1480 lines
78 KiB
XML
1480 lines
78 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='bsp'>
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<title>Board Support Packages (BSP) - Developer's Guide</title>
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<para>
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A Board Support Package (BSP) is a collection of information that
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defines how to support a particular hardware device, set of devices, or
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hardware platform.
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The BSP includes information about the hardware features
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present on the device and kernel configuration information along with any
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additional hardware drivers required.
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The BSP also lists any additional software
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components required in addition to a generic Linux software stack for both
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essential and optional platform features.
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</para>
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<para>
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This guide presents information about BSP Layers, defines a structure for components
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so that BSPs follow a commonly understood layout, discusses how to customize
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a recipe for a BSP, addresses BSP licensing, and provides information that
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shows you how to create and manage a
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<link linkend='bsp-layers'>BSP Layer</link> using two Yocto Project
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<link linkend='using-the-yocto-projects-bsp-tools'>BSP Tools</link>.
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</para>
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<section id='bsp-layers'>
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<title>BSP Layers</title>
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<para>
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The BSP consists of a file structure inside a base directory.
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Collectively, you can think of the base directory and the file structure
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as a BSP Layer.
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Although not a strict requirement, layers in the Yocto Project use the
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following well established naming convention:
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<literallayout class='monospaced'>
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meta-<bsp_name>
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</literallayout>
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The string "meta-" is prepended to the machine or platform name, which is
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"bsp_name" in the above form.
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</para>
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<para>
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The layer's base directory (<filename>meta-<bsp_name></filename>) is the root
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of the BSP Layer.
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This root is what you add to the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-BBLAYERS'><filename>BBLAYERS</filename></ulink>
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variable in the <filename>conf/bblayers.conf</filename> file found in the
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<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
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Adding the root allows the OpenEmbedded build system to recognize the BSP
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definition and from it build an image.
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Here is an example:
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<literallayout class='monospaced'>
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BBLAYERS ?= " \
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/usr/local/src/yocto/meta \
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/usr/local/src/yocto/meta-yocto \
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/usr/local/src/yocto/meta-yocto-bsp \
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/usr/local/src/yocto/meta-mylayer \
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"
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BBLAYERS_NON_REMOVABLE ?= " \
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/usr/local/src/yocto/meta \
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/usr/local/src/yocto/meta-yocto \
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"
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</literallayout>
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</para>
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<para>
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Some BSPs require additional layers on
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top of the BSP's root layer in order to be functional.
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For these cases, you also need to add those layers to the
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<filename>BBLAYERS</filename> variable in order to build the BSP.
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You must also specify in the "Dependencies" section of the BSP's
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<filename>README</filename> file any requirements for additional
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layers and, preferably, any
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build instructions that might be contained elsewhere
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in the <filename>README</filename> file.
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</para>
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<para>
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Some layers function as a layer to hold other BSP layers.
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An example of this type of layer is the <filename>meta-intel</filename> layer.
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The <filename>meta-intel</filename> layer contains over 10 individual BSP layers.
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</para>
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<para>
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For more detailed information on layers, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
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section of the Yocto Project Development Manual.
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</para>
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</section>
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<section id="bsp-filelayout">
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<title>Example Filesystem Layout</title>
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<para>
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Providing a common form allows end-users to understand and become familiar
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with the layout.
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A common format also encourages standardization of software support of hardware.
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</para>
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<para>
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The proposed form does have elements that are specific to the
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OpenEmbedded build system.
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It is intended that this information can be
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used by other build systems besides the OpenEmbedded build system
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and that it will be simple
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to extract information and convert it to other formats if required.
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The OpenEmbedded build system, through its standard layers mechanism, can directly
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accept the format described as a layer.
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The BSP captures all
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the hardware-specific details in one place in a standard format, which is
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useful for any person wishing to use the hardware platform regardless of
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the build system they are using.
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</para>
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<para>
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The BSP specification does not include a build system or other tools -
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it is concerned with the hardware-specific components only.
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At the end-distribution point, you can ship the BSP combined with a build system
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and other tools.
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However, it is important to maintain the distinction that these
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are separate components that happen to be combined in certain end products.
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</para>
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<para>
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Before looking at the common form for the file structure inside a BSP Layer,
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you should be aware that some requirements do exist in order for a BSP to
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be considered compliant with the Yocto Project.
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For that list of requirements, see the
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"<link linkend='released-bsp-requirements'>Released BSP Requirements</link>"
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section.
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</para>
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<para>
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Below is the common form for the file structure inside a BSP Layer.
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While you can use this basic form for the standard, realize that the actual structures
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for specific BSPs could differ.
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<literallayout class='monospaced'>
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meta-<bsp_name>/
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meta-<bsp_name>/<bsp_license_file>
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meta-<bsp_name>/README
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meta-<bsp_name>/README.sources
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meta-<bsp_name>/binary/<bootable_images>
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meta-<bsp_name>/conf/layer.conf
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meta-<bsp_name>/conf/machine/*.conf
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meta-<bsp_name>/recipes-bsp/*
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meta-<bsp_name>/recipes-core/*
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meta-<bsp_name>/recipes-graphics/*
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meta-<bsp_name>/recipes-kernel/linux/linux-yocto_<kernel_rev>.bbappend
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</literallayout>
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</para>
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<para>
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Below is an example of the Crown Bay BSP:
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<literallayout class='monospaced'>
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meta-crownbay/COPYING.MIT
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meta-crownbay/README
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meta-crownbay/README.sources
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meta-crownbay/binary/
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meta-crownbay/conf/
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meta-crownbay/conf/layer.conf
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meta-crownbay/conf/machine/
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meta-crownbay/conf/machine/crownbay.conf
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meta-crownbay/conf/machine/crownbay-noemgd.conf
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meta-crownbay/recipes-bsp/
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meta-crownbay/recipes-bsp/formfactor/
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meta-crownbay/recipes-bsp/formfactor/formfactor_0.0.bbappend
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meta-crownbay/recipes-bsp/formfactor/formfactor/
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meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay/
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meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay/machconfig
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meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay-noemgd/
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meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay-noemgd/machconfig
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meta-crownbay/recipes-graphics/
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meta-crownbay/recipes-graphics/xorg-xserver/
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meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config_0.1.bbappend
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meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/
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meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay/
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meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay/xorg.conf
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meta-crownbay/recipes-kernel/
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meta-crownbay/recipes-kernel/linux/
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meta-crownbay/recipes-kernel/linux/linux-yocto_3.4.bbappend
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meta-crownbay/recipes-kernel/linux/linux-yocto_3.8.bbappend
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meta-crownbay/recipes-kernel/linux/linux-yocto_3.10.bbappend
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meta-crownbay/recipes-kernel/linux/linux-yocto-dev.bbappend
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meta-crownbay/recipes-kernel/linux/linux-yocto-rt_3.4.bbappend
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meta-crownbay/recipes-kernel/linux/linux-yocto-rt_3.8.bbappend
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meta-crownbay/recipes-kernel/linux/linux-yocto-rt_3.10.bbappend
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</literallayout>
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</para>
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<para>
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The following sections describe each part of the proposed BSP format.
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</para>
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<section id="bsp-filelayout-license">
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<title>License Files</title>
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<para>
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You can find these files in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/<bsp_license_file>
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</literallayout>
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</para>
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<para>
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These optional files satisfy licensing requirements for the BSP.
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The type or types of files here can vary depending on the licensing requirements.
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For example, in the Crown Bay BSP all licensing requirements are handled with the
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<filename>COPYING.MIT</filename> file.
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</para>
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<para>
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Licensing files can be MIT, BSD, GPLv*, and so forth.
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These files are recommended for the BSP but are optional and totally up to the BSP developer.
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</para>
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</section>
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<section id="bsp-filelayout-readme">
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<title>README File</title>
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<para>
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You can find this file in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/README
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</literallayout>
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</para>
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<para>
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This file provides information on how to boot the live images that are optionally
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included in the <filename>binary/</filename> directory.
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The <filename>README</filename> file also provides special information needed for
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building the image.
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</para>
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<para>
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At a minimum, the <filename>README</filename> file must
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contain a list of dependencies, such as the names of
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any other layers on which the BSP depends and the name of
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the BSP maintainer with his or her contact information.
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</para>
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</section>
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<section id="bsp-filelayout-readme-sources">
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<title>README.sources File</title>
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<para>
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You can find this file in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/README.sources
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</literallayout>
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</para>
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<para>
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This file provides information on where to locate the BSP source files.
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For example, information provides where to find the sources that comprise
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the images shipped with the BSP.
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Information is also included to help you find the
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<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>
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used to generate the images that ship with the BSP.
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</para>
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</section>
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<section id="bsp-filelayout-binary">
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<title>Pre-built User Binaries</title>
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<para>
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You can find these files in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/binary/<bootable_images>
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</literallayout>
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</para>
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<para>
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This optional area contains useful pre-built kernels and user-space filesystem
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images appropriate to the target system.
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This directory typically contains graphical (e.g. Sato) and minimal live images
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when the BSP tarball has been created and made available in the
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<ulink url='&YOCTO_HOME_URL;'>Yocto Project</ulink> website.
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You can use these kernels and images to get a system running and quickly get started
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on development tasks.
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</para>
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<para>
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The exact types of binaries present are highly hardware-dependent.
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However, a README file should be present in the BSP Layer that explains how to use
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the kernels and images with the target hardware.
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If pre-built binaries are present, source code to meet licensing requirements must also
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exist in some form.
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</para>
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</section>
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<section id='bsp-filelayout-layer'>
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<title>Layer Configuration File</title>
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<para>
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You can find this file in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/conf/layer.conf
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</literallayout>
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</para>
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<para>
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The <filename>conf/layer.conf</filename> file identifies the file structure as a
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layer, identifies the
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contents of the layer, and contains information about how the build
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system should use it.
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Generally, a standard boilerplate file such as the following works.
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In the following example, you would replace "<filename>bsp</filename>" and
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"<filename>_bsp</filename>" with the actual name
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of the BSP (i.e. <filename><bsp_name></filename> from the example template).
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</para>
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<para>
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<literallayout class='monospaced'>
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# We have a conf and classes directory, add to BBPATH
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BBPATH .= ":${LAYERDIR}"
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# We have a recipes directory, add to BBFILES
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BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
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${LAYERDIR}/recipes-*/*/*.bbappend"
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BBFILE_COLLECTIONS += "bsp"
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BBFILE_PATTERN_bsp = "^${LAYERDIR}/"
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BBFILE_PRIORITY_bsp = "6"
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</literallayout>
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</para>
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<para>
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To illustrate the string substitutions, here are the corresponding statements
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from the Crown Bay <filename>conf/layer.conf</filename> file:
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<literallayout class='monospaced'>
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BBFILE_COLLECTIONS += "crownbay"
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BBFILE_PATTERN_crownbay = "^${LAYERDIR}/"
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BBFILE_PRIORITY_crownbay = "6"
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</literallayout>
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</para>
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<para>
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This file simply makes BitBake aware of the recipes and configuration directories.
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The file must exist so that the OpenEmbedded build system can recognize the BSP.
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</para>
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</section>
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<section id="bsp-filelayout-machine">
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<title>Hardware Configuration Options</title>
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<para>
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You can find these files in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/conf/machine/*.conf
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</literallayout>
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</para>
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<para>
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The machine files bind together all the information contained elsewhere
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in the BSP into a format that the build system can understand.
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If the BSP supports multiple machines, multiple machine configuration files
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can be present.
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These filenames correspond to the values to which users have set the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-MACHINE'><filename>MACHINE</filename></ulink> variable.
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</para>
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<para>
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These files define things such as the kernel package to use
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(<ulink url='&YOCTO_DOCS_REF_URL;#var-PREFERRED_PROVIDER'><filename>PREFERRED_PROVIDER</filename></ulink>
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of virtual/kernel), the hardware drivers to
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include in different types of images, any special software components
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that are needed, any bootloader information, and also any special image
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format requirements.
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</para>
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<para>
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Each BSP Layer requires at least one machine file.
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However, you can supply more than one file.
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</para>
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<para>
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This <filename>crownbay.conf</filename> file could also include
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a hardware "tuning" file that is commonly used to
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define the package architecture and specify
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optimization flags, which are carefully chosen to give best
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performance on a given processor.
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</para>
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<para>
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Tuning files are found in the <filename>meta/conf/machine/include</filename>
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directory within the
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<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
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For example, the <filename>ia32-base.inc</filename> file resides in the
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<filename>meta/conf/machine/include</filename> directory.
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</para>
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<para>
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To use an include file, you simply include them in the machine configuration file.
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For example, the Crown Bay BSP <filename>crownbay.conf</filename> has the
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following statements:
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<literallayout class='monospaced'>
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require conf/machine/include/tune-atom.inc
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require conf/machine/include/ia32-base.inc
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require conf/machine/include/meta-intel.inc
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</literallayout>
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</para>
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</section>
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<section id='bsp-filelayout-misc-recipes'>
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<title>Miscellaneous BSP-Specific Recipe Files</title>
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<para>
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You can find these files in the BSP Layer at:
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<literallayout class='monospaced'>
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meta-<bsp_name>/recipes-bsp/*
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</literallayout>
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</para>
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<para>
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This optional directory contains miscellaneous recipe files for the BSP.
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Most notably would be the formfactor files.
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For example, in the Crown Bay BSP there is the
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<filename>formfactor_0.0.bbappend</filename> file, which is an
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append file used to augment the recipe that starts the build.
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Furthermore, there are machine-specific settings used during the
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build that are defined by the <filename>machconfig</filename>.
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In the Crown Bay example, two <filename>machconfig</filename> files
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exist: one that supports the Intel® Embedded Media and Graphics
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Driver (Intel® EMGD) and one that does not:
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<literallayout class='monospaced'>
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meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay/machconfig
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meta-crownbay/recipes-bsp/formfactor/formfactor/crownbay-noemgd/machconfig
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meta-crownbay/recipes-bsp/formfactor/formfactor_0.0.bbappend
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</literallayout>
|
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</para>
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|
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<note><para>
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If a BSP does not have a formfactor entry, defaults are established according to
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the formfactor configuration file that is installed by the main
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formfactor recipe
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<filename>meta/recipes-bsp/formfactor/formfactor_0.0.bb</filename>,
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which is found in the
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<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
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</para></note>
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</section>
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|
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<section id='bsp-filelayout-recipes-graphics'>
|
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<title>Display Support Files</title>
|
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<para>
|
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You can find these files in the BSP Layer at:
|
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<literallayout class='monospaced'>
|
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meta-<bsp_name>/recipes-graphics/*
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</literallayout>
|
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</para>
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<para>
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This optional directory contains recipes for the BSP if it has
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special requirements for graphics support.
|
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All files that are needed for the BSP to support a display are kept here.
|
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For example, the Crown Bay BSP's <filename>xorg.conf</filename> file
|
|
detects the graphics support needed (i.e. the Intel® Embedded Media
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Graphics Driver (EMGD) or the Video Electronics Standards Association
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(VESA) graphics):
|
|
<literallayout class='monospaced'>
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meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config_0.1.bbappend
|
|
meta-crownbay/recipes-graphics/xorg-xserver/xserver-xf86-config/crownbay-noemgd/xorg.conf
|
|
</literallayout>
|
|
</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-<bsp_name>/recipes-kernel/linux/linux-yocto_*.bbappend
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
These files append your 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_DEV_URL;#source-directory'>Source Directory</ulink>
|
|
at <filename>meta/recipes-kernel/linux</filename>.
|
|
You can append your specific changes to the kernel recipe by using a
|
|
similarly named append file, which is located in the BSP Layer (e.g.
|
|
the <filename>meta-<bsp_name>/recipes-kernel/linux</filename> directory).
|
|
</para>
|
|
<para>
|
|
Suppose you are using the <filename>linux-yocto_3.10.bb</filename> recipe to build
|
|
the kernel.
|
|
In other words, you have selected the kernel in your
|
|
<filename><bsp_name>.conf</filename> file by adding these types
|
|
of statements:
|
|
<literallayout class='monospaced'>
|
|
PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
|
|
PREFERRED_VERSION_linux-yocto ?= "3.10%"
|
|
</literallayout>
|
|
<note>
|
|
When the preferred provider is assumed by default, the
|
|
<filename>PREFERRED_PROVIDER</filename> statement does not appear in the
|
|
<filename><bsp_name>.conf</filename> file.
|
|
</note>
|
|
You would use the <filename>linux-yocto_3.10.bbappend</filename> file to append
|
|
specific BSP settings to the kernel, thus configuring the kernel for your particular BSP.
|
|
</para>
|
|
<para>
|
|
As an example, look at the existing Crown Bay BSP.
|
|
The append file used is:
|
|
<literallayout class='monospaced'>
|
|
meta-crownbay/recipes-kernel/linux/linux-yocto_3.10.bbappend
|
|
</literallayout>
|
|
The following listing shows the file.
|
|
Be aware that the actual commit ID strings in this example listing might be different
|
|
than the actual strings in the file from the <filename>meta-intel</filename>
|
|
Git source repository.
|
|
<literallayout class='monospaced'>
|
|
FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
|
|
|
|
COMPATIBLE_MACHINE_crownbay-noemgd = "crownbay-noemgd"
|
|
KMACHINE_crownbay-noemgd = "crownbay"
|
|
KBRANCH_crownbay-noemgd = "standard/crownbay"
|
|
KERNEL_FEATURES_append_crownbay-noemgd = " cfg/vesafb"
|
|
|
|
LINUX_VERSION = "3.10.11"
|
|
|
|
SRCREV_meta_crownbay-noemgd = "285f93bf942e8f6fa678ffc6cc53696ed5400718"
|
|
SRCREV_machine_crownbay-noemgd = "702040ac7c7ec66a29b4d147665ccdd0ff015577"
|
|
</literallayout>
|
|
This append file contains statements used to support the Crown Bay BSP.
|
|
The file defines <filename>crownbay</filename> as the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-COMPATIBLE_MACHINE'><filename>COMPATIBLE_MACHINE</filename></ulink>
|
|
and uses the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KMACHINE'><filename>KMACHINE</filename></ulink> variable to
|
|
ensure the machine name used by the OpenEmbedded build system maps to the
|
|
machine name used by the Linux Yocto kernel.
|
|
The file also uses the optional
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KBRANCH'><filename>KBRANCH</filename></ulink> variable
|
|
to ensure the build process uses the <filename>standard/crownbay</filename>
|
|
kernel branch.
|
|
The
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-KERNEL_FEATURES'><filename>KERNEL_FEATURES</filename></ulink>
|
|
variable enables features specific to the kernel.
|
|
Finally, the append file points to specific commits in the
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink> Git
|
|
repository and the <filename>meta</filename> Git repository branches to identify the
|
|
exact kernel needed to build the Crown Bay BSP.
|
|
</para>
|
|
|
|
<para>
|
|
One thing missing in this particular BSP, which you will typically need when
|
|
developing a BSP, is the kernel configuration file (<filename>.config</filename>) for your BSP.
|
|
When developing a BSP, you probably have a kernel configuration file or a set of kernel
|
|
configuration files that, when taken together, define the kernel configuration for your BSP.
|
|
You can accomplish this definition by putting the configurations in a file or a set of files
|
|
inside a directory located at the same level as your kernel's append file and having the same
|
|
name as the kernel's main recipe file.
|
|
With all these conditions met, simply reference those files in a
|
|
<filename>SRC_URI</filename> statement in the append file.
|
|
</para>
|
|
|
|
<para>
|
|
For example, suppose you had some configuration options in a file called
|
|
<filename>network_configs.cfg</filename>.
|
|
You can place that file inside a directory named <filename>/linux-yocto</filename> and then add
|
|
a <filename>SRC_URI</filename> statement such as the following to the append file.
|
|
When the OpenEmbedded build system builds the kernel, the configuration options are
|
|
picked up and applied.
|
|
<literallayout class='monospaced'>
|
|
SRC_URI += "file://network_configs.cfg"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
To group related configurations into multiple files, you perform a similar procedure.
|
|
Here is an example that groups separate configurations specifically for Ethernet and graphics
|
|
into their own files and adds the configurations
|
|
by using a <filename>SRC_URI</filename> statement like the following in your append file:
|
|
<literallayout class='monospaced'>
|
|
SRC_URI += "file://myconfig.cfg \
|
|
file://eth.cfg \
|
|
file://gfx.cfg"
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
The <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
|
|
variable is in boilerplate form in the
|
|
previous example in order to make it easy to do that.
|
|
This variable must be in your layer or BitBake will not find the patches or
|
|
configurations even if you have them in your <filename>SRC_URI</filename>.
|
|
The <filename>FILESEXTRAPATHS</filename> variable enables the build process to
|
|
find those configuration files.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Other methods exist to accomplish grouping and defining configuration options.
|
|
For example, if you are working with a local clone of the kernel repository,
|
|
you could checkout the kernel's <filename>meta</filename> branch, make your changes,
|
|
and then push the changes to the local bare clone of the kernel.
|
|
The result is that you directly add configuration options to the
|
|
<filename>meta</filename> branch for your BSP.
|
|
The configuration options will likely end up in that location anyway if the BSP gets
|
|
added to the Yocto Project.
|
|
</para>
|
|
|
|
<para>
|
|
In general, however, the Yocto Project maintainers take care of moving the
|
|
<filename>SRC_URI</filename>-specified
|
|
configuration options to the kernel's <filename>meta</filename> branch.
|
|
Not only is it easier for BSP developers to not have to worry about putting those
|
|
configurations in the branch, but having the maintainers do it allows them to apply
|
|
'global' knowledge about the kinds of common configuration options multiple BSPs in
|
|
the tree are typically using.
|
|
This allows for promotion of common configurations into common features.
|
|
</para>
|
|
</note>
|
|
</section>
|
|
</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 Manual.</para></listitem>
|
|
<listitem><para>The requirements in this section apply regardless of how you
|
|
ultimately 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 conforms 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_DEV_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='https://wiki.yoctoproject.org/wiki/Recipe_%26_Patch_Style_Guide'>Yocto Recipe and Patch Style Guide</ulink>".
|
|
</para></listitem>
|
|
<listitem><para><emphasis>License File:</emphasis>
|
|
You must include a license file in the
|
|
<filename>meta-<bsp_name></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-intel/tree/meta-fri2/COPYING.MIT'><filename>COPYING.MIT</filename></ulink>
|
|
file for the Fish River Island 2 BSP in the <filename>meta-fri2</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-<bsp_name></filename> directory.
|
|
See the
|
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi/meta-intel/tree/meta-fri2/README'><filename>README</filename></ulink>
|
|
file for the Fish River Island 2 BSP in the <filename>meta-fri2</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'>How to Submit a Change</ulink>"
|
|
section in the Yocto Project Development 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-<bsp_name></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.
|
|
See the
|
|
<ulink url='&YOCTO_GIT_URL;/cgit.cgi/meta-intel/tree/meta-fri2/README.sources'><filename>README.sources</filename></ulink>
|
|
file for the Fish River Island 2 BSP in the <filename>meta-fri2</filename> BSP layer
|
|
as an example.</para></listitem>
|
|
<listitem><para><emphasis>Layer Configuration File:</emphasis>
|
|
You must include a <filename>conf/layer.conf</filename> in the
|
|
<filename>meta-<bsp_name></filename> directory.
|
|
This file identifies the <filename>meta-<bsp_name></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/<bsp_name>.conf</filename>
|
|
files in the <filename>meta-<bsp_name></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-<bsp_name></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</ulink>"
|
|
section in the Yocto Project Development 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 directory named for
|
|
your machine inside the BSP layer.
|
|
</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".
|
|
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:"
|
|
PRINC := "${@int(PRINC) + 2}"
|
|
</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/interfaces
|
|
</literallayout>
|
|
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 <filename>LICENSE_FLAGS</filename> 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
|
|
<filename>LICENSE_FLAGS_WHITELIST</filename>.
|
|
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_DEV_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_DEV_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 [build_dir]
|
|
</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
|
|
|
|
Usage:
|
|
|
|
Create a new Yocto BSP
|
|
|
|
usage: yocto-bsp create <bsp-name> <karch> [-o <DIRNAME> | --outdir <DIRNAME>]
|
|
[-i <JSON PROPERTY FILE> | --infile <JSON PROPERTY_FILE>]
|
|
|
|
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>
|
|
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 <bsp-name> <karch> [-o <DIRNAME> | --outdir <DIRNAME>]
|
|
[-i <JSON PROPERTY FILE> | --infile <JSON PROPERTY_FILE>]
|
|
|
|
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.
|
|
|
|
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>
|
|
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>yocto-layer</filename> tool to create
|
|
a "generic" layer.
|
|
For information on this tool, see the
|
|
"<ulink url='&YOCTO_DOCS_DEV_URL;#creating-a-general-layer-using-the-yocto-layer-script'>Creating a General Layer Using the yocto-layer Script</ulink>"
|
|
section in the Yocto Project Development Guide.
|
|
</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
|
|
i386
|
|
x86_64
|
|
arm
|
|
qemu
|
|
mips
|
|
</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>
|
|
and are currently in the top-level folder of the
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
|
|
</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)
|
|
3
|
|
Would you like to use the default (3.10) kernel? (y/n) [default: y] 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-3.10.git...
|
|
Please choose a machine branch to base your new BSP branch on: [default: standard/base]
|
|
1) standard/arm-versatile-926ejs
|
|
2) standard/base
|
|
3) standard/beagleboard
|
|
4) standard/ck
|
|
5) standard/crownbay
|
|
6) standard/edf
|
|
7) standard/emenlow
|
|
8) standard/fri2
|
|
9) standard/fsl-mpc8315e-rdb
|
|
10) standard/minnow
|
|
11) standard/mti-malta32
|
|
12) standard/mti-malta64
|
|
13) standard/qemuppc
|
|
14) standard/routerstationpro
|
|
15) standard/sys940x
|
|
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>
|
|
Let's 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 3.10 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 (e.g. 3.2, 3.2_preempt-rt, and so forth.).</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
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#local-kernel-files'>Linux Yocto Kernel</ulink>
|
|
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_DEV_URL;#source-directory'>Source Directory</ulink>,
|
|
which is <filename>poky</filename> in this case.
|
|
</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-yocto \
|
|
/usr/local/src/yocto/meta-yocto-bsp \
|
|
/usr/local/src/yocto/meta-myarm \
|
|
"
|
|
|
|
BBLAYERS_NON_REMOVABLE ?= " \
|
|
/usr/local/src/yocto/meta \
|
|
/usr/local/src/yocto/meta-yocto \
|
|
"
|
|
</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
|
|
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 items:
|
|
CONFIG_MISC_DEVICES=y
|
|
|
|
$ yocto-kernel config add myarm CONFIG_YOCTO_TESTMOD=y
|
|
Added items:
|
|
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>
|