listitem><para><emphasis>splash:</emphasis>
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Enables showing a splash screen during boot.
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By default, this screen is provided by
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<filename>psplash</filename>, which does allow
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customization.
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If you prefer to use an alternative splash screen package,
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you can do so by setting the <filename>SPLASH</filename>
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variable to a different package name (or names) within the
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image recipe or at the distro configuration level.
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|
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</para></listitem>
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|
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<listitem><para><emphasis>staticdev-pkgs:</emphasis>
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Installs static development packages, which are
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static libraries (i.e. <filename>*.a</filename> files), for
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all packages installed in a given image.
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|
|
</para></listitem>
|
||
|
|
</itemizedlist>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Some image features are available only when you inherit the
|
||
|
|
<link linkend='ref-classes-core-image'><filename>core-image</filename></link>
|
||
|
|
class.
|
||
|
|
The current list of these valid features is as follows:
|
||
|
|
<itemizedlist>
|
||
|
|
<listitem><para><emphasis>eclipse-debug:</emphasis> Provides
|
||
|
|
Eclipse remote debugging support.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>hwcodecs:</emphasis> Installs
|
||
|
|
hardware acceleration codecs.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>nfs-server:</emphasis>
|
||
|
|
Installs an NFS server.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>perf:</emphasis>
|
||
|
|
Installs profiling tools such as
|
||
|
|
<filename>perf</filename>, <filename>systemtap</filename>,
|
||
|
|
and <filename>LTTng</filename>.
|
||
|
|
For general information on user-space tools, see the
|
||
|
|
<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-manual'>Yocto Project Application Development and the Extensible Software Development Kit (eSDK)</ulink>
|
||
|
|
manual.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>ssh-server-dropbear:</emphasis>
|
||
|
|
Installs the Dropbear minimal SSH server.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>ssh-server-openssh:</emphasis>
|
||
|
|
Installs the OpenSSH SSH server, which is more
|
||
|
|
full-featured than Dropbear.
|
||
|
|
Note that if both the OpenSSH SSH server and the Dropbear
|
||
|
|
minimal SSH server are present in
|
||
|
|
<filename>IMAGE_FEATURES</filename>, then OpenSSH will take
|
||
|
|
precedence and Dropbear will not be installed.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>tools-debug:</emphasis>
|
||
|
|
Installs debugging tools such as
|
||
|
|
<filename>strace</filename> and <filename>gdb</filename>.
|
||
|
|
For information on GDB, see the
|
||
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#platdev-gdb-remotedebug'>Debugging With the GNU Project Debugger (GDB) Remotely</ulink>"
|
||
|
|
section in the Yocto Project Development Tasks Manual.
|
||
|
|
For information on tracing and profiling, see the
|
||
|
|
<ulink url='&YOCTO_DOCS_PROF_URL;'>Yocto Project Profiling and Tracing Manual</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>tools-sdk:</emphasis>
|
||
|
|
Installs a full SDK that runs on the device.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>tools-testapps:</emphasis>
|
||
|
|
Installs device testing tools (e.g. touchscreen debugging).
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>x11:</emphasis>
|
||
|
|
Installs the X server.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>x11-base:</emphasis>
|
||
|
|
Installs the X server with a minimal environment.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><emphasis>x11-sato:</emphasis>
|
||
|
|
Installs the OpenedHand Sato environment.
|
||
|
|
</para></listitem>
|
||
|
|
</itemizedlist>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='ref-features-backfill'>
|
||
|
|
<title>Feature Backfilling</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Sometimes it is necessary in the OpenEmbedded build system to extend
|
||
|
|
<link linkend='var-MACHINE_FEATURES'><filename>MACHINE_FEATURES</filename></link>
|
||
|
|
or <link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>
|
||
|
|
to control functionality that was previously enabled and not able
|
||
|
|
to be disabled.
|
||
|
|
For these cases, we need to add an
|
||
|
|
additional feature item to appear in one of these variables,
|
||
|
|
but we do not want to force developers who have existing values
|
||
|
|
of the variables in their configuration to add the new feature
|
||
|
|
in order to retain the same overall level of functionality.
|
||
|
|
Thus, the OpenEmbedded build system has a mechanism to
|
||
|
|
automatically "backfill" these added features into existing
|
||
|
|
distro or machine configurations.
|
||
|
|
You can see the list of features for which this is done by
|
||
|
|
finding the
|
||
|
|
<link linkend='var-DISTRO_FEATURES_BACKFILL'><filename>DISTRO_FEATURES_BACKFILL</filename></link>
|
||
|
|
and <link linkend='var-MACHINE_FEATURES_BACKFILL'><filename>MACHINE_FEATURES_BACKFILL</filename></link>
|
||
|
|
variables in the <filename>meta/conf/bitbake.conf</filename> file.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Because such features are backfilled by default into all
|
||
|
|
configurations as described in the previous paragraph, developers
|
||
|
|
who wish to disable the new features need to be able to selectively
|
||
|
|
prevent the backfilling from occurring.
|
||
|
|
They can do this by adding the undesired feature or features to the
|
||
|
|
<link linkend='var-DISTRO_FEATURES_BACKFILL_CONSIDERED'><filename>DISTRO_FEATURES_BACKFILL_CONSIDERED</filename></link>
|
||
|
|
or <link linkend='var-MACHINE_FEATURES_BACKFILL_CONSIDERED'><filename>MACHINE_FEATURES_BACKFILL_CONSIDERED</filename></link>
|
||
|
|
variables for distro features and machine features respectively.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Here are two examples to help illustrate feature backfilling:
|
||
|
|
<itemizedlist>
|
||
|
|
<listitem><para><emphasis>The "pulseaudio" distro feature option</emphasis>:
|
||
|
|
Previously, PulseAudio support was enabled within the Qt and
|
||
|
|
GStreamer frameworks.
|
||
|
|
Because of this, the feature is backfilled and thus
|
||
|
|
enabled for all distros through the
|
||
|
|
<filename>DISTRO_FEATURES_BACKFILL</filename>
|
||
|
|
variable in the <filename>meta/conf/bitbake.conf</filename> file.
|
||
|
|
However, your distro needs to disable the feature.
|
||
|
|
You can disable the feature without affecting
|
||
|
|
other existing distro configurations that need PulseAudio support
|
||
|
|
by adding "pulseaudio" to
|
||
|
|
<filename>DISTRO_FEATURES_BACKFILL_CONSIDERED</filename>
|
||
|
|
in your distro's <filename>.conf</filename> file.
|
||
|
|
Adding the feature to this variable when it also
|
||
|
|
exists in the <filename>DISTRO_FEATURES_BACKFILL</filename>
|
||
|
|
variable prevents the build system from adding the feature to
|
||
|
|
your configuration's <filename>DISTRO_FEATURES</filename>, effectively disabling
|
||
|
|
the feature for that particular distro.</para></listitem>
|
||
|
|
<listitem><para><emphasis>The "rtc" machine feature option</emphasis>:
|
||
|
|
Previously, real time clock (RTC) support was enabled for all
|
||
|
|
target devices.
|
||
|
|
Because of this, the feature is backfilled and thus enabled
|
||
|
|
for all machines through the <filename>MACHINE_FEATURES_BACKFILL</filename>
|
||
|
|
variable in the <filename>meta/conf/bitbake.conf</filename> file.
|
||
|
|
However, your target device does not have this capability.
|
||
|
|
You can disable RTC support for your device without
|
||
|
|
affecting other machines that need RTC support
|
||
|
|
by adding the feature to your machine's
|
||
|
|
<filename>MACHINE_FEATURES_BACKFILL_CONSIDERED</filename>
|
||
|
|
list in the machine's <filename>.conf</filename> file.
|
||
|
|
Adding the feature to this variable when it also
|
||
|
|
exists in the <filename>MACHINE_FEATURES_BACKFILL</filename>
|
||
|
|
variable prevents the build system from adding the feature to
|
||
|
|
your configuration's <filename>MACHINE_FEATURES</filename>, effectively
|
||
|
|
disabling RTC support for that particular machine.</para></listitem>
|
||
|
|
</itemizedlist>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</chapter>
|
||
|
|
|
||
|
|
<!--
|
||
|
|
vim: expandtab tw=80 ts=4 spell spelllang=en_gb
|
||
|
|
-->
|