import-layers/yocto-poky/documentation/bsp-guide/bsp.xml

<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

<chapter id='bsp'>

        <title>Board Support Packages (BSP) - Developer's Guide</title>

        <para>
            A Board Support Package (BSP) is a collection of information that
            defines how to support a particular hardware device, set of devices, or
            hardware platform.
            The BSP includes information about the hardware features
            present on the device and kernel configuration information along with any
            additional hardware drivers required.
            The BSP also lists any additional software
            components required in addition to a generic Linux software stack for both
            essential and optional platform features.
        </para>

        <para>
            This guide presents information about BSP Layers, defines a structure for components
            so that BSPs follow a commonly understood layout, discusses how to customize
            a recipe for a BSP, addresses BSP licensing, and provides information that
            shows you how to create and manage a
            <link linkend='bsp-layers'>BSP Layer</link> using two Yocto Project
            <link linkend='using-the-yocto-projects-bsp-tools'>BSP Tools</link>.
        </para>

        <section id='bsp-layers'>
            <title>BSP Layers</title>

            <para>
                A BSP consists of a file structure inside a base directory.
                Collectively, you can think of the base directory, its file structure,
                and the contents as a BSP Layer.
                Although not a strict requirement, layers in the Yocto Project use the
                following well-established naming convention:
                <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>
                </literallayout>
                The string "meta-" is prepended to the machine or platform name, which is
                <replaceable>bsp_name</replaceable> in the above form.
                <note><title>Tip</title>
                    Because the BSP layer naming convention is well-established,
                    it is advisable to follow it when creating layers.
                    Technically speaking, a BSP layer name does not need to
                    start with <filename>meta-</filename>.
                    However, you might run into situations where obscure
                    scripts assume this convention.
                </note>
            </para>

            <para>
                To help understand the BSP layer concept, consider the BSPs that the
                Yocto Project supports and provides with each release.
                You can see the layers in the
                <ulink url='&YOCTO_DOCS_REF_URL;#yocto-project-repositories'>Yocto Project Source Repositories</ulink>
                through a web interface at
                <ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi'></ulink>.
                If you go to that interface, you will find near the bottom of the list
                under "Yocto Metadata Layers" several BSP layers all of which are
                supported by the Yocto Project (e.g. <filename>meta-raspberrypi</filename> and
                <filename>meta-intel</filename>).
                Each of these layers is a repository unto itself and clicking on a
                layer reveals information that includes two links from which you can choose
                to set up a clone of the layer's repository on your local host system.
                Here is an example that clones the Raspberry Pi BSP layer:
                <literallayout class='monospaced'>
     $ git clone git://git.yoctoproject.org/meta-raspberrypi
                </literallayout>
            </para>

            <para>
                In addition to BSP layers near the bottom of that referenced
                Yocto Project Source Repository, the
                <filename>meta-yocto-bsp</filename> layer is part of the
                shipped <filename>poky</filename> repository.
                The <filename>meta-yocto-bsp</filename> layer maintains several
                BSPs such as the Beaglebone, EdgeRouter, and generic versions of
                both 32 and 64-bit IA machines.
            </para>

            <para>
                For information on the BSP development workflow, see the
                "<link linkend='developing-a-board-support-package-bsp'>Developing a Board Support Package (BSP)</link>"
                section.
                For more information on how to set up a local copy of source files
                from a Git repository, see the
                "<ulink url='&YOCTO_DOCS_DEV_URL;#working-with-yocto-project-source-files'>Working With Yocto Project Source Files</ulink>"
                section also in the Yocto Project Development Tasks Manual.
            </para>

            <para>
                The layer's base directory
                (<filename>meta-<replaceable>bsp_name</replaceable></filename>)
                is the root of the BSP Layer.
                This root is what you add to the
                <ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
                variable in the <filename>conf/bblayers.conf</filename> file found in the
                <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
                which is established after you run the OpenEmbedded build environment
                setup script (i.e.
                <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>).
                Adding the root allows the OpenEmbedded build system to recognize the BSP
                definition and from it build an image.
                Here is an example:
                <literallayout class='monospaced'>
     BBLAYERS ?= " \
       /usr/local/src/yocto/meta \
       /usr/local/src/yocto/meta-poky \
       /usr/local/src/yocto/meta-yocto-bsp \
       /usr/local/src/yocto/meta-mylayer \
       "
                </literallayout>
            </para>

            <para>
                Some BSPs require additional layers on
                top of the BSP's root layer in order to be functional.
                For these cases, you also need to add those layers to the
                <filename>BBLAYERS</filename> variable in order to build the BSP.
                You must also specify in the "Dependencies" section of the BSP's
                <filename>README</filename> file any requirements for additional
                layers and, preferably, any
                build instructions that might be contained elsewhere
                in the <filename>README</filename> file.
            </para>

            <para>
                Some layers function as a layer to hold other BSP layers.
                An example of this type of layer is the <filename>meta-intel</filename> layer,
                which contains a number of individual BSP sub-layers, as well as a directory
                named <filename>common/</filename> full of common content across those layers.
                Another example is the <filename>meta-yocto-bsp</filename> layer mentioned
                earlier.
            </para>

            <para>
                For more detailed information on layers, see the
                "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
                section of the Yocto Project Development Tasks Manual.
            </para>
        </section>

        <section id='preparing-your-build-host-to-work-with-bsp-layers'>
            <title>Preparing Your Build Host to Work With BSP Layers</title>

            <para>
                This section describes how to get your build host ready
                to work with BSP layers.
                Once you have the host set up, you can create the layer
                as described in the
                "<link linkend='creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a new BSP Layer Using the yocto-bsp Script</link>"
                section.
                <note>
                    For structural information on BSPs, see the
                    <link linkend='bsp-filelayout'>Example Filesystem Layout</link>
                    section.
                </note>
                <orderedlist>
                    <listitem><para>
                        <emphasis>Set Up the Build Environment:</emphasis>
                        Be sure you are set up to use BitBake in a shell.
                        See the
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#setting-up-the-development-host-to-use-the-yocto-project'>Setting Up the Development Host to Use the Yocto Project</ulink>"
                        section in the Yocto Project Development Tasks Manual for information
                        on how to get a build host ready that is either a native
                        Linux machine or a machine that uses CROPS.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Clone the <filename>poky</filename> Repository:</emphasis>
                        You need to have a local copy of the Yocto Project
                        <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
                        (i.e. a local <filename>poky</filename> repository).
                        See the
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#cloning-the-poky-repository'>Cloning the <filename>poky</filename> Repository</ulink>"
                        and possibly the
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking Out by Branch in Poky</ulink>"
                        and
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#checkout-out-by-tag-in-poky'>Checking Out by Tag in Poky</ulink>"
                        sections all in the Yocto Project Development Tasks Manual for
                        information on how to clone the <filename>poky</filename>
                        repository and check out the appropriate branch for your work.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Determine the BSP Layer You Want:</emphasis>
                        The Yocto Project supports many BSPs, which are maintained in
                        their own layers or in layers designed to contain several
                        BSPs.
                        To get an idea of machine support through BSP layers, you can
                        look at the
                        <ulink url='&YOCTO_RELEASE_DL_URL;/machines'>index of machines</ulink>
                        for the release.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Optionally Clone the
                        <filename>meta-intel</filename> BSP Layer:</emphasis>
                        If your hardware is based on current Intel CPUs and devices,
                        you can leverage this BSP layer.
                        For details on the <filename>meta-intel</filename> BSP layer,
                        see the layer's
                        <ulink url='http://git.yoctoproject.org/cgit/cgit.cgi/meta-intel/tree/README'><filename>README</filename></ulink>
                        file.
                        <orderedlist>
                            <listitem><para>
                                <emphasis>Navigate to Your Source Directory:</emphasis>
                                Typically, you set up the
                                <filename>meta-intel</filename> Git repository
                                inside the
                                <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
                                (e.g. <filename>poky</filename>).
                                </para></listitem>
                            <listitem><para>
                                <emphasis>Clone the Layer:</emphasis>
                                <literallayout class='monospaced'>
     $ git clone git://git.yoctoproject.org/meta-intel.git
     Cloning into 'meta-intel'...
     remote: Counting objects: 14224, done.
     remote: Compressing objects: 100% (4591/4591), done.
     remote: Total 14224 (delta 8245), reused 13985 (delta 8006)
     Receiving objects: 100% (14224/14224), 4.29 MiB | 2.90 MiB/s, done.
     Resolving deltas: 100% (8245/8245), done.
     Checking connectivity... done.
                                </literallayout>
                                </para></listitem>
                            <listitem><para>
                                <emphasis>Check Out the Proper Branch:</emphasis>
                                The branch you check out for
                                <filename>meta-intel</filename> must match the same
                                branch you are using for the Yocto Project release
                                (e.g. &DISTRO_NAME_NO_CAP;):
                                <literallayout class='monospaced'>
     $ git checkout <replaceable>branch_name</replaceable>
                                </literallayout>
                                For an example on how to discover branch names and
                                checkout on a branch, see the
                                "<ulink url='&YOCTO_DOCS_DEV_URL;#checking-out-by-branch-in-poky'>Checking Out By Branch in Poky</ulink>"
                                section in the Yocto Project Development Tasks Manual.
                                </para></listitem>
                        </orderedlist>
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Optionally Set Up an Alternative BSP Layer:</emphasis>
                        If your hardware can be more closely leveraged to an
                        existing BSP not within the <filename>meta-intel</filename>
                        BSP layer, you can clone that BSP layer.</para>

                        <para>The process is identical to the process used for the
                        <filename>meta-intel</filename> layer except for the layer's
                        name.
                        For example, if you determine that your hardware most
                        closely matches the <filename>meta-minnow</filename>,
                        clone that layer:
                        <literallayout class='monospaced'>
     $ git clone git://git.yoctoproject.org/meta-minnow
     Cloning into 'meta-minnow'...
     remote: Counting objects: 456, done.
     remote: Compressing objects: 100% (283/283), done.
     remote: Total 456 (delta 163), reused 384 (delta 91)
     Receiving objects: 100% (456/456), 96.74 KiB | 0 bytes/s, done.
     Resolving deltas: 100% (163/163), done.
     Checking connectivity... done.
                        </literallayout>
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Initialize the Build Environment:</emphasis>
                        While in the root directory of the Source Directory (i.e.
                        <filename>poky</filename>), run the
                        <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
                        environment setup script to define the OpenEmbedded
                        build environment on your build host.
                        <literallayout class='monospaced'>
     $ source &OE_INIT_FILE;
                        </literallayout>
                        Among other things, the script creates the
                        <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
                        which is <filename>build</filename> in this case
                        and is located in the
                        <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.
                        After the script runs, your current working directory
                        is set to the <filename>build</filename> directory.
                        </para></listitem>
                </orderedlist>
            </para>
        </section>

        <section id="bsp-filelayout">
            <title>Example Filesystem Layout</title>

            <para>
                Defining a common BSP directory structure allows end-users to understand and
                become familiar with that structure.
                A common format also encourages standardization of software support of hardware.
            </para>

            <para>
                The proposed form does have elements that are specific to the
                OpenEmbedded build system.
                It is intended that this information can be
                used by other build systems besides the OpenEmbedded build system
                and that it will be simple
                to extract information and convert it to other formats if required.
                The OpenEmbedded build system, through its standard layers mechanism, can directly
                accept the format described as a layer.
                The BSP captures all
                the hardware-specific details in one place in a standard format, which is
                useful for any person wishing to use the hardware platform regardless of
                the build system they are using.
            </para>

            <para>
                The BSP specification does not include a build system or other tools -
                it is concerned with the hardware-specific components only.
                At the end-distribution point, you can ship the BSP combined with a build system
                and other tools.
                However, it is important to maintain the distinction that these
                are separate components that happen to be combined in certain end products.
            </para>

            <para>
                Before looking at the common form for the file structure inside a BSP Layer,
                you should be aware that some requirements do exist in order for a BSP to
                be considered compliant with the Yocto Project.
                For that list of requirements, see the
                "<link linkend='released-bsp-requirements'>Released BSP Requirements</link>"
                section.
            </para>

            <para>
                Below is the common form for the file structure inside a BSP Layer.
                While you can use this basic form for the standard, realize that the actual structures
                for specific BSPs could differ.

                <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/
     meta-<replaceable>bsp_name</replaceable>/<replaceable>bsp_license_file</replaceable>
     meta-<replaceable>bsp_name</replaceable>/README
     meta-<replaceable>bsp_name</replaceable>/README.sources
     meta-<replaceable>bsp_name</replaceable>/binary/<replaceable>bootable_images</replaceable>
     meta-<replaceable>bsp_name</replaceable>/conf/layer.conf
     meta-<replaceable>bsp_name</replaceable>/conf/machine/*.conf
     meta-<replaceable>bsp_name</replaceable>/recipes-bsp/*
     meta-<replaceable>bsp_name</replaceable>/recipes-core/*
     meta-<replaceable>bsp_name</replaceable>/recipes-graphics/*
     meta-<replaceable>bsp_name</replaceable>/recipes-kernel/linux/linux-yocto_<replaceable>kernel_rev</replaceable>.bbappend
                </literallayout>
            </para>

            <para>
                Below is an example of the Raspberry Pi BSP:

                <literallayout class='monospaced'>
     meta-raspberrypi/COPYING.MIT
     meta-raspberrypi/README
     meta-raspberrypi/classes
     meta-raspberrypi/classes/linux-raspberrypi-base.bbclass
     meta-raspberrypi/classes/sdcard_image-rpi.bbclass
     meta-raspberrypi/conf/
     meta-raspberrypi/conf/layer.conf
     meta-raspberrypi/conf/machine/
     meta-raspberrypi/conf/machine/raspberrypi.conf
     meta-raspberrypi/conf/machine/raspberrypi0.conf
     meta-raspberrypi/conf/machine/raspberrypi2.conf
     meta-raspberrypi/conf/machine/raspberrypi3.conf
     meta-raspberrypi/conf/machine/include
     meta-raspberrypi/conf/machine/include/rpi-base.inc
     meta-raspberrypi/conf/machine/include/rpi-default-providers.inc
     meta-raspberrypi/conf/machine/include/rpi-default-settings.inc
     meta-raspberrypi/conf/machine/include/rpi-default-versions.inc
     meta-raspberrypi/conf/machine/include/rpi-tune-arm1176jzf-s.inc
     meta-raspberrypi/files
     meta-raspberrypi/files/custom-licenses
     meta-raspberrypi/files/custom-licenses/Broadcom
     meta-raspberrypi/recipes-bsp
     meta-raspberrypi/recipes-bsp/bootfiles
     meta-raspberrypi/recipes-bsp/bootfiles/bcm2835-bootfiles.bb
     meta-raspberrypi/recipes-bsp/bootfiles/rpi-config_git.bb
     meta-raspberrypi/recipes-bsp/common
     meta-raspberrypi/recipes-bsp/common/firmware.inc
     meta-raspberrypi/recipes-bsp/formfactor_00.bbappend
     meta-raspberrypi/recipes-bsp/formfactor/raspberrypi/machconfig
     meta-raspberrypi/recipes-bsp/rpi-mkimage_git.bb
     meta-raspberrypi/recipes-bsp/rpi-mkimage/License
     meta-raspberrypi/recipes-bsp/rpi-mkimage/open-files-relative-to-script.patch
     meta-raspberrypi/recipes-bsp/u-boot/u-boot-rpi_git.bb
     meta-raspberrypi/recipes-core
     meta-raspberrypi/recipes-core/images
     meta-raspberrypi/recipes-core/images/rpi-basic-image.bb
     meta-raspberrypi/recipes-core/images/rpi-hwup-image.bb
     meta-raspberrypi/recipes-core/images/rpi-test-image.bb
     meta-raspberrypi/recipes-core/packagegroups
     meta-raspberrypi/recipes-core/packagegroups/packagegroup-rpi-test.bb
     meta-raspberrypi/recipes-core/psplash
     meta-raspberrypi/recipes-core/psplash/files
     meta-raspberrypi/recipes-core/psplash/psplash_git.bbappend
     meta-raspberrypi/recipes-core/psplash/files/psplash-raspberrypi-img.h
     meta-raspberrypi/recipes-devtools
     meta-raspberrypi/recipes-devtools/bcm2835
     meta-raspberrypi/recipes-devtools/bcm2835/bcm2835_1.46.bb
     meta-raspberrypi/recipes-devtools/pi-blaster
     meta-raspberrypi/recipes-devtools/pi-blaster/files
     meta-raspberrypi/recipes-devtools/pi-blaster/*.patch
     meta-raspberrypi/recipes-devtools/pi-blaster/pi-blaster.inc
     meta-raspberrypi/recipes-devtools/pi-blaster/pi-blaster_git.bb
     meta-raspberrypi/recipes-devtools/python
     meta-raspberrypi/recipes-devtools/python/python-rtimu
     meta-raspberrypi/recipes-devtools/python/python-rtimu/*.patch
     meta-raspberrypi/recipes-devtools/python/python-rtimu_git.bb
     meta-raspberrypi/recipes-devtools/python/python-sense-hat_2.1.0.bb
     meta-raspberrypi/recipes-devtools/python/rpi-gpio
     meta-raspberrypi/recipes-devtools/python/rpi-gpio/*.patch
     meta-raspberrypi/recipes-devtools/python/rpi-gpio_0.6.1.bb
     meta-raspberrypi/recipes-devtools/python/rpio
     meta-raspberrypi/recipes-devtools/python/rpio/*.patch
     meta-raspberrypi/recipes-devtools/python/rpio_0.10.0.bb
     meta-raspberrypi/recipes-devtools/wiringPi
     meta-raspberrypi/recipes-devtools/wiringPi/files
     meta-raspberrypi/recipes-devtools/wiringPi/files/*.patch
     meta-raspberrypi/recipes-devtools/wiringPi/wiringpi
     meta-raspberrypi/recipes-devtools/wiringPi/wiringpi/*.patch
     meta-raspberrypi/recipes-devtools/wiringPi/wiringpi_git.bb
     meta-raspberrypi/recipes-graphics
     meta-raspberrypi/recipes-graphics/eglinfo
     meta-raspberrypi/recipes-graphics/eglinfo/eglinfo-fb_%.bbappend
     meta-raspberrypi/recipes-graphics/eglinfo/eglinfo-x11_%.bbappend
     meta-raspberrypi/recipes-graphics/userland
     meta-raspberrypi/recipes-graphics/userland/userland
     meta-raspberrypi/recipes-graphics/userland/userland/*.patch
     meta-raspberrypi/recipes-graphics/userland/userland_git.bb
     meta-raspberrypi/recipes-graphics/vc-graphics
     meta-raspberrypi/recipes-graphics/vc-graphics/files
     meta-raspberrypi/recipes-graphics/vc-graphics/files/egl.pc
     meta-raspberrypi/recipes-graphics/vc-graphics/files/vchiq.sh
     meta-raspberrypi/recipes-graphics/vc-graphics/vc-graphics-hardfp.bb
     meta-raspberrypi/recipes-graphics/vc-graphics/vc-graphics.bb
     meta-raspberrypi/recipes-graphics/vc-graphics/vc-graphics.inc
     meta-raspberrypi/recipes-graphics/wayland
     meta-raspberrypi/recipes-graphics/wayland/weston_%.bbappend
     meta-raspberrypi/recipes-graphics/weston
     meta-raspberrypi/recipes-graphics/weston/weston_%.bbappend
     meta-raspberrypi/recipes-graphics/xorg-xserver
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d/10-evdev.conf
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config/rpi/xorg.conf.d/99-pitft.conf
     meta-raspberrypi/recipes-graphics/xorg-xserver/xserver-xf86-config_0.1.bbappend
     meta-raspberrypi/recipes-kernel
     meta-raspberrypi/recipes-kernel/linux-firmware
     meta-raspberrypi/recipes-kernel/linux-firmware/linux-firmware
     meta-raspberrypi/recipes-kernel/linux-firmware/linux-firmware/LICENSE.broadcom_brcm80211
     meta-raspberrypi/recipes-kernel/linux-firmware/linux-firmware/brcmfmac43430-sdio.bin
     meta-raspberrypi/recipes-kernel/linux-firmware/linux-firmware/brcmfmac43430-sdio.txt
     meta-raspberrypi/recipes-kernel/linux-firmware/linux-firmware_git.bbappend
     meta-raspberrypi/recipes-kernel/linux
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-3.14
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-3.14/*.patch
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-3.18
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-3.18/*.patch
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-4.1
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi-4.1/*.patch
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi.inc
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi/defconfig
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi_3.14.bb
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi_3.18.bb
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi_4.1.bb
     meta-raspberrypi/recipes-kernel/linux/linux-raspberrypi_4.4.bb
     meta-raspberrypi/recipes-kernel/linux/linux.inc
     meta-raspberrypi/recipes-multimedia
     meta-raspberrypi/recipes-multimedia/gstreamer
     meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx
     meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx/*.patch
     meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-omx_%.bbappend
     meta-raspberrypi/recipes-multimedia/gstreamer/gstreamer1.0-plugins-bad_%.bbappend
     meta-raspberrypi/recipes-multimedia/omxplayer
     meta-raspberrypi/recipes-multimedia/omxplayer/omxplayer
     meta-raspberrypi/recipes-multimedia/omxplayer/omxplayer/*.patch
     meta-raspberrypi/recipes-multimedia/omxplayer/omxplayer_git.bb
     meta-raspberrypi/scripts
     meta-raspberrypi/scripts/lib
     meta-raspberrypi/scripts/lib/image
     meta-raspberrypi/scripts/lib/image/canned-wks
     meta-raspberrypi/scripts/lib/image/canned-wks/sdimage-raspberrypi.wks
                </literallayout>
            </para>

            <para>
                The following sections describe each part of the proposed BSP format.
            </para>

            <section id="bsp-filelayout-license">
                <title>License Files</title>

                <para>
                    You can find these files in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/<replaceable>bsp_license_file</replaceable>
                    </literallayout>
                </para>

                <para>
                    These optional files satisfy licensing requirements for the BSP.
                    The type or types of files here can vary depending on the licensing requirements.
                    For example, in the Raspberry Pi BSP all licensing requirements are handled with the
                    <filename>COPYING.MIT</filename> file.
                </para>

                <para>
                    Licensing files can be MIT, BSD, GPLv*, and so forth.
                    These files are recommended for the BSP but are optional and totally up to the BSP developer.
                </para>
            </section>

            <section id="bsp-filelayout-readme">
                <title>README File</title>

                <para>
                    You can find this file in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/README
                    </literallayout>
                </para>

                <para>
                    This file provides information on how to boot the live images that are optionally
                    included in the <filename>binary/</filename> directory.
                    The <filename>README</filename> file also provides special information needed for
                    building the image.
                </para>

                <para>
                    At a minimum, the <filename>README</filename> file must
                    contain a list of dependencies, such as the names of
                    any other layers on which the BSP depends and the name of
                    the BSP maintainer with his or her contact information.
                </para>
            </section>

            <section id="bsp-filelayout-readme-sources">
                <title>README.sources File</title>

                <para>
                    You can find this file in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/README.sources
                    </literallayout>
                </para>

                <para>
                    This file provides information on where to locate the BSP
                    source files used to build the images (if any) that reside in
                    <filename>meta-<replaceable>bsp_name</replaceable>/binary</filename>.
                    Images in the <filename>binary</filename> would be images
                    released with the BSP.
                    The information in the <filename>README.sources</filename>
                    file also helps you find the
                    <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink>
                    used to generate the images that ship with the BSP.
                    <note>
                        If the BSP's <filename>binary</filename> directory is
                        missing or the directory has no images, an existing
                        <filename>README.sources</filename> file is
                        meaningless.
                    </note>
                </para>
            </section>

            <section id="bsp-filelayout-binary">
                <title>Pre-built User Binaries</title>

                <para>
                    You can find these files in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/binary/<replaceable>bootable_images</replaceable>
                    </literallayout>
                </para>

                <para>
                    This optional area contains useful pre-built kernels and
                    user-space filesystem images released with the BSP that are
                    appropriate to the target system.
                    This directory typically contains graphical (e.g. Sato) and
                    minimal live images when the BSP tarball has been created and
                    made available in the
                    <ulink url='&YOCTO_HOME_URL;'>Yocto Project</ulink> website.
                    You can use these kernels and images to get a system running
                    and quickly get started on development tasks.
                </para>

                <para>
                    The exact types of binaries present are highly
                    hardware-dependent.
                    The <filename>README</filename> file should be present in the
                    BSP Layer and it will explain how to use the images with the
                    target hardware.
                    Additionally, the <filename>README.sources</filename> file
                    should be present to locate the sources used to build the
                    images and provide information on the Metadata.
                </para>
            </section>

            <section id='bsp-filelayout-layer'>
                <title>Layer Configuration File</title>

                <para>
                    You can find this file in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/conf/layer.conf
                    </literallayout>
                </para>

                <para>
                    The <filename>conf/layer.conf</filename> file identifies the file structure as a
                    layer, identifies the
                    contents of the layer, and contains information about how the build
                    system should use it.
                    Generally, a standard boilerplate file such as the following works.
                    In the following example, you would replace "<replaceable>bsp</replaceable>" and
                    "<replaceable>_bsp</replaceable>" with the actual name
                    of the BSP (i.e. <replaceable>bsp_name</replaceable> from the example template).
                </para>

                <para>
                   <literallayout class='monospaced'>
     # We have a conf and classes directory, add to BBPATH
     BBPATH .= ":${LAYERDIR}"

     # We have a recipes directory, add to BBFILES
     BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
                 ${LAYERDIR}/recipes-*/*/*.bbappend"

     BBFILE_COLLECTIONS += "<replaceable>bsp</replaceable>"
     BBFILE_PATTERN_<replaceable>bsp</replaceable> = "^${LAYERDIR}/"
     BBFILE_PRIORITY_<replaceable>bsp</replaceable> = "6"

     LAYERDEPENDS_<replaceable>bsp</replaceable> = "intel"
                    </literallayout>
                </para>

                <para>
                    To illustrate the string substitutions, here are the corresponding statements
                    from the Raspberry Pi <filename>conf/layer.conf</filename> file:
                   <literallayout class='monospaced'>
     # We have a conf and classes directory, append to BBPATH
     BBPATH .= ":${LAYERDIR}"

     # We have a recipes directory containing .bb and .bbappend files, add to BBFILES
     BBFILES += "${LAYERDIR}/recipes*/*/*.bb \
                 ${LAYERDIR}/recipes*/*/*.bbappend"

     BBFILE_COLLECTIONS += "raspberrypi"
     BBFILE_PATTERN_raspberrypi := "^${LAYERDIR}/"
     BBFILE_PRIORITY_raspberrypi = "9"

     # Additional license directories.
     LICENSE_PATH += "${LAYERDIR}/files/custom-licenses"
                    </literallayout>
                </para>

                <para>
                    This file simply makes
                    <ulink url='&YOCTO_DOCS_REF_URL;#bitbake-term'>BitBake</ulink>
                    aware of the recipes and configuration directories.
                    The file must exist so that the OpenEmbedded build system can recognize the BSP.
                </para>
            </section>

            <section id="bsp-filelayout-machine">
                <title>Hardware Configuration Options</title>

                <para>
                    You can find these files in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/conf/machine/*.conf
                    </literallayout>
                </para>

                <para>
                    The machine files bind together all the information contained elsewhere
                    in the BSP into a format that the build system can understand.
                    If the BSP supports multiple machines, multiple machine configuration files
                    can be present.
                    These filenames correspond to the values to which users have set the
                    <ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink> variable.
                </para>

                <para>
                    These files define things such as the kernel package to use
                    (<ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_PROVIDER'><filename>PREFERRED_PROVIDER</filename></ulink>
                    of virtual/kernel), the hardware drivers to
                    include in different types of images, any special software components
                    that are needed, any bootloader information, and also any special image
                    format requirements.
                </para>

                <para>
                    Each BSP Layer requires at least one machine file.
                    However, you can supply more than one file.
                </para>

                <para>
                    This configuration file could also include a hardware "tuning"
                    file that is commonly used to define the package architecture
                    and specify optimization flags, which are carefully chosen
                    to give best performance on a given processor.
                </para>

                <para>
                    Tuning files are found in the <filename>meta/conf/machine/include</filename>
                    directory within the
                    <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.
                    For example, the <filename>ia32-base.inc</filename> file resides in the
                    <filename>meta/conf/machine/include</filename> directory.
                </para>

                <para>
                    To use an include file, you simply include them in the
                    machine configuration file.
                    For example, the Raspberry Pi BSP
                    <filename>raspberrypi3.conf</filename> contains the
                    following statement:
                    <literallayout class='monospaced'>
     include conf/machine/raspberrypi2.conf
                    </literallayout>
                </para>
            </section>

            <section id='bsp-filelayout-misc-recipes'>
                <title>Miscellaneous BSP-Specific Recipe Files</title>

                <para>
                    You can find these files in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/recipes-bsp/*
                    </literallayout>
                </para>

                <para>
                    This optional directory contains miscellaneous recipe files for
                    the BSP.
                    Most notably would be the formfactor files.
                    For example, in the Raspberry Pi BSP there is the
                    <filename>formfactor_0.0.bbappend</filename> file, which is an
                    append file used to augment the recipe that starts the build.
                    Furthermore, there are machine-specific settings used during
                    the build that are defined by the
                    <filename>machconfig</filename> file further down in the
                    directory.
                    Here is the <filename>machconfig</filename>
                    file for the Raspberry Pi BSP:
                    <literallayout class='monospaced'>
     HAVE_TOUCHSCREEN=0
     HAVE_KEYBOARD=1

     DISPLAY_CAN_ROTATE=0
     DISPLAY_ORIENTATION=0
     DISPLAY_DPI=133
                    </literallayout>
                </para>

                <note><para>
                    If a BSP does not have a formfactor entry, defaults are established according to
                    the formfactor configuration file that is installed by the main
                    formfactor recipe
                    <filename>meta/recipes-bsp/formfactor/formfactor_0.0.bb</filename>,
                    which is found in the
                    <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.
                </para></note>
            </section>

            <section id='bsp-filelayout-recipes-graphics'>
                <title>Display Support Files</title>

                <para>
                    You can find these files in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/recipes-graphics/*
                    </literallayout>
                </para>

                <para>
                    This optional directory contains recipes for the BSP if it has
                    special requirements for graphics support.
                    All files that are needed for the BSP to support a display are
                    kept here.
                </para>
            </section>

            <section id='bsp-filelayout-kernel'>
                <title>Linux Kernel Configuration</title>

                <para>
                    You can find these files in the BSP Layer at:
                    <literallayout class='monospaced'>
     meta-<replaceable>bsp_name</replaceable>/recipes-kernel/linux/linux-yocto*.bbappend
                    </literallayout>
                </para>

                <para>
                    These files append machine-specific changes to the main
                    kernel recipe you are using.
                </para>

                <para>
                    For your BSP, you typically want to use an existing Yocto
                    Project kernel recipe found in the
                    <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
                    at <filename>meta/recipes-kernel/linux</filename>.
                    You can append machine-specific changes to the kernel recipe
                    by using a similarly named append file, which is located in
                    the BSP Layer for your target device (e.g. the
                    <filename>meta-<replaceable>bsp_name</replaceable>/recipes-kernel/linux</filename> directory).
                </para>

                <para>
                    Suppose you are using the <filename>linux-yocto_4.4.bb</filename>
                    recipe to build the kernel.
                    In other words, you have selected the kernel in your
                    <replaceable>bsp_name</replaceable><filename>.conf</filename>
                    file by adding
                    <ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_PROVIDER'><filename>PREFERRED_PROVIDER</filename></ulink>
                    and
                    <ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></ulink>
                    statements as follows:
                    <literallayout class='monospaced'>
     PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
     PREFERRED_VERSION_linux-yocto ?= "4.4%"
                    </literallayout>
                    <note>
                        When the preferred provider is assumed by default, the
                        <filename>PREFERRED_PROVIDER</filename>
                        statement does not appear in the
                        <replaceable>bsp_name</replaceable><filename>.conf</filename> file.
                    </note>
                    You would use the <filename>linux-yocto_4.4.bbappend</filename>
                    file to append specific BSP settings to the kernel, thus
                    configuring the kernel for your particular BSP.
                </para>

                <para>
                    You can find more information on what your append file
                    should contain in the
                    "<ulink url='&YOCTO_DOCS_KERNEL_URL;#creating-the-append-file'>Creating the Append File</ulink>"
                    section in the Yocto Project Linux Kernel Development
                    Manual.
                </para>
            </section>
        </section>

        <section id='developing-a-board-support-package-bsp'>
            <title>Developing a Board Support Package (BSP)</title>

            <para>
                This section contains the high-level procedure you can follow
                to create a BSP using the Yocto Project's
                <link linkend='using-the-yocto-projects-bsp-tools'>BSP Tools</link>.
                Although not required for BSP creation, the
                <filename>meta-intel</filename> repository, which contains
                many BSPs supported by the Yocto Project, is part of the
                example.
            </para>

            <para>
                For an example that shows how to create a new layer using
                the tools, see the
                "<link linkend='creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</link>"
                 section.
            </para>

            <para>
                The following illustration and list summarize the BSP
                creation general workflow.
            </para>

            <para>
                <imagedata fileref="figures/bsp-dev-flow.png" width="7in" depth="5in" align="center" scalefit="1" />
            </para>

            <para>
                <orderedlist>
                    <listitem><para>
                        <emphasis>Set up Your Host Development System to Support
                        Development Using the Yocto Project</emphasis>:
                        See the
                        "<ulink url='&YOCTO_DOCS_QS_URL;#yp-resources'>Setting Up to Use the Yocto Project</ulink>"
                        section in the Yocto Project Quick Start for options on how
                        to get a build host ready to use the Yocto Project.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Establish the <filename>meta-intel</filename>
                        Repository on Your System:</emphasis>
                        Having local copies of these supported BSP layers on
                        your system gives you access to layers you might be able
                        to build on or modify to create your BSP.
                        For information on how to get these files, see the
                        "<link linkend='preparing-your-build-host-to-work-with-bsp-layers'>Preparing Your Build Host to Work with BSP Layers</link>"
                        section.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Create Your Own BSP Layer Using the
                        <link linkend='creating-a-new-bsp-layer-using-the-yocto-bsp-script'><filename>yocto-bsp</filename></link>
                        script:</emphasis>
                        Layers are ideal for isolating and storing work for a
                        given piece of hardware.
                        A layer is really just a location or area in which you
                        place the recipes and configurations for your BSP.
                        In fact, a BSP is, in itself, a special type of layer.
                        The simplest way to create a new BSP layer that is
                        compliant with the Yocto Project is to use the
                        <filename>yocto-bsp</filename> script.
                        For information about that script, see the
                        "<link linkend='creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</link>"
                        section.</para>

                        <para>Another example that illustrates a layer
                        is an application.
                        Suppose you are creating an application that has
                        library or other dependencies in order for it to
                        compile and run.
                        The layer, in this case, would be where all the
                        recipes that define those dependencies are kept.
                        The key point for a layer is that it is an isolated
                        area that contains all the relevant information for
                        the project that the OpenEmbedded build system knows
                        about.
                        For more information on layers, see the
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
                        section in the Yocto Project Development Tasks Manual.
                        For more information on BSP layers, see the
                        "<link linkend='bsp-layers'>BSP Layers</link>"
                        section.
                        <note><title>Notes</title>
                            <para>Five BSPs exist that are part of the Yocto
                            Project release:
                            <filename>beaglebone</filename> (ARM),
                            <filename>mpc8315e</filename> (PowerPC),
                            and <filename>edgerouter</filename> (MIPS).
                            The recipes and configurations for these five BSPs
                            are located and dispersed within the
                            <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.
                            </para>

                            <para>Three core Intel BSPs exist as part of the Yocto
                            Project release in the
                            <filename>meta-intel</filename> layer:
                            <itemizedlist>
                                <listitem><para>
                                    <filename>intel-core2-32</filename>,
                                    which is a BSP optimized for the Core2 family of CPUs
                                    as well as all CPUs prior to the Silvermont core.
                                    </para></listitem>
                                <listitem><para>
                                    <filename>intel-corei7-64</filename>,
                                    which is a BSP optimized for Nehalem and later
                                    Core and Xeon CPUs as well as Silvermont and later
                                    Atom CPUs, such as the Baytrail SoCs.
                                    </para></listitem>
                                <listitem><para>
                                    <filename>intel-quark</filename>,
                                    which is a BSP optimized for the Intel Galileo
                                    gen1 &amp; gen2 development boards.
                                    </para></listitem>
                            </itemizedlist></para>
                        </note></para>

                        <para>When you set up a layer for a new BSP, you should
                        follow a standard layout.
                        This layout is described in the
                        "<link linkend='bsp-filelayout'>Example Filesystem Layout</link>"
                        section.
                        In the standard layout, you will notice a suggested
                        structure for recipes and configuration information.
                        You can see the standard layout for a BSP by examining
                        any supported BSP found in the
                        <filename>meta-intel</filename> layer inside the Source
                        Directory.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Make Configuration Changes to Your New BSP
                        Layer:</emphasis>
                        The standard BSP layer structure organizes the files
                        you need to edit in <filename>conf</filename> and
                        several <filename>recipes-*</filename>
                        directories within the BSP layer.
                        Configuration changes identify where your new layer
                        is on the local system and identify which kernel you
                        are going to use.
                        When you run the <filename>yocto-bsp</filename> script,
                        you are able to interactively configure many things for
                        the BSP (e.g. keyboard, touchscreen, and so forth).
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Make Recipe Changes to Your New BSP
                        Layer:</emphasis>
                        Recipe changes include altering recipes
                        (<filename>.bb</filename> files), removing recipes you
                        do not use, and adding new recipes or append files
                        (<filename>.bbappend</filename>) that you need to
                        support your hardware.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Prepare for the Build:</emphasis>
                        Once you have made all the changes to your BSP layer,
                        there remains a few things you need to do for the
                        OpenEmbedded build system in order for it to create
                        your image.
                        You need to get the build environment ready by
                        sourcing an environment setup script
                        (i.e. <filename>oe-init-build-env</filename>)
                        and you need to be sure two key configuration
                        files are configured appropriately: the
                        <filename>conf/local.conf</filename> and the
                        <filename>conf/bblayers.conf</filename> file.
                        You must make the OpenEmbedded build system aware
                        of your new layer.
                        See the
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#enabling-your-layer'>Enabling Your Layer</ulink>"
                        section in the Yocto Project Development Tasks Manual
                        for information on how to let the build system
                        know about your new layer.</para>

                        <para>The entire process for building an image is
                        overviewed in the section
                        "<ulink url='&YOCTO_DOCS_QS_URL;#qs-building-images'>Building Images</ulink>" section
                        of the Yocto Project Quick Start.
                        You might want to reference this information.
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Build the Image:</emphasis>
                        The OpenEmbedded build system uses the BitBake tool
                        to build images based on the type of image you want to
                        create.
                        You can find more information about BitBake in the
                        <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
                        </para>

                        <para>The build process supports several types of
                        images to satisfy different needs.
                        See the
                        "<ulink url='&YOCTO_DOCS_REF_URL;#ref-images'>Images</ulink>"
                        chapter in the Yocto Project Reference Manual for
                        information on supported images.
                        </para></listitem>
                </orderedlist>
            </para>
        </section>

        <section id='requirements-and-recommendations-for-released-bsps'>
            <title>Requirements and Recommendations for Released BSPs</title>

            <para>
                Certain requirements exist for a released BSP to be considered
                compliant with the Yocto Project.
                Additionally, recommendations also exist.
                This section describes the requirements and recommendations for
                released BSPs.
            </para>

            <section id='released-bsp-requirements'>
                <title>Released BSP Requirements</title>

                <para>
                    Before looking at BSP requirements, you should consider the following:
                    <itemizedlist>
                        <listitem><para>The requirements here assume the BSP layer is a well-formed, "legal"
                            layer that can be added to the Yocto Project.
                            For guidelines on creating a layer that meets these base requirements, see the
                            "<link linkend='bsp-layers'>BSP Layers</link>" and the
                            "<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding
                            and Creating Layers"</ulink> in the Yocto Project Development Tasks Manual.
                            </para></listitem>
                        <listitem><para>The requirements in this section apply regardless of how you
                            package a BSP.
                            You should consult the packaging and distribution guidelines for your
                            specific release process.
                            For an example of packaging and distribution requirements, see the
                            "<ulink url='https://wiki.yoctoproject.org/wiki/Third_Party_BSP_Release_Process'>Third Party BSP Release Process</ulink>"
                            wiki page.
                            </para></listitem>
                        <listitem><para>The requirements for the BSP as it is made available to a developer
                            are completely independent of the released form of the BSP.
                            For example, the BSP Metadata can be contained within a Git repository
                            and could have a directory structure completely different from what appears
                            in the officially released BSP layer.
                            </para></listitem>
                        <listitem><para>It is not required that specific packages or package
                            modifications exist in the BSP layer, beyond the requirements for general
                            compliance with the Yocto Project.
                            For example, no requirement exists dictating that a specific kernel or
                            kernel version be used in a given BSP.
                            </para></listitem>
                    </itemizedlist>
                </para>

                <para>
                    Following are the requirements for a released BSP that conform to the
                    Yocto Project:
                    <itemizedlist>
                        <listitem><para><emphasis>Layer Name:</emphasis>
                            The BSP must have a layer name that follows the Yocto
                            Project standards.
                            For information on BSP layer names, see the
                            "<link linkend='bsp-layers'>BSP Layers</link>" section.
                            </para></listitem>
                        <listitem><para><emphasis>File System Layout:</emphasis>
                            When possible, use the same directory names in your
                            BSP layer as listed in the <filename>recipes.txt</filename> file.
                            In particular, you should place recipes
                            (<filename>.bb</filename> files) and recipe
                            modifications (<filename>.bbappend</filename> files) into
                            <filename>recipes-*</filename> subdirectories by functional area
                            as outlined in <filename>recipes.txt</filename>.
                            If you cannot find a category in <filename>recipes.txt</filename>
                            to fit a particular recipe, you can make up your own
                            <filename>recipes-*</filename> subdirectory.
                            You can find <filename>recipes.txt</filename> in the
                            <filename>meta</filename> directory of the
                            <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>,
                            or in the OpenEmbedded Core Layer
                            (<filename>openembedded-core</filename>) found at
                            <ulink url='http://git.openembedded.org/openembedded-core/tree/meta'></ulink>.
                            </para>
                            <para>Within any particular <filename>recipes-*</filename> category, the layout
                            should match what is found in the OpenEmbedded Core
                            Git repository (<filename>openembedded-core</filename>)
                            or the Source Directory (<filename>poky</filename>).
                            In other words, make sure you place related files in appropriately
                            related <filename>recipes-*</filename> subdirectories specific to the
                            recipe's function, or within a subdirectory containing a set of closely-related
                            recipes.
                            The recipes themselves should follow the general guidelines
                            for recipes used in the Yocto Project found in the
                            "<ulink url='http://openembedded.org/wiki/Styleguide'>OpenEmbedded Style Guide</ulink>".
                            </para></listitem>
                        <listitem><para><emphasis>License File:</emphasis>
                            You must include a license file in the
                            <filename>meta-<replaceable>bsp_name</replaceable></filename> directory.
                            This license covers the BSP Metadata as a whole.
                            You must specify which license to use since there is no
                            default license if one is not specified.
                            See the
                            <ulink url='&YOCTO_GIT_URL;/cgit.cgi/meta-raspberrypi/tree/COPYING.MIT'><filename>COPYING.MIT</filename></ulink>
                            file for the Raspberry Pi BSP in the
                            <filename>meta-raspberrypi</filename> BSP layer as an example.
                            </para></listitem>
                        <listitem><para><emphasis>README File:</emphasis>
                            You must include a <filename>README</filename> file in the
                            <filename>meta-<replaceable>bsp_name</replaceable></filename> directory.
                            See the
                            <ulink url='&YOCTO_GIT_URL;/cgit.cgi/meta-raspberrypi/tree/README'><filename>README</filename></ulink>
                            file for the Raspberry Pi BSP in the <filename>meta-raspberrypi</filename> BSP layer
                            as an example.</para>
                            <para>At a minimum, the <filename>README</filename> file should
                            contain the following:
                            <itemizedlist>
                                <listitem><para>A brief description about the hardware the BSP
                                    targets.</para></listitem>
                                <listitem><para>A list of all the dependencies
                                    on which a BSP layer depends.
                                    These dependencies are typically a list of required layers needed
                                    to build the BSP.
                                    However, the dependencies should also contain information regarding
                                    any other dependencies the BSP might have.</para></listitem>
                                <listitem><para>Any required special licensing information.
                                    For example, this information includes information on
                                    special variables needed to satisfy a EULA,
                                    or instructions on information needed to build or distribute
                                    binaries built from the BSP Metadata.</para></listitem>
                                <listitem><para>The name and contact information for the
                                    BSP layer maintainer.
                                    This is the person to whom patches and questions should
                                    be sent.
                                    For information on how to find the right person, see the
                                    "<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>Submitting a Change to the Yocto Project</ulink>"
                                    section in the Yocto Project Development Tasks Manual.
                                    </para></listitem>
                                <listitem><para>Instructions on how to build the BSP using the BSP
                                    layer.</para></listitem>
                                <listitem><para>Instructions on how to boot the BSP build from
                                    the BSP layer.</para></listitem>
                                <listitem><para>Instructions on how to boot the binary images
                                    contained in the <filename>binary</filename> directory,
                                    if present.</para></listitem>
                                <listitem><para>Information on any known bugs or issues that users
                                    should know about when either building or booting the BSP
                                    binaries.</para></listitem>
                            </itemizedlist></para></listitem>
                        <listitem><para><emphasis>README.sources File:</emphasis>
                            You must include a <filename>README.sources</filename> in the
                            <filename>meta-<replaceable>bsp_name</replaceable></filename> directory.
                            This file specifies exactly where you can find the sources used to
                            generate the binary images contained in the
                            <filename>binary</filename> directory, if present.
                            </para></listitem>
                        <listitem><para><emphasis>Layer Configuration File:</emphasis>
                            You must include a <filename>conf/layer.conf</filename> in the
                            <filename>meta-<replaceable>bsp_name</replaceable></filename> directory.
                            This file identifies the <filename>meta-<replaceable>bsp_name</replaceable></filename>
                            BSP layer as a layer to the build system.</para></listitem>
                        <listitem><para><emphasis>Machine Configuration File:</emphasis>
                            You must include one or more
                            <filename>conf/machine/<replaceable>bsp_name</replaceable>.conf</filename>
                            files in the <filename>meta-<replaceable>bsp_name</replaceable></filename> directory.
                            These configuration files define machine targets that can be built
                            using the BSP layer.
                            Multiple machine configuration files define variations of machine
                            configurations that are supported by the BSP.
                            If a BSP supports multiple machine variations, you need to
                            adequately describe each variation in the BSP
                            <filename>README</filename> file.
                            Do not use multiple machine configuration files to describe disparate
                            hardware.
                            If you do have very different targets, you should create separate
                            BSP layers for each target.
                            <note>It is completely possible for a developer to structure the
                            working repository as a conglomeration of unrelated BSP
                            files, and to possibly generate BSPs targeted for release
                            from that directory using scripts or some other mechanism
                            (e.g. <filename>meta-yocto-bsp</filename> layer).
                            Such considerations are outside the scope of this document.</note>
                            </para></listitem>
                    </itemizedlist>
                </para>
            </section>

            <section id='released-bsp-recommendations'>
                <title>Released BSP Recommendations</title>

                <para>
                    Following are recommendations for a released BSP that conforms to the
                    Yocto Project:
                    <itemizedlist>
                        <listitem><para><emphasis>Bootable Images:</emphasis>
                            BSP releases
                            can contain one or more bootable images.
                            Including bootable images allows users to easily try out the BSP
                            on their own hardware.</para>
                            <para>In some cases, it might not be convenient to include a
                            bootable image.
                            In this case, you might want to make two versions of the
                            BSP available: one that contains binary images, and one
                            that does not.
                            The version that does not contain bootable images avoids
                            unnecessary download times for users not interested in the images.
                            </para>
                            <para>If you need to distribute a BSP and include bootable images or build kernel and
                            filesystems meant to allow users to boot the BSP for evaluation
                            purposes, you should put the images and artifacts within a
                            <filename>binary/</filename> subdirectory located in the
                            <filename>meta-<replaceable>bsp_name</replaceable></filename> directory.
                            <note>If you do include a bootable image as part of the BSP and the image
                            was built by software covered by the GPL or other open source licenses,
                            it is your responsibility to understand
                            and meet all licensing requirements, which could include distribution
                            of source files.</note></para></listitem>
                        <listitem><para><emphasis>Use a Yocto Linux Kernel:</emphasis>
                            Kernel recipes in the BSP should be based on a Yocto Linux kernel.
                            Basing your recipes on these kernels reduces the costs for maintaining
                            the BSP and increases its scalability.
                            See the <filename>Yocto Linux Kernel</filename> category in the
                            <ulink url='&YOCTO_GIT_URL;/cgit.cgi'>Source Repositories</ulink>
                            for these kernels.</para></listitem>
                    </itemizedlist>
                </para>
            </section>
        </section>

        <section id='customizing-a-recipe-for-a-bsp'>
            <title>Customizing a Recipe for a BSP</title>

            <para>
               If you plan on customizing a recipe for a particular BSP, you need to do the
               following:
               <itemizedlist>
                   <listitem><para>Create a <filename>.bbappend</filename>
                       file for the modified recipe.
                       For information on using append files, see the
                       "<ulink url='&YOCTO_DOCS_DEV_URL;#using-bbappend-files'>Using .bbappend Files in Your Layer</ulink>"
                       section in the Yocto Project Development Tasks Manual.
                       </para></listitem>
                   <listitem><para>
                       Ensure your directory structure in the BSP layer
                       that supports your machine is such that it can be found
                       by the build system.
                       See the example later in this section for more information.
                       </para></listitem>
                   <listitem><para>
                       Put the append file in a directory whose name matches
                       the machine's name and is located in an appropriate
                       sub-directory inside the BSP layer (i.e.
                       <filename>recipes-bsp</filename>, <filename>recipes-graphics</filename>,
                       <filename>recipes-core</filename>, and so forth).
                       </para></listitem>
                   <listitem><para>Place the BSP-specific files in the proper directory
                       inside the BSP layer.
                       How expansive the layer is affects where you must place these files.
                       For example, if your layer supports several different machine types,
                       you need to be sure your layer's directory structure includes hierarchy
                       that separates the files out according to machine.
                       If your layer does not support multiple machines, the layer would not
                       have that additional hierarchy and the files would obviously not be
                       able to reside in a machine-specific directory.
                       </para></listitem>
               </itemizedlist>
           </para>

           <para>
               Following is a specific example to help you better understand the process.
               Consider an example that customizes a recipe by adding
               a BSP-specific configuration file named <filename>interfaces</filename> to the
               <filename>init-ifupdown_1.0.bb</filename> recipe for machine "xyz" where the
               BSP layer also supports several other machines.
               Do the following:
               <orderedlist>
                   <listitem><para>Edit the <filename>init-ifupdown_1.0.bbappend</filename> file so that it
                       contains the following:
                       <literallayout class='monospaced'>
     FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
                       </literallayout>
                       The append file needs to be in the
                       <filename>meta-xyz/recipes-core/init-ifupdown</filename> directory.
                       </para></listitem>
                   <listitem><para>Create and place the new <filename>interfaces</filename>
                       configuration file in the BSP's layer here:
                       <literallayout class='monospaced'>
     meta-xyz/recipes-core/init-ifupdown/files/xyz-machine-one/interfaces
                       </literallayout>
                       <note>
                           If the <filename>meta-xyz</filename> layer did not support
                           multiple machines, you would place the
                           <filename>interfaces</filename> configuration file in the
                           layer here:
                           <literallayout class='monospaced'>
     meta-xyz/recipes-core/init-ifupdown/files/interfaces
                           </literallayout>
                       </note>
                       The
                       <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
                       variable in the append files extends the search path
                       the build system uses to find files during the build.
                       Consequently, for this example you need to have the
                       <filename>files</filename> directory in the same location
                       as your append file.</para></listitem>
               </orderedlist>
            </para>
        </section>

        <section id='bsp-licensing-considerations'>
            <title>BSP Licensing Considerations</title>

            <para>
                In some cases, a BSP contains separately licensed Intellectual Property (IP)
                for a component or components.
                For these cases, you are required to accept the terms of a commercial or other
                type of license that requires some kind of explicit End User License Agreement (EULA).
                Once the license is accepted, the OpenEmbedded build system can then build and
                include the corresponding component in the final BSP image.
                If the BSP is available as a pre-built image, you can download the image after
                agreeing to the license or EULA.
            </para>

            <para>
                You could find that some separately licensed components that are essential
                for normal operation of the system might not have an unencumbered (or free)
                substitute.
                Without these essential components, the system would be non-functional.
                Then again, you might find that other licensed components that are simply
                'good-to-have' or purely elective do have an unencumbered, free replacement
                component that you can use rather than agreeing to the separately licensed component.
                Even for components essential to the system, you might find an unencumbered component
                that is not identical but will work as a less-capable version of the
                licensed version in the BSP recipe.
            </para>

            <para>
                For cases where you can substitute a free component and still
                maintain the system's functionality, the "Downloads" page from the
                <ulink url='&YOCTO_HOME_URL;'>Yocto Project website's</ulink>
                makes available de-featured BSPs
                that are completely free of any IP encumbrances.
                For these cases, you can use the substitution directly and
                without any further licensing requirements.
                If present, these fully de-featured BSPs are named appropriately
                different as compared to the names of the respective
                encumbered BSPs.
                If available, these substitutions are your
                simplest and most preferred options.
                Use of these substitutions of course assumes the resulting functionality meets
                system requirements.
            </para>

            <para>
                If however, a non-encumbered version is unavailable or
                it provides unsuitable functionality or quality, you can use an encumbered
                version.
            </para>

            <para>
                A couple different methods exist within the OpenEmbedded build system to
                satisfy the licensing requirements for an encumbered BSP.
                The following list describes them in order of preference:
	        <orderedlist>
                    <listitem><para><emphasis>Use the
                        <ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE_FLAGS'><filename>LICENSE_FLAGS</filename></ulink>
                        variable to define the recipes that have commercial or other
                        types of specially-licensed packages:</emphasis>
                        For each of those recipes, you can
                        specify a matching license string in a
                        <filename>local.conf</filename> variable named
                        <ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE_FLAGS_WHITELIST'><filename>LICENSE_FLAGS_WHITELIST</filename></ulink>.
                        Specifying the matching license string signifies that you agree to the license.
                        Thus, the build system can build the corresponding recipe and include
                        the component in the image.
                        See the
                        "<ulink url='&YOCTO_DOCS_REF_URL;#enabling-commercially-licensed-recipes'>Enabling
                        Commercially Licensed Recipes</ulink>" section in the Yocto Project Reference
                        Manual for details on how to use these variables.</para>
                        <para>If you build as you normally would, without
		        specifying any recipes in the
		        <filename>LICENSE_FLAGS_WHITELIST</filename>, the build stops and
		        provides you with the list of recipes that you have
		        tried to include in the image that need entries in
		        the <filename>LICENSE_FLAGS_WHITELIST</filename>.
		        Once you enter the appropriate license flags into the whitelist,
		        restart the build to continue where it left off.
		        During the build, the prompt will not appear again
		        since you have satisfied the requirement.</para>
                        <para>Once the appropriate license flags are on the white list
		        in the <filename>LICENSE_FLAGS_WHITELIST</filename> variable, you
		        can build the encumbered image with no change at all
		        to the normal build process.</para></listitem>
                    <listitem><para><emphasis>Get a pre-built version of the BSP:</emphasis>
                        You can get this type of BSP by visiting the
                        "Downloads" page of the
                        <ulink url='&YOCTO_HOME_URL;'>Yocto Project website</ulink>.
                        You can download BSP tarballs that contain proprietary components
                        after agreeing to the licensing
                        requirements of each of the individually encumbered
                        packages as part of the download process.
                        Obtaining the BSP this way allows you to access an encumbered
                        image immediately after agreeing to the
                        click-through license agreements presented by the
                        website.
                        Note that if you want to build the image
                        yourself using the recipes contained within the BSP
                        tarball, you will still need to create an
                        appropriate <filename>LICENSE_FLAGS_WHITELIST</filename> to match the
                        encumbered recipes in the BSP.</para></listitem>
	        </orderedlist>
            </para>

            <note>
                Pre-compiled images are bundled with
                a time-limited kernel that runs for a
                predetermined amount of time (10 days) before it forces
                the system to reboot.
                This limitation is meant to discourage direct redistribution
                of the image.
                You must eventually rebuild the image if you want to remove this restriction.
            </note>
        </section>

        <section id='using-the-yocto-projects-bsp-tools'>
            <title>Using the Yocto Project's BSP Tools</title>

            <para>
                The Yocto Project includes a couple of tools that enable
                you to create a <link linkend='bsp-layers'>BSP layer</link>
                from scratch and do basic configuration and maintenance
                of the kernel without ever looking at a Metadata file.
                These tools are <filename>yocto-bsp</filename> and <filename>yocto-kernel</filename>,
                respectively.
	    </para>

            <para>
                The following sections describe the common location and help features as well
                as provide details for the
                <filename>yocto-bsp</filename> and <filename>yocto-kernel</filename> tools.
            </para>

            <section id='common-features'>
                <title>Common Features</title>

                <para>
                    Designed to have a  command interface somewhat like
                    <ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink>, each
                    tool is structured as a set of sub-commands under a
                    top-level command.
                    The top-level command (<filename>yocto-bsp</filename>
                    or <filename>yocto-kernel</filename>) itself does
                    nothing but invoke or provide help on the sub-commands
                    it supports.
                </para>

                <para>
                    Both tools reside in the <filename>scripts/</filename> subdirectory
                    of the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.
                    Consequently, to use the scripts, you must <filename>source</filename> the
                    environment just as you would when invoking a build:
                    <literallayout class='monospaced'>
     $ source oe-init-build-env <replaceable>build_dir</replaceable>
                    </literallayout>
                </para>

                <para>
                    The most immediately useful function is to get help on both tools.
                    The built-in help system makes it easy to drill down at
                    any time and view the syntax required for any specific command.
                    Simply enter the name of the command with the <filename>help</filename>
                    switch:
                    <literallayout class='monospaced'>
     $ yocto-bsp help
     Usage:

      Create a customized Yocto BSP layer.

      usage: yocto-bsp [--version] [--help] COMMAND [ARGS]

      Current 'yocto-bsp' commands are:
         create            Create a new Yocto BSP
         list              List available values for options and BSP properties

      See 'yocto-bsp help COMMAND' for more information on a specific command.


     Options:
       --version    show program's version number and exit
       -h, --help   show this help message and exit
       -D, --debug  output debug information
                    </literallayout>
                </para>

                <para>
                    Similarly, entering just the name of a sub-command shows the detailed usage
                    for that sub-command:
                    <literallayout class='monospaced'>
     $ yocto-bsp create
     ERROR:root:Wrong number of arguments, exiting

     Usage:

      Create a new Yocto BSP

      usage: yocto-bsp create &lt;bsp-name&gt; &lt;karch&gt; [-o &lt;DIRNAME&gt; | --outdir &lt;DIRNAME&gt;]
            [-i &lt;JSON PROPERTY FILE&gt; | --infile &lt;JSON PROPERTY_FILE&gt;]

      This command creates a Yocto BSP based on the specified parameters.
      The new BSP will be a new Yocto BSP layer contained by default within
      the top-level directory specified as 'meta-bsp-name'.  The -o option
      can be used to place the BSP layer in a directory with a different
      name and location.

      The value of the 'karch' parameter determines the set of files that
      will be generated for the BSP, along with the specific set of
      'properties' that will be used to fill out the BSP-specific portions
      of the BSP.  The possible values for the 'karch' parameter can be
      listed via 'yocto-bsp list karch'.

      ...
                    </literallayout>
                </para>

                <para>
                    For any sub-command, you can use the word "help" option just before the
                    sub-command to get more extensive documentation:
                    <literallayout class='monospaced'>
     $ yocto-bsp help create

     NAME
         yocto-bsp create - Create a new Yocto BSP

     SYNOPSIS
         yocto-bsp create &lt;bsp-name> &lt;karch&gt; [-o &lt;DIRNAME&gt; | --outdir &lt;DIRNAME&gt;]
             [-i &lt;JSON PROPERTY FILE&gt; | --infile &lt;JSON PROPERTY_FILE&gt;]

     DESCRIPTION
         This command creates a Yocto BSP based on the specified
         parameters.  The new BSP will be a new Yocto BSP layer contained
         by default within the top-level directory specified as
         'meta-bsp-name'.  The -o option can be used to place the BSP layer
         in a directory with a different name and location.

         ...
                    </literallayout>
                </para>

                <para>
                    Now that you know where these two commands reside and how to access information
                    on them, you should find it relatively straightforward to discover the commands
                    necessary to create a BSP and perform basic kernel maintenance on that BSP using
                    the tools.
                    <note>
                        You can also use the <filename>bitbake-layers</filename> script to create
                        a "generic" layer.
                        For information on using this script to create a layer, see the
                        "<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-bitbake-layers-script'>Creating a General Layer Using the <filename>bitbake-layers</filename> Script</ulink>"
                        section in the Yocto Project Development Tasks Manual.
                    </note>
                </para>

                <para>
                    The next sections provide a concrete starting point to expand on a few points that
                    might not be immediately obvious or that could use further explanation.
                </para>
            </section>


            <section id='creating-a-new-bsp-layer-using-the-yocto-bsp-script'>
                <title>Creating a new BSP Layer Using the yocto-bsp Script</title>

                <para>
                    The <filename>yocto-bsp</filename> script creates a new
                    <link linkend='bsp-layers'>BSP layer</link> for any architecture supported
                    by the Yocto Project, as well as QEMU versions of the same.
                    The default mode of the script's operation is to prompt you for information needed
                    to generate the BSP layer.
                </para>

                <para>
                    For the current set of BSPs, the script prompts you for various important
                    parameters such as:
                    <itemizedlist>
                        <listitem><para>The kernel to use</para></listitem>
                        <listitem><para>The branch of that kernel to use (or re-use)</para></listitem>
                        <listitem><para>Whether or not to use X, and if so, which drivers to use</para></listitem>
                        <listitem><para>Whether to turn on SMP</para></listitem>
                        <listitem><para>Whether the BSP has a keyboard</para></listitem>
                        <listitem><para>Whether the BSP has a touchscreen</para></listitem>
                        <listitem><para>Remaining configurable items associated with the BSP</para></listitem>
                    </itemizedlist>
                </para>

                <para>
                    You use the <filename>yocto-bsp create</filename> sub-command to create
                    a new BSP layer.
                    This command requires you to specify a particular kernel architecture
                    (<filename>karch</filename>) on which to base the BSP.
                    Assuming you have sourced the environment, you can use the
                    <filename>yocto-bsp list karch</filename> sub-command to list the
                    architectures available for BSP creation as follows:
                    <literallayout class='monospaced'>
     $ yocto-bsp list karch
     Architectures available:
         powerpc
         x86_64
         i386
         arm
         qemu
         mips
         mips64
                    </literallayout>
                </para>

                <para>
                    The remainder of this section presents an example that uses
                    <filename>myarm</filename> as the machine name and <filename>qemu</filename>
                    as the machine architecture.
                    Of the available architectures, <filename>qemu</filename> is the only architecture
                    that causes the script to prompt you further for an actual architecture.
                    In every other way, this architecture is representative of how creating a BSP for
                    an actual machine would work.
                    The reason the example uses this architecture is because it is an emulated architecture
                    and can easily be followed without requiring actual hardware.
                </para>

                <para>
                    As the <filename>yocto-bsp create</filename> command runs, default values for
                    the prompts appear in brackets.
                    Pressing enter without supplying anything on the command line or pressing enter
                    with an invalid response causes the script to accept the default value.
                    Once the script completes, the new <filename>meta-myarm</filename> BSP layer
                    is created in the current working directory.
                    This example assumes you have sourced the
                    <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
                    setup script.
                </para>

                <para>
                    Following is the complete example:
                    <literallayout class='monospaced'>
     $ yocto-bsp create myarm qemu
     Checking basic git connectivity...
     Done.

     Which qemu architecture would you like to use? [default: i386]
	     1) i386    (32-bit)
	     2) x86_64  (64-bit)
	     3) ARM     (32-bit)
	     4) PowerPC (32-bit)
	     5) MIPS    (32-bit)
	     6) MIPS64  (64-bit)
     3
     Would you like to use the default (4.8) kernel? (y/n) [default: y]
     Do you need a new machine branch for this BSP (the alternative is to re-use an existing branch)? [y/n] [default: y]
     Getting branches from remote repo git://git.yoctoproject.org/linux-yocto-4.8.git...
     Please choose a machine branch to base this BSP on: [default: standard/base]
	     1) standard/arm-versatile-926ejs
	     2) standard/base
	     3) standard/beaglebone
	     4) standard/edgerouter
	     5) standard/fsl-mpc8315e-rdb
	     6) standard/mti-malta32
	     7) standard/mti-malta64
	     8) standard/qemuarm64
	     9) standard/qemuppc
     1
     Would you like SMP support? (y/n) [default: y]
     Does your BSP have a touchscreen? (y/n) [default: n]
     Does your BSP have a keyboard? (y/n) [default: y]

     New qemu BSP created in meta-myarm
                    </literallayout>
                    Take a closer look at the example now:
                    <orderedlist>
                        <listitem><para>For the QEMU architecture,
                            the script first prompts you for which emulated architecture to use.
                            In the example, we use the ARM architecture.
                            </para></listitem>
                        <listitem><para>The script then prompts you for the kernel.
                            The default 4.8 kernel is acceptable.
                            So, the example accepts the default.
                            If you enter 'n', the script prompts you to further enter the kernel
                            you do want to use.</para></listitem>
                        <listitem><para>Next, the script asks whether you would like to have a new
                            branch created especially for your BSP in the local
                            Linux Yocto Kernel Git repository .
                            If not, then the script re-uses an existing branch.</para>
                            <para>In this example, the default (or "yes") is accepted.
                            Thus, a new branch is created for the BSP rather than using a common, shared
                            branch.
                            The new branch is the branch committed to for any patches you might later add.
                            The reason a new branch is the default is that typically
                            new BSPs do require BSP-specific patches.
                            The tool thus assumes that most of time a new branch is required.
                            </para></listitem>
                        <listitem><para>Regardless of which choice you make in the previous step,
                            you are now given the opportunity to select a particular machine branch on
                            which to base your new BSP-specific machine branch
                            (or to re-use if you had elected to not create a new branch).
                            Because this example is generating an ARM-based BSP, the example
                            uses <filename>#1</filename> at the prompt, which selects the ARM-versatile branch.
                            </para></listitem>
                        <listitem><para>The remainder of the prompts are routine.
                            Defaults are accepted for each.</para></listitem>
                        <listitem><para>By default, the script creates the new BSP Layer in the
                            current working directory of the
                            <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>,
                            (i.e. <filename>poky/build</filename>).
                            </para></listitem>
                    </orderedlist>
                </para>

                <para>
                    Once the BSP Layer is created, you must add it to your
                    <filename>bblayers.conf</filename> file.
                    Here is an example:
                    <literallayout class='monospaced'>
     BBLAYERS = ? " \
        /usr/local/src/yocto/meta \
        /usr/local/src/yocto/meta-poky \
        /usr/local/src/yocto/meta-yocto-bsp \
        /usr/local/src/yocto/meta-myarm \
        "
                    </literallayout>
                    Adding the layer to this file allows the build system to build the BSP and
                    the <filename>yocto-kernel</filename> tool to be able to find the layer and
                    other Metadata it needs on which to operate.
                </para>
            </section>

            <section id='managing-kernel-patches-and-config-items-with-yocto-kernel'>
                <title>Managing Kernel Patches and Config Items with yocto-kernel</title>

                <para>
                    Assuming you have created a <link linkend='bsp-layers'>BSP Layer</link> using
                    <link linkend='creating-a-new-bsp-layer-using-the-yocto-bsp-script'>
                    <filename>yocto-bsp</filename></link> and you added it to your
                    <ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
                    variable in the <filename>bblayers.conf</filename> file, you can now use
                    the <filename>yocto-kernel</filename> script to add patches and configuration
                    items to the BSP's kernel.
                </para>

                <para>
                    The <filename>yocto-kernel</filename> script allows you to add, remove, and list patches
                    and kernel config settings to a BSP's kernel
                    <filename>.bbappend</filename> file.
                    All you need to do is use the appropriate sub-command.
                    Recall that the easiest way to see exactly what sub-commands are available
                    is to use the <filename>yocto-kernel</filename> built-in help as follows:
                    <literallayout class='monospaced'>
     $ yocto-kernel --help
     Usage:

      Modify and list Yocto BSP kernel config items and patches.

      usage: yocto-kernel [--version] [--help] COMMAND [ARGS]

      Current 'yocto-kernel' commands are:
        config list       List the modifiable set of bare kernel config options for a BSP
        config add        Add or modify bare kernel config options for a BSP
        config rm         Remove bare kernel config options from a BSP
        patch list        List the patches associated with a BSP
        patch add         Patch the Yocto kernel for a BSP
        patch rm          Remove patches from a BSP
        feature list      List the features used by a BSP
        feature add       Have a BSP use a feature
        feature rm        Have a BSP stop using a feature
        features list     List the features available to BSPs
        feature describe  Describe a particular feature
        feature create    Create a new BSP-local feature
        feature destroy   Remove a BSP-local feature

      See 'yocto-kernel help COMMAND' for more information on a specific command.



     Options:
       --version    show program's version number and exit
       -h, --help   show this help message and exit
       -D, --debug  output debug information
                    </literallayout>
                </para>

                <para>
                    The <filename>yocto-kernel patch add</filename> sub-command allows you to add a
                    patch to a BSP.
                    The following example adds two patches to the <filename>myarm</filename> BSP:
                    <literallayout class='monospaced'>
     $ yocto-kernel patch add myarm ~/test.patch
     Added patches:
       test.patch

     $ yocto-kernel patch add myarm ~/yocto-testmod.patch
     Added patches:
       yocto-testmod.patch
                    </literallayout>
                    <note>Although the previous example adds patches one at a time, it is possible
                    to add multiple patches at the same time.</note>
                </para>

                <para>
                    You can verify patches have been added by using the
                    <filename>yocto-kernel patch list</filename> sub-command.
                    Here is an example:
                    <literallayout class='monospaced'>
     $ yocto-kernel patch list myarm
     The current set of machine-specific patches for myarm is:
       1) test.patch
       2) yocto-testmod.patch
                    </literallayout>
                </para>

                <para>
                    You can also use the <filename>yocto-kernel</filename> script to
                    remove a patch using the <filename>yocto-kernel patch rm</filename> sub-command.
                    Here is an example:
                    <literallayout class='monospaced'>
     $ yocto-kernel patch rm myarm
     Specify the patches to remove:
       1) test.patch
       2) yocto-testmod.patch
     1
     Removed patches:
       test.patch
                    </literallayout>
                </para>

                <para>
                    Again, using the <filename>yocto-kernel patch list</filename> sub-command,
                    you can verify that the patch was in fact removed:
                    <literallayout class='monospaced'>
     $ yocto-kernel patch list myarm
     The current set of machine-specific patches for myarm is:
       1) yocto-testmod.patch
                    </literallayout>
                </para>

                <para>
                    In a completely similar way, you can use the <filename>yocto-kernel config add</filename>
                    sub-command to add one or more kernel config item settings to a BSP.
                    The following commands add a couple of config items to the
                    <filename>myarm</filename> BSP:
                    <literallayout class='monospaced'>
     $ yocto-kernel config add myarm CONFIG_MISC_DEVICES=y
     Added item:
       CONFIG_MISC_DEVICES=y

     $ yocto-kernel config add myarm CONFIG_YOCTO_TESTMOD=y
     Added item:
       CONFIG_YOCTO_TESTMOD=y
                    </literallayout>
                    <note>
                        Although the previous example adds config items one at a time, it is possible
                        to add multiple config items at the same time.
                    </note>
                </para>

                <para>
                    You can list the config items now associated with the BSP.
                    Doing so shows you the config items you added as well as others associated
                    with the BSP:
                    <literallayout class='monospaced'>
     $ yocto-kernel config list myarm
     The current set of machine-specific kernel config items for myarm is:
             1) CONFIG_MISC_DEVICES=y
             2) CONFIG_YOCTO_TESTMOD=y
                    </literallayout>
                </para>

                <para>
                    Finally, you can remove one or more config items using the
                    <filename>yocto-kernel config rm</filename> sub-command in a manner
                    completely analogous to <filename>yocto-kernel patch rm</filename>.
                </para>
            </section>
        </section>
</chapter>