1655 lines
94 KiB
XML
1655 lines
94 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='dev-manual-model'>
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<title>Common Development Models</title>
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<para>
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Many development models exist for which you can use the Yocto Project.
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This chapter overviews simple methods that use tools provided by the
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Yocto Project:
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<itemizedlist>
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<listitem><para><emphasis>System Development:</emphasis>
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System Development covers Board Support Package (BSP) development
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and kernel modification or configuration.
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For an example on how to create a BSP, see the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>"
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section in the Yocto Project Board Support Package (BSP)
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Developer's Guide.
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For more complete information on how to work with the kernel,
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see the
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<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;'>Yocto Project Linux Kernel Development Manual</ulink>.
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</para></listitem>
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<listitem><para><emphasis>User Application Development:</emphasis>
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User Application Development covers development of applications
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that you intend to run on target hardware.
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For information on how to set up your host development system for
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user-space application development, see the
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<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>.
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For a simple example of user-space application development using
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the <trademark class='trade'>Eclipse</trademark> IDE, see the
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"<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-developing-applications-using-eclipse'>Developing Applications Using <trademark class='trade'>Eclipse</trademark></ulink>" section.
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</para></listitem>
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<listitem><para><emphasis>Temporary Source Code Modification:</emphasis>
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Direct modification of temporary source code is a convenient
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development model to quickly iterate and develop towards a
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solution.
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Once you implement the solution, you should of course take
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steps to get the changes upstream and applied in the affected
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recipes.
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</para></listitem>
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<listitem><para><emphasis>Image Development using Toaster:</emphasis>
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You can use <ulink url='&YOCTO_HOME_URL;/Tools-resources/projects/toaster'>Toaster</ulink>
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to build custom operating system images within the build
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environment.
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Toaster provides an efficient interface to the OpenEmbedded build
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that allows you to start builds and examine build statistics.
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</para></listitem>
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<listitem><para><emphasis>Using a Development Shell:</emphasis>
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You can use a
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<link linkend='platdev-appdev-devshell'><filename>devshell</filename></link>
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to efficiently debug
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commands or simply edit packages.
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Working inside a development shell is a quick way to set up the
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OpenEmbedded build environment to work on parts of a project.
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</para></listitem>
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</itemizedlist>
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</para>
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<section id='system-development-model'>
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<title>System Development Workflow</title>
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<para>
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System development involves modification or creation of an image that you want to run on
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a specific hardware target.
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Usually, when you want to create an image that runs on embedded hardware, the image does
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not require the same number of features that a full-fledged Linux distribution provides.
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Thus, you can create a much smaller image that is designed to use only the
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features for your particular hardware.
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</para>
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<para>
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To help you understand how system development works in the Yocto Project, this section
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covers two types of image development: BSP creation and kernel modification or
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configuration.
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</para>
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<section id='developing-a-board-support-package-bsp'>
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<title>Developing a Board Support Package (BSP)</title>
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<para>
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A BSP is a collection of recipes that, when applied during a build, results in
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an image that you can run on a particular board.
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Thus, the package when compiled into the new image, supports the operation of the board.
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</para>
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<note>
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For a brief list of terms used when describing the development process in the Yocto Project,
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see the "<link linkend='yocto-project-terms'>Yocto Project Terms</link>" section.
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</note>
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<para>
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The remainder of this section presents the basic
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steps used to create a BSP using the Yocto Project's
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<ulink url='&YOCTO_DOCS_BSP_URL;#using-the-yocto-projects-bsp-tools'>BSP Tools</ulink>.
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Although not required for BSP creation, the
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<filename>meta-intel</filename> repository, which contains
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many BSPs supported by the Yocto Project, is part of the example.
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</para>
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<para>
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For an example that shows how to create a new layer using the tools, see the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>"
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section in the Yocto Project Board Support Package (BSP) Developer's Guide.
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</para>
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<para>
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The following illustration and list summarize the BSP creation general workflow.
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</para>
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<para>
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<imagedata fileref="figures/bsp-dev-flow.png" width="6in" depth="7in" align="center" scalefit="1" />
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</para>
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<para>
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<orderedlist>
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<listitem><para><emphasis>Set up your host development system to support
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development using the Yocto Project</emphasis>: See the
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"<ulink url='&YOCTO_DOCS_QS_URL;#the-linux-distro'>The Linux Distribution</ulink>"
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and the
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"<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>" sections both
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in the Yocto Project Quick Start for requirements.</para></listitem>
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<listitem><para><emphasis>Establish a local copy of the project files on your
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system</emphasis>: You need this <link linkend='source-directory'>Source
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Directory</link> available on your host system.
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Having these files on your system gives you access to the build
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process and to the tools you need.
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For information on how to set up the Source Directory,
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see the
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"<link linkend='getting-setup'>Getting Set Up</link>" section.</para></listitem>
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<listitem><para><emphasis>Establish the <filename>meta-intel</filename>
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repository on your system</emphasis>: Having local copies
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of these supported BSP layers on your system gives you
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access to layers you might be able to build on or modify
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to create your BSP.
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For information on how to get these files, see the
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"<link linkend='getting-setup'>Getting Set Up</link>" section.</para></listitem>
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<listitem><para><emphasis>Create your own BSP layer using the
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<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'><filename>yocto-bsp</filename></ulink> script</emphasis>:
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Layers are ideal for
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isolating and storing work for a given piece of hardware.
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A layer is really just a location or area in which you place
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the recipes and configurations for your BSP.
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In fact, a BSP is, in itself, a special type of layer.
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The simplest way to create a new BSP layer that is compliant with the
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Yocto Project is to use the <filename>yocto-bsp</filename> script.
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For information about that script, see the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#creating-a-new-bsp-layer-using-the-yocto-bsp-script'>Creating a New BSP Layer Using the yocto-bsp Script</ulink>"
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section in the Yocto Project Board Support (BSP) Developer's Guide.
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</para>
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<para>
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Another example that illustrates a layer
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is an application.
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Suppose you are creating an application that has
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library or other dependencies in order for it to
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compile and run.
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The layer, in this case, would be where all the
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recipes that define those dependencies are kept.
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The key point for a layer is that it is an isolated
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area that contains all the relevant information for
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the project that the OpenEmbedded build system knows
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about.
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For more information on layers, see the
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"<link linkend='understanding-and-creating-layers'>Understanding and Creating Layers</link>"
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section.
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For more information on BSP layers, see the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
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section in the Yocto Project Board Support Package (BSP)
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Developer's Guide.
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<note>
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<para>
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Five BSPs exist that are part of the Yocto Project release:
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<filename>beaglebone</filename> (ARM),
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<filename>mpc8315e</filename> (PowerPC),
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and <filename>edgerouter</filename> (MIPS).
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The recipes and configurations for these five BSPs
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are located and dispersed within the
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<link linkend='source-directory'>Source Directory</link>.
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</para>
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<para>
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Three core Intel BSPs exist as part of the Yocto
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Project release in the
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<filename>meta-intel</filename> layer:
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<itemizedlist>
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<listitem><para><filename>intel-core2-32</filename>,
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which is a BSP optimized for the Core2 family of CPUs
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as well as all CPUs prior to the Silvermont core.
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</para></listitem>
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<listitem><para><filename>intel-corei7-64</filename>,
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which is a BSP optimized for Nehalem and later
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Core and Xeon CPUs as well as Silvermont and later
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Atom CPUs, such as the Baytrail SoCs.
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</para></listitem>
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<listitem><para><filename>intel-quark</filename>,
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which is a BSP optimized for the Intel Galileo
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gen1 & gen2 development boards.
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</para></listitem>
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</itemizedlist>
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</para>
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</note>
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</para>
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<para>When you set up a layer for a new BSP, you should follow a standard layout.
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This layout is described in the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-filelayout'>Example Filesystem Layout</ulink>"
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section of the Board Support Package (BSP) Development Guide.
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In the standard layout, you will notice a suggested structure for recipes and
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configuration information.
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You can see the standard layout for a BSP by examining
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any supported BSP found in the <filename>meta-intel</filename> layer inside
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the Source Directory.</para></listitem>
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<listitem><para><emphasis>Make configuration changes to your new BSP
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layer</emphasis>: The standard BSP layer structure organizes the files you need
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to edit in <filename>conf</filename> and several <filename>recipes-*</filename>
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directories within the BSP layer.
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Configuration changes identify where your new layer is on the local system
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and identify which kernel you are going to use.
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When you run the <filename>yocto-bsp</filename> script, you are able to interactively
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configure many things for the BSP (e.g. keyboard, touchscreen, and so forth).
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</para></listitem>
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<listitem><para><emphasis>Make recipe changes to your new BSP layer</emphasis>: Recipe
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changes include altering recipes (<filename>.bb</filename> files), removing
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recipes you do not use, and adding new recipes or append files
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(<filename>.bbappend</filename>) that you need to support your hardware.
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</para></listitem>
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<listitem><para><emphasis>Prepare for the build</emphasis>: Once you have made all the
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changes to your BSP layer, there remains a few things
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you need to do for the OpenEmbedded build system in order for it to create your image.
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You need to get the build environment ready by sourcing an environment setup script
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(i.e. <filename>oe-init-build-env</filename> or
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<filename>oe-init-build-env-memres</filename>)
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and you need to be sure two key configuration files are configured appropriately:
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the <filename>conf/local.conf</filename> and the
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<filename>conf/bblayers.conf</filename> file.
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You must make the OpenEmbedded build system aware of your new layer.
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See the
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"<link linkend='enabling-your-layer'>Enabling Your Layer</link>" section
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for information on how to let the build system know about your new layer.</para>
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<para>The entire process for building an image is overviewed in the section
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"<ulink url='&YOCTO_DOCS_QS_URL;#qs-building-images'>Building Images</ulink>" section
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of the Yocto Project Quick Start.
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You might want to reference this information.</para></listitem>
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<listitem><para><emphasis>Build the image</emphasis>: The OpenEmbedded build system
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uses the BitBake tool to build images based on the type of image you want to create.
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You can find more information about BitBake in the
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<ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
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</para>
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<para>The build process supports several types of images to satisfy different needs.
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See the
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"<ulink url='&YOCTO_DOCS_REF_URL;#ref-images'>Images</ulink>" chapter
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in the Yocto Project Reference Manual for information on
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supported images.</para></listitem>
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</orderedlist>
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</para>
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<para>
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You can view a video presentation on "Building Custom Embedded Images with Yocto"
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at <ulink url='http://free-electrons.com/blog/elc-2011-videos'>Free Electrons</ulink>.
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After going to the page, just search for "Embedded".
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You can also find supplemental information in the
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<ulink url='&YOCTO_DOCS_BSP_URL;'>
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Yocto Project Board Support Package (BSP) Developer's Guide</ulink>.
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Finally, there is helpful material and links on this
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<ulink url='&YOCTO_WIKI_URL;/wiki/Transcript:_creating_one_generic_Atom_BSP_from_another'>wiki page</ulink>.
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Although a bit dated, you might find the information on the wiki
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helpful.
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</para>
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</section>
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<section id='modifying-the-kernel'>
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<title><anchor id='kernel-spot' />Modifying the Kernel</title>
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<para>
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Kernel modification involves changing the Yocto Project kernel, which could involve changing
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configuration options as well as adding new kernel recipes.
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Configuration changes can be added in the form of configuration fragments, while recipe
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modification comes through the kernel's <filename>recipes-kernel</filename> area
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in a kernel layer you create.
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</para>
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<para>
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The remainder of this section presents a high-level overview of the Yocto Project
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kernel architecture and the steps to modify the kernel.
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You can reference the
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"<link linkend='patching-the-kernel'>Patching the Kernel</link>" section
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for an example that changes the source code of the kernel.
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For information on how to configure the kernel, see the
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"<link linkend='configuring-the-kernel'>Configuring the Kernel</link>" section.
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For more information on the kernel and on modifying the kernel, see the
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<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;'>Yocto Project Linux Kernel Development Manual</ulink>.
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</para>
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<section id='kernel-overview'>
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<title>Kernel Overview</title>
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<para>
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Traditionally, when one thinks of a patched kernel, they think of a base kernel
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source tree and a fixed structure that contains kernel patches.
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The Yocto Project, however, employs mechanisms that, in a sense, result in a kernel source
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generator.
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By the end of this section, this analogy will become clearer.
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</para>
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<para>
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You can find a web interface to the Yocto Project kernel source repositories at
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<ulink url='&YOCTO_GIT_URL;'></ulink>.
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If you look at the interface, you will see to the left a grouping of
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Git repositories titled "Yocto Linux Kernel."
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Within this group, you will find several kernels supported by
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the Yocto Project:
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<itemizedlist>
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<listitem><para><emphasis>
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<filename>linux-yocto-3.14</filename></emphasis> - The
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stable Yocto Project kernel to use with the Yocto
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Project Releases 1.6 and 1.7.
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This kernel is based on the Linux 3.14 released kernel.
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</para></listitem>
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<listitem><para><emphasis>
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<filename>linux-yocto-3.17</filename></emphasis> - An
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additional, unsupported Yocto Project kernel used with
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the Yocto Project Release 1.7.
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This kernel is based on the Linux 3.17 released kernel.
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</para></listitem>
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<listitem><para><emphasis>
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<filename>linux-yocto-3.19</filename></emphasis> - The
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stable Yocto Project kernel to use with the Yocto
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Project Release 1.8.
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This kernel is based on the Linux 3.19 released kernel.
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</para></listitem>
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<listitem><para><emphasis>
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<filename>linux-yocto-4.1</filename></emphasis> - The
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stable Yocto Project kernel to use with the Yocto
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Project Release 2.0.
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This kernel is based on the Linux 4.1 released kernel.
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</para></listitem>
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<listitem><para><emphasis>
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<filename>linux-yocto-4.4</filename></emphasis> - The
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stable Yocto Project kernel to use with the Yocto
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Project Release 2.1.
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This kernel is based on the Linux 4.4 released kernel.
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</para></listitem>
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<listitem><para><emphasis>
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<filename>linux-yocto-dev</filename></emphasis> - A
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development kernel based on the latest upstream release
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candidate available.
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</para></listitem>
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</itemizedlist>
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<note>
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Long Term Support Initiative (LTSI) for Yocto Project kernels
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is as follows:
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<itemizedlist>
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<listitem><para>For Yocto Project releases 1.7, 1.8, and 2.0,
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the LTSI kernel is <filename>linux-yocto-3.14</filename>.
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</para></listitem>
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<listitem><para>For Yocto Project release 2.1, the
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LTSI kernel is <filename>linux-yocto-4.1</filename>.
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</para></listitem>
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</itemizedlist>
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</note>
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</para>
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<para>
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The kernels are maintained using the Git revision control system
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that structures them using the familiar "tree", "branch", and "leaf" scheme.
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Branches represent diversions from general code to more specific code, while leaves
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represent the end-points for a complete and unique kernel whose source files,
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when gathered from the root of the tree to the leaf, accumulate to create the files
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necessary for a specific piece of hardware and its features.
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The following figure displays this concept:
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<para>
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<imagedata fileref="figures/kernel-overview-1.png"
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width="6in" depth="6in" align="center" scale="100" />
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</para>
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<para>
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Within the figure, the "Kernel.org Branch Point" represents the point in the tree
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where a supported base kernel is modified from the Linux kernel.
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For example, this could be the branch point for the <filename>linux-yocto-3.19</filename>
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kernel.
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Thus, everything further to the right in the structure is based on the
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<filename>linux-yocto-3.19</filename> kernel.
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Branch points to the right in the figure represent where the
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<filename>linux-yocto-3.19</filename> kernel is modified for specific hardware
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or types of kernels, such as real-time kernels.
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Each leaf thus represents the end-point for a kernel designed to run on a specific
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targeted device.
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</para>
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<para>
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The overall result is a Git-maintained repository from which all the supported
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kernel types can be derived for all the supported devices.
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A big advantage to this scheme is the sharing of common features by keeping them in
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"larger" branches within the tree.
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This practice eliminates redundant storage of similar features shared among kernels.
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</para>
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<note>
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Keep in mind the figure does not take into account all the supported Yocto
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Project kernel types, but rather shows a single generic kernel just for conceptual purposes.
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Also keep in mind that this structure represents the Yocto Project source repositories
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that are either pulled from during the build or established on the host development system
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prior to the build by either cloning a particular kernel's Git repository or by
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downloading and unpacking a tarball.
|
|
</note>
|
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<para>
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Upstream storage of all the available kernel source code is one thing, while
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representing and using the code on your host development system is another.
|
|
Conceptually, you can think of the kernel source repositories as all the
|
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source files necessary for all the supported kernels.
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As a developer, you are just interested in the source files for the kernel on
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which you are working.
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And, furthermore, you need them available on your host system.
|
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</para>
|
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<para>
|
|
Kernel source code is available on your host system a couple of different
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ways.
|
|
If you are working in the kernel all the time, you probably would want
|
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to set up your own local Git repository of the kernel tree.
|
|
If you just need to make some patches to the kernel, you can access
|
|
temporary kernel source files that were extracted and used
|
|
during a build.
|
|
We will just talk about working with the temporary source code.
|
|
For more information on how to get kernel source code onto your
|
|
host system, see the
|
|
"<link linkend='local-kernel-files'>Yocto Project Kernel</link>"
|
|
bulleted item earlier in the manual.
|
|
</para>
|
|
|
|
<para>
|
|
What happens during the build?
|
|
When you build the kernel on your development system, all files needed for the build
|
|
are taken from the source repositories pointed to by the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink> variable
|
|
and gathered in a temporary work area
|
|
where they are subsequently used to create the unique kernel.
|
|
Thus, in a sense, the process constructs a local source tree specific to your
|
|
kernel to generate the new kernel image - a source generator if you will.
|
|
</para>
|
|
The following figure shows the temporary file structure
|
|
created on your host system when the build occurs.
|
|
This
|
|
<link linkend='build-directory'>Build Directory</link> contains all the
|
|
source files used during the build.
|
|
</para>
|
|
|
|
<para>
|
|
<imagedata fileref="figures/kernel-overview-2-generic.png"
|
|
width="6in" depth="5in" align="center" scale="100" />
|
|
</para>
|
|
|
|
<para>
|
|
Again, for additional information on the Yocto Project kernel's
|
|
architecture and its branching strategy, see the
|
|
<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;'>Yocto Project Linux Kernel Development Manual</ulink>.
|
|
You can also reference the
|
|
"<link linkend='patching-the-kernel'>Patching the Kernel</link>"
|
|
section for a detailed example that modifies the kernel.
|
|
</para>
|
|
</section>
|
|
|
|
<section id='kernel-modification-workflow'>
|
|
<title>Kernel Modification Workflow</title>
|
|
|
|
<para>
|
|
This illustration and the following list summarizes the kernel modification general workflow.
|
|
</para>
|
|
|
|
<para>
|
|
<imagedata fileref="figures/kernel-dev-flow.png"
|
|
width="6in" 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
|
|
"<ulink url='&YOCTO_DOCS_QS_URL;#the-linux-distro'>The Linux Distribution</ulink>" and
|
|
"<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Build Host Packages</ulink>" sections both
|
|
in the Yocto Project Quick Start for requirements.</para></listitem>
|
|
<listitem><para><emphasis>Establish a local copy of project files on your
|
|
system</emphasis>: Having the <link linkend='source-directory'>Source
|
|
Directory</link> on your system gives you access to the build process and tools
|
|
you need.
|
|
For information on how to get these files, see the bulleted item
|
|
"<link linkend='local-yp-release'>Yocto Project Release</link>" earlier in this manual.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Establish the temporary kernel source files</emphasis>:
|
|
Temporary kernel source files are kept in the
|
|
<link linkend='build-directory'>Build Directory</link>
|
|
created by the
|
|
OpenEmbedded build system when you run BitBake.
|
|
If you have never built the kernel in which you are
|
|
interested, you need to run an initial build to
|
|
establish local kernel source files.</para>
|
|
<para>If you are building an image for the first time, you need to get the build
|
|
environment ready by sourcing an environment setup script
|
|
(i.e. <filename>oe-init-build-env</filename> or
|
|
<filename>oe-init-build-env-memres</filename>).
|
|
You also need to be sure two key configuration files
|
|
(<filename>local.conf</filename> and <filename>bblayers.conf</filename>)
|
|
are configured appropriately.</para>
|
|
<para>The entire process for building an image is overviewed in the
|
|
"<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.
|
|
You can find more information on 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>
|
|
<listitem><para><emphasis>Make changes to the kernel source code if
|
|
applicable</emphasis>: Modifying the kernel does not always mean directly
|
|
changing source files.
|
|
However, if you have to do this, you make the changes to the files in the
|
|
Build Directory.</para></listitem>
|
|
<listitem><para><emphasis>Make kernel configuration changes if applicable</emphasis>:
|
|
If your situation calls for changing the kernel's
|
|
configuration, you can use
|
|
<ulink url='&YOCTO_DOCS_KERNEL_DEV_URL;#generating-configuration-files'><filename>menuconfig</filename></ulink>,
|
|
which allows you to interactively develop and test the
|
|
configuration changes you are making to the kernel.
|
|
Saving changes you make with
|
|
<filename>menuconfig</filename> updates
|
|
the kernel's <filename>.config</filename> file.
|
|
<note><title>Warning</title>
|
|
Try to resist the temptation to directly edit an
|
|
existing <filename>.config</filename> file, which is
|
|
found in the Build Directory at
|
|
<filename>tmp/sysroots/<replaceable>machine-name</replaceable>/kernel</filename>.
|
|
Doing so, can produce unexpected results when the
|
|
OpenEmbedded build system regenerates the configuration
|
|
file.
|
|
</note>
|
|
Once you are satisfied with the configuration
|
|
changes made using <filename>menuconfig</filename>
|
|
and you have saved them, you can directly compare the
|
|
resulting <filename>.config</filename> file against an
|
|
existing original and gather those changes into a
|
|
<link linkend='creating-config-fragments'>configuration fragment file</link>
|
|
to be referenced from within the kernel's
|
|
<filename>.bbappend</filename> file.</para>
|
|
|
|
<para>Additionally, if you are working in a BSP layer
|
|
and need to modify the BSP's kernel's configuration,
|
|
you can use the
|
|
<ulink url='&YOCTO_DOCS_BSP_URL;#managing-kernel-patches-and-config-items-with-yocto-kernel'><filename>yocto-kernel</filename></ulink>
|
|
script as well as <filename>menuconfig</filename>.
|
|
The <filename>yocto-kernel</filename> script lets
|
|
you interactively set up kernel configurations.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Rebuild the kernel image with your changes</emphasis>:
|
|
Rebuilding the kernel image applies your changes.
|
|
</para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='application-development-workflow-using-an-sdk'>
|
|
<title>Application Development Workflow Using an SDK</title>
|
|
|
|
<para>
|
|
Standard and extensible Software Development Kits (SDK) make it easy
|
|
to develop applications inside or outside of the Yocto Project
|
|
development environment.
|
|
Tools exist to help the application developer during any phase
|
|
of development.
|
|
For information on how to install and use an SDK, see the
|
|
<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-intro'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="dev-modifying-source-code">
|
|
<title>Modifying Source Code</title>
|
|
|
|
<para>
|
|
A common development workflow consists of modifying project source
|
|
files that are external to the Yocto Project and then integrating
|
|
that project's build output into an image built using the
|
|
OpenEmbedded build system.
|
|
Given this scenario, development engineers typically want to stick
|
|
to their familiar project development tools and methods, which allows
|
|
them to just focus on the project.
|
|
</para>
|
|
|
|
<para>
|
|
Several workflows exist that allow you to develop, build, and test
|
|
code that is going to be integrated into an image built using the
|
|
OpenEmbedded build system.
|
|
This section describes two:
|
|
<itemizedlist>
|
|
<listitem><para><emphasis><filename>devtool</filename>:</emphasis>
|
|
A set of tools to aid in working on the source code built by
|
|
the OpenEmbedded build system.
|
|
Section
|
|
"<link linkend='using-devtool-in-your-workflow'>Using <filename>devtool</filename> in Your Workflow</link>"
|
|
describes this workflow.
|
|
If you want more information that showcases the workflow, click
|
|
<ulink url='https://drive.google.com/a/linaro.org/file/d/0B3KGzY5fW7laTDVxUXo3UDRvd2s/view'>here</ulink>
|
|
for a presentation by Trevor Woerner that, while somewhat dated,
|
|
provides detailed background information and a complete
|
|
working tutorial.
|
|
</para></listitem>
|
|
<listitem><para><emphasis><ulink url='http://savannah.nongnu.org/projects/quilt'>Quilt</ulink>:</emphasis>
|
|
A powerful tool that allows you to capture source
|
|
code changes without having a clean source tree.
|
|
While Quilt is not the preferred workflow of the two, this
|
|
section includes it for users that are committed to using
|
|
the tool.
|
|
See the
|
|
"<link linkend='using-a-quilt-workflow'>Using Quilt in Your Workflow</link>"
|
|
section for more information.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<section id='using-devtool-in-your-workflow'>
|
|
<title>Using <filename>devtool</filename> in Your Workflow</title>
|
|
|
|
<para>
|
|
As mentioned earlier, <filename>devtool</filename> helps
|
|
you easily develop projects whose build output must be part of
|
|
an image built using the OpenEmbedded build system.
|
|
</para>
|
|
|
|
<para>
|
|
Three entry points exist that allow you to develop using
|
|
<filename>devtool</filename>:
|
|
<itemizedlist>
|
|
<listitem><para><emphasis><filename>devtool add</filename></emphasis>
|
|
</para></listitem>
|
|
<listitem><para><emphasis><filename>devtool modify</filename></emphasis>
|
|
</para></listitem>
|
|
<listitem><para><emphasis><filename>devtool upgrade</filename></emphasis>
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
The remainder of this section presents these workflows.
|
|
See the
|
|
"<ulink url='&YOCTO_DOCS_REF_URL;#ref-devtool-reference'><filename>devtool</filename> Quick Reference</ulink>"
|
|
in the Yocto Project Reference Manual for a
|
|
<filename>devtool</filename> quick reference.
|
|
</para>
|
|
|
|
<section id='use-devtool-to-integrate-new-code'>
|
|
<title>Use <filename>devtool add</filename> to Add an Application</title>
|
|
|
|
<para>
|
|
The <filename>devtool add</filename> command generates
|
|
a new recipe based on existing source code.
|
|
This command takes advantage of the
|
|
<ulink url='&YOCTO_DOCS_DEV_URL;#devtool-the-workspace-layer-structure'>workspace</ulink>
|
|
layer that many <filename>devtool</filename> commands
|
|
use.
|
|
The command is flexible enough to allow you to extract source
|
|
code into both the workspace or a separate local Git repository
|
|
and to use existing code that does not need to be extracted.
|
|
</para>
|
|
|
|
<para>
|
|
Depending on your particular scenario, the arguments and options
|
|
you use with <filename>devtool add</filename> form different
|
|
combinations.
|
|
The following diagram shows common development flows
|
|
you would use with the <filename>devtool add</filename>
|
|
command:
|
|
</para>
|
|
|
|
<para>
|
|
<imagedata fileref="figures/devtool-add-flow.png" align="center" />
|
|
</para>
|
|
|
|
<para>
|
|
<orderedlist>
|
|
<listitem><para><emphasis>Generating the New Recipe</emphasis>:
|
|
The top part of the flow shows three scenarios by which
|
|
you could use <filename>devtool add</filename> to
|
|
generate a recipe based on existing source code.</para>
|
|
|
|
<para>In a shared development environment, it is
|
|
typical where other developers are responsible for
|
|
various areas of source code.
|
|
As a developer, you are probably interested in using
|
|
that source code as part of your development using
|
|
the Yocto Project.
|
|
All you need is access to the code, a recipe, and a
|
|
controlled area in which to do your work.</para>
|
|
|
|
<para>Within the diagram, three possible scenarios
|
|
feed into the <filename>devtool add</filename> workflow:
|
|
<itemizedlist>
|
|
<listitem><para><emphasis>Left</emphasis>:
|
|
The left scenario represents a common situation
|
|
where the source code does not exist locally
|
|
and needs to be extracted.
|
|
In this situation, you just let it get
|
|
extracted to the default workspace - you do not
|
|
want it in some specific location outside of the
|
|
workspace.
|
|
Thus, everything you need will be located in the
|
|
workspace:
|
|
<literallayout class='monospaced'>
|
|
$ devtool add <replaceable>recipe fetchuri</replaceable>
|
|
</literallayout>
|
|
With this command, <filename>devtool</filename>
|
|
creates a recipe and an append file in the
|
|
workspace as well as extracts the upstream
|
|
source files into a local Git repository also
|
|
within the <filename>sources</filename> folder.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Middle</emphasis>:
|
|
The middle scenario also represents a situation where
|
|
the source code does not exist locally.
|
|
In this case, the code is again upstream
|
|
and needs to be extracted to some
|
|
local area - this time outside of the default
|
|
workspace.
|
|
If required, <filename>devtool</filename>
|
|
always creates
|
|
a Git repository locally during the extraction.
|
|
Furthermore, the first positional argument
|
|
<replaceable>srctree</replaceable> in this case
|
|
identifies where the
|
|
<filename>devtool add</filename> command
|
|
will locate the extracted code outside of the
|
|
workspace:
|
|
<literallayout class='monospaced'>
|
|
$ devtool add <replaceable>recipe srctree fetchuri</replaceable>
|
|
</literallayout>
|
|
In summary, the source code is pulled from
|
|
<replaceable>fetchuri</replaceable> and extracted
|
|
into the location defined by
|
|
<replaceable>srctree</replaceable> as a local
|
|
Git repository.</para>
|
|
|
|
<para>Within workspace, <filename>devtool</filename>
|
|
creates both the recipe and an append file
|
|
for the recipe.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Right</emphasis>:
|
|
The right scenario represents a situation
|
|
where the source tree (srctree) has been
|
|
previously prepared outside of the
|
|
<filename>devtool</filename> workspace.
|
|
</para>
|
|
|
|
<para>The following command names the recipe
|
|
and identifies where the existing source tree
|
|
is located:
|
|
<literallayout class='monospaced'>
|
|
$ devtool add <replaceable>recipe srctree</replaceable>
|
|
</literallayout>
|
|
The command examines the source code and creates
|
|
a recipe for it placing the recipe into the
|
|
workspace.</para>
|
|
|
|
<para>Because the extracted source code already exists,
|
|
<filename>devtool</filename> does not try to
|
|
relocate it into the workspace - just the new
|
|
the recipe is placed in the workspace.</para>
|
|
|
|
<para>Aside from a recipe folder, the command
|
|
also creates an append folder and places an initial
|
|
<filename>*.bbappend</filename> within.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Edit the Recipe</emphasis>:
|
|
At this point, you can use <filename>devtool edit-recipe</filename>
|
|
to open up the editor as defined by the
|
|
<filename>$EDITOR</filename> environment variable
|
|
and modify the file:
|
|
<literallayout class='monospaced'>
|
|
$ devtool edit-recipe <replaceable>recipe</replaceable>
|
|
</literallayout>
|
|
From within the editor, you can make modifications to the
|
|
recipe that take affect when you build it later.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Build the Recipe or Rebuild the Image</emphasis>:
|
|
At this point in the flow, the next step you
|
|
take depends on what you are going to do with
|
|
the new code.</para>
|
|
<para>If you need to take the build output and eventually
|
|
move it to the target hardware, you would use
|
|
<filename>devtool build</filename>:
|
|
<literallayout class='monospaced'>
|
|
$ devtool build <replaceable>recipe</replaceable>
|
|
</literallayout></para>
|
|
<para>On the other hand, if you want an image to
|
|
contain the recipe's packages for immediate deployment
|
|
onto a device (e.g. for testing purposes), you can use
|
|
the <filename>devtool build-image</filename> command:
|
|
<literallayout class='monospaced'>
|
|
$ devtool build-image <replaceable>image</replaceable>
|
|
</literallayout>
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Deploy the Build Output</emphasis>:
|
|
When you use the <filename>devtool build</filename>
|
|
command to build out your recipe, you probably want to
|
|
see if the resulting build output works as expected on target
|
|
hardware.
|
|
<note>
|
|
This step assumes you have a previously built
|
|
image that is already either running in QEMU or
|
|
running on actual hardware.
|
|
Also, it is assumed that for deployment of the image
|
|
to the target, SSH is installed in the image and if
|
|
the image is running on real hardware that you have
|
|
network access to and from your development machine.
|
|
</note>
|
|
You can deploy your build output to that target hardware by
|
|
using the <filename>devtool deploy-target</filename> command:
|
|
<literallayout class='monospaced'>
|
|
$ devtool deploy-target <replaceable>recipe target</replaceable>
|
|
</literallayout>
|
|
The <replaceable>target</replaceable> is a live target machine
|
|
running as an SSH server.</para>
|
|
|
|
<para>You can, of course, also deploy the image you build
|
|
using the <filename>devtool build-image</filename> command
|
|
to actual hardware.
|
|
However, <filename>devtool</filename> does not provide a
|
|
specific command that allows you to do this.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<emphasis>Finish Your Work With the Recipe</emphasis>:
|
|
The <filename>devtool finish</filename> command creates
|
|
any patches corresponding to commits in the local
|
|
Git repository, moves the new recipe to a more permanent
|
|
layer, and then resets the recipe so that the recipe is
|
|
built normally rather than from the workspace.
|
|
<literallayout class='monospaced'>
|
|
$ devtool finish <replaceable>recipe layer</replaceable>
|
|
</literallayout>
|
|
<note>
|
|
Any changes you want to turn into patches must be
|
|
committed to the Git repository in the source tree.
|
|
</note></para>
|
|
|
|
<para>As mentioned, the <filename>devtool finish</filename>
|
|
command moves the final recipe to its permanent layer.
|
|
</para>
|
|
|
|
<para>As a final process of the
|
|
<filename>devtool finish</filename> command, the state
|
|
of the standard layers and the upstream source is
|
|
restored so that you can build the recipe from those
|
|
areas rather than the workspace.
|
|
<note>
|
|
You can use the <filename>devtool reset</filename>
|
|
command to put things back should you decide you
|
|
do not want to proceed with your work.
|
|
If you do use this command, realize that the source
|
|
tree is preserved.
|
|
</note>
|
|
</para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='devtool-use-devtool-modify-to-enable-work-on-code-associated-with-an-existing-recipe'>
|
|
<title>Use <filename>devtool modify</filename> to Modify the Source of an Existing Component</title>
|
|
|
|
<para>
|
|
The <filename>devtool modify</filename> command prepares the
|
|
way to work on existing code that already has a recipe in
|
|
place.
|
|
The command is flexible enough to allow you to extract code,
|
|
specify the existing recipe, and keep track of and gather any
|
|
patch files from other developers that are
|
|
associated with the code.
|
|
</para>
|
|
|
|
<para>
|
|
Depending on your particular scenario, the arguments and options
|
|
you use with <filename>devtool modify</filename> form different
|
|
combinations.
|
|
The following diagram shows common development flows
|
|
you would use with the <filename>devtool modify</filename>
|
|
command:
|
|
</para>
|
|
|
|
<para>
|
|
<imagedata fileref="figures/devtool-modify-flow.png" align="center" />
|
|
</para>
|
|
|
|
<para>
|
|
<orderedlist>
|
|
<listitem><para><emphasis>Preparing to Modify the Code</emphasis>:
|
|
The top part of the flow shows three scenarios by which
|
|
you could use <filename>devtool modify</filename> to
|
|
prepare to work on source files.
|
|
Each scenario assumes the following:
|
|
<itemizedlist>
|
|
<listitem><para>The recipe exists in some layer external
|
|
to the <filename>devtool</filename> workspace.
|
|
</para></listitem>
|
|
<listitem><para>The source files exist upstream in an
|
|
un-extracted state or locally in a previously
|
|
extracted state.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
The typical situation is where another developer has
|
|
created some layer for use with the Yocto Project and
|
|
their recipe already resides in that layer.
|
|
Furthermore, their source code is readily available
|
|
either upstream or locally.
|
|
<itemizedlist>
|
|
<listitem><para><emphasis>Left</emphasis>:
|
|
The left scenario represents a common situation
|
|
where the source code does not exist locally
|
|
and needs to be extracted.
|
|
In this situation, the source is extracted
|
|
into the default workspace location.
|
|
The recipe, in this scenario, is in its own
|
|
layer outside the workspace
|
|
(i.e.
|
|
<filename>meta-</filename><replaceable>layername</replaceable>).
|
|
</para>
|
|
|
|
<para>The following command identifies the recipe
|
|
and by default extracts the source files:
|
|
<literallayout class='monospaced'>
|
|
$ devtool modify <replaceable>recipe</replaceable>
|
|
</literallayout>
|
|
Once <filename>devtool</filename>locates the recipe,
|
|
it uses the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
|
|
variable to locate the source code and
|
|
any local patch files from other developers are
|
|
located.
|
|
<note>
|
|
You cannot provide an URL for
|
|
<replaceable>srctree</replaceable> when using the
|
|
<filename>devtool modify</filename> command.
|
|
</note>
|
|
With this scenario, however, since no
|
|
<replaceable>srctree</replaceable> argument exists, the
|
|
<filename>devtool modify</filename> command by default
|
|
extracts the source files to a Git structure.
|
|
Furthermore, the location for the extracted source is the
|
|
default area within the workspace.
|
|
The result is that the command sets up both the source
|
|
code and an append file within the workspace with the
|
|
recipe remaining in its original location.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Middle</emphasis>:
|
|
The middle scenario represents a situation where
|
|
the source code also does not exist locally.
|
|
In this case, the code is again upstream
|
|
and needs to be extracted to some
|
|
local area as a Git repository.
|
|
The recipe, in this scenario, is again in its own
|
|
layer outside the workspace.</para>
|
|
|
|
<para>The following command tells
|
|
<filename>devtool</filename> what recipe with
|
|
which to work and, in this case, identifies a local
|
|
area for the extracted source files that is outside
|
|
of the default workspace:
|
|
<literallayout class='monospaced'>
|
|
$ devtool modify <replaceable>recipe srctree</replaceable>
|
|
</literallayout>
|
|
As with all extractions, the command uses
|
|
the recipe's <filename>SRC_URI</filename> to locate the
|
|
source files.
|
|
Once the files are located, the command by default
|
|
extracts them.
|
|
Providing the <replaceable>srctree</replaceable>
|
|
argument instructs <filename>devtool</filename> where
|
|
place the extracted source.</para>
|
|
|
|
<para>Within workspace, <filename>devtool</filename>
|
|
creates an append file for the recipe.
|
|
The recipe remains in its original location but
|
|
the source files are extracted to the location you
|
|
provided with <replaceable>srctree</replaceable>.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Right</emphasis>:
|
|
The right scenario represents a situation
|
|
where the source tree
|
|
(<replaceable>srctree</replaceable>) exists as a
|
|
previously extracted Git structure outside of
|
|
the <filename>devtool</filename> workspace.
|
|
In this example, the recipe also exists
|
|
elsewhere in its own layer.
|
|
</para>
|
|
|
|
<para>The following command tells
|
|
<filename>devtool</filename> the recipe
|
|
with which to work, uses the "-n" option to indicate
|
|
source does not need to be extracted, and uses
|
|
<replaceable>srctree</replaceable> to point to the
|
|
previously extracted source files:
|
|
<literallayout class='monospaced'>
|
|
$ devtool modify -n <replaceable>recipe srctree</replaceable>
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>Once the command finishes, it creates only
|
|
an append file for the recipe in the workspace.
|
|
The recipe and the source code remain in their
|
|
original locations.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Edit the Source</emphasis>:
|
|
Once you have used the <filename>devtool modify</filename>
|
|
command, you are free to make changes to the source
|
|
files.
|
|
You can use any editor you like to make and save
|
|
your source code modifications.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Build the Recipe</emphasis>:
|
|
Once you have updated the source files, you can build
|
|
the recipe.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Deploy the Build Output</emphasis>:
|
|
When you use the <filename>devtool build</filename>
|
|
command to build out your recipe, you probably want to see
|
|
if the resulting build output works as expected on target
|
|
hardware.
|
|
<note>
|
|
This step assumes you have a previously built
|
|
image that is already either running in QEMU or
|
|
running on actual hardware.
|
|
Also, it is assumed that for deployment of the image
|
|
to the target, SSH is installed in the image and if
|
|
the image is running on real hardware that you have
|
|
network access to and from your development machine.
|
|
</note>
|
|
You can deploy your build output to that target hardware by
|
|
using the <filename>devtool deploy-target</filename> command:
|
|
<literallayout class='monospaced'>
|
|
$ devtool deploy-target <replaceable>recipe target</replaceable>
|
|
</literallayout>
|
|
The <replaceable>target</replaceable> is a live target machine
|
|
running as an SSH server.</para>
|
|
|
|
<para>You can, of course, also deploy the image you build
|
|
using the <filename>devtool build-image</filename> command
|
|
to actual hardware.
|
|
However, <filename>devtool</filename> does not provide a
|
|
specific command that allows you to do this.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<emphasis>Finish Your Work With the Recipe</emphasis>:
|
|
The <filename>devtool finish</filename> command creates
|
|
any patches corresponding to commits in the local
|
|
Git repository, updates the recipe to point to them
|
|
(or creates a <filename>.bbappend</filename> file to do
|
|
so, depending on the specified destination layer), and
|
|
then resets the recipe so that the recipe is built normally
|
|
rather than from the workspace.
|
|
<literallayout class='monospaced'>
|
|
$ devtool finish <replaceable>recipe layer</replaceable>
|
|
</literallayout>
|
|
<note>
|
|
Any changes you want to turn into patches must be
|
|
committed to the Git repository in the source tree.
|
|
</note></para>
|
|
|
|
<para>Because there is no need to move the recipe,
|
|
<filename>devtool finish</filename> either updates the
|
|
original recipe in the original layer or the command
|
|
creates a <filename>.bbappend</filename> in a different
|
|
layer as provided by <replaceable>layer</replaceable>.
|
|
</para>
|
|
|
|
<para>As a final process of the
|
|
<filename>devtool finish</filename> command, the state
|
|
of the standard layers and the upstream source is
|
|
restored so that you can build the recipe from those
|
|
areas rather than the workspace.
|
|
<note>
|
|
You can use the <filename>devtool reset</filename>
|
|
command to put things back should you decide you
|
|
do not want to proceed with your work.
|
|
If you do use this command, realize that the source
|
|
tree is preserved.
|
|
</note>
|
|
</para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='devtool-use-devtool-upgrade-to-create-a-version-of-the-recipe-that-supports-a-newer-version-of-the-software'>
|
|
<title>Use <filename>devtool upgrade</filename> to Create a Version of the Recipe that Supports a Newer Version of the Software</title>
|
|
|
|
<para>
|
|
The <filename>devtool upgrade</filename> command updates
|
|
an existing recipe so that you can build it for an updated
|
|
set of source files.
|
|
The command is flexible enough to allow you to specify
|
|
source code revision and versioning schemes, extract code into
|
|
or out of the <filename>devtool</filename> workspace, and
|
|
work with any source file forms that the fetchers support.
|
|
</para>
|
|
|
|
<para>
|
|
Depending on your particular scenario, the arguments and options
|
|
you use with <filename>devtool upgrade</filename> form different
|
|
combinations.
|
|
The following diagram shows a common development flow
|
|
you would use with the <filename>devtool modify</filename>
|
|
command:
|
|
</para>
|
|
|
|
<para>
|
|
<imagedata fileref="figures/devtool-upgrade-flow.png" align="center" />
|
|
</para>
|
|
|
|
<para>
|
|
<orderedlist>
|
|
<listitem><para><emphasis>Initiate the Upgrade</emphasis>:
|
|
The top part of the flow shows a typical scenario by which
|
|
you could use <filename>devtool upgrade</filename>.
|
|
The following conditions exist:
|
|
<itemizedlist>
|
|
<listitem><para>The recipe exists in some layer external
|
|
to the <filename>devtool</filename> workspace.
|
|
</para></listitem>
|
|
<listitem><para>The source files for the new release
|
|
exist adjacent to the same location pointed to by
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
|
|
in the recipe (e.g. a tarball with the new version
|
|
number in the name, or as a different revision in
|
|
the upstream Git repository).
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
A common situation is where third-party software has
|
|
undergone a revision so that it has been upgraded.
|
|
The recipe you have access to is likely in your own layer.
|
|
Thus, you need to upgrade the recipe to use the
|
|
newer version of the software:
|
|
<literallayout class='monospaced'>
|
|
$ devtool upgrade -V <replaceable>version recipe</replaceable>
|
|
</literallayout>
|
|
By default, the <filename>devtool upgrade</filename> command
|
|
extracts source code into the <filename>sources</filename>
|
|
directory in the workspace.
|
|
If you want the code extracted to any other location, you
|
|
need to provide the <replaceable>srctree</replaceable>
|
|
positional argument with the command as follows:
|
|
<literallayout class='monospaced'>
|
|
$ devtool upgrade -V <replaceable>version recipe srctree</replaceable>
|
|
</literallayout>
|
|
Also, in this example, the "-V" option is used to specify
|
|
the new version.
|
|
If the source files pointed to by the
|
|
<filename>SRC_URI</filename> statement in the recipe are
|
|
in a Git repository, you must provide the "-S" option and
|
|
specify a revision for the software.</para>
|
|
|
|
<para>Once <filename>devtool</filename> locates the recipe,
|
|
it uses the <filename>SRC_URI</filename> variable to locate
|
|
the source code and any local patch files from other
|
|
developers are located.
|
|
The result is that the command sets up the source
|
|
code, the new version of the recipe, and an append file
|
|
all within the workspace.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Resolve any Conflicts created by the Upgrade</emphasis>:
|
|
At this point, there could be some conflicts due to the
|
|
software being upgraded to a new version.
|
|
This would occur if your recipe specifies some patch files in
|
|
<filename>SRC_URI</filename> that conflict with changes
|
|
made in the new version of the software.
|
|
If this is the case, you need to resolve the conflicts
|
|
by editing the source and following the normal
|
|
<filename>git rebase</filename> conflict resolution
|
|
process.</para>
|
|
|
|
<para>Before moving onto the next step, be sure to resolve any
|
|
such conflicts created through use of a newer or different
|
|
version of the software.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Build the Recipe</emphasis>:
|
|
Once you have your recipe in order, you can build it.
|
|
You can either use <filename>devtool build</filename> or
|
|
<filename>bitbake</filename>.
|
|
Either method produces build output that is stored
|
|
in
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-TMPDIR'><filename>TMPDIR</filename></ulink>.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Deploy the Build Output</emphasis>:
|
|
When you use the <filename>devtool build</filename>
|
|
command or <filename>bitbake</filename> to build out your
|
|
recipe, you probably want to see if the resulting build
|
|
output works as expected on target hardware.
|
|
<note>
|
|
This step assumes you have a previously built
|
|
image that is already either running in QEMU or
|
|
running on actual hardware.
|
|
Also, it is assumed that for deployment of the image
|
|
to the target, SSH is installed in the image and if
|
|
the image is running on real hardware that you have
|
|
network access to and from your development machine.
|
|
</note>
|
|
You can deploy your build output to that target hardware by
|
|
using the <filename>devtool deploy-target</filename> command:
|
|
<literallayout class='monospaced'>
|
|
$ devtool deploy-target <replaceable>recipe target</replaceable>
|
|
</literallayout>
|
|
The <replaceable>target</replaceable> is a live target machine
|
|
running as an SSH server.</para>
|
|
|
|
<para>You can, of course, also deploy the image you build
|
|
using the <filename>devtool build-image</filename> command
|
|
to actual hardware.
|
|
However, <filename>devtool</filename> does not provide a
|
|
specific command that allows you to do this.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
<emphasis>Finish Your Work With the Recipe</emphasis>:
|
|
The <filename>devtool finish</filename> command creates
|
|
any patches corresponding to commits in the local
|
|
Git repository, moves the new recipe to a more permanent
|
|
layer, and then resets the recipe so that the recipe is
|
|
built normally rather than from the workspace.
|
|
If you specify a destination layer that is the same as
|
|
the original source, then the old version of the
|
|
recipe and associated files will be removed prior to
|
|
adding the new version.
|
|
<literallayout class='monospaced'>
|
|
$ devtool finish <replaceable>recipe layer</replaceable>
|
|
</literallayout>
|
|
<note>
|
|
Any changes you want to turn into patches must be
|
|
committed to the Git repository in the source tree.
|
|
</note></para>
|
|
<para>As a final process of the
|
|
<filename>devtool finish</filename> command, the state
|
|
of the standard layers and the upstream source is
|
|
restored so that you can build the recipe from those
|
|
areas rather than the workspace.
|
|
<note>
|
|
You can use the <filename>devtool reset</filename>
|
|
command to put things back should you decide you
|
|
do not want to proceed with your work.
|
|
If you do use this command, realize that the source
|
|
tree is preserved.
|
|
</note>
|
|
</para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="using-a-quilt-workflow">
|
|
<title>Using Quilt in Your Workflow</title>
|
|
|
|
<para>
|
|
<ulink url='http://savannah.nongnu.org/projects/quilt'>Quilt</ulink>
|
|
is a powerful tool that allows you to capture source code changes
|
|
without having a clean source tree.
|
|
This section outlines the typical workflow you can use to modify
|
|
source code, test changes, and then preserve the changes in the
|
|
form of a patch all using Quilt.
|
|
<note><title>Tip</title>
|
|
With regard to preserving changes to source files if you
|
|
clean a recipe or have <filename>rm_work</filename> enabled,
|
|
the workflow described in the
|
|
"<link linkend='using-devtool-in-your-workflow'>Using <filename>devtool</filename> in Your Workflow</link>"
|
|
section is a safer development flow than than the flow that
|
|
uses Quilt.
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
Follow these general steps:
|
|
<orderedlist>
|
|
<listitem><para><emphasis>Find the Source Code:</emphasis>
|
|
Temporary source code used by the OpenEmbedded build system
|
|
is kept in the
|
|
<link linkend='build-directory'>Build Directory</link>.
|
|
See the
|
|
"<link linkend='finding-the-temporary-source-code'>Finding Temporary Source Code</link>"
|
|
section to learn how to locate the directory that has the
|
|
temporary source code for a particular package.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Change Your Working Directory:</emphasis>
|
|
You need to be in the directory that has the temporary source code.
|
|
That directory is defined by the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-S'><filename>S</filename></ulink>
|
|
variable.</para></listitem>
|
|
<listitem><para><emphasis>Create a New Patch:</emphasis>
|
|
Before modifying source code, you need to create a new patch.
|
|
To create a new patch file, use <filename>quilt new</filename> as below:
|
|
<literallayout class='monospaced'>
|
|
$ quilt new my_changes.patch
|
|
</literallayout></para></listitem>
|
|
<listitem><para><emphasis>Notify Quilt and Add Files:</emphasis>
|
|
After creating the patch, you need to notify Quilt about the files
|
|
you plan to edit.
|
|
You notify Quilt by adding the files to the patch you just created:
|
|
<literallayout class='monospaced'>
|
|
$ quilt add file1.c file2.c file3.c
|
|
</literallayout>
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Edit the Files:</emphasis>
|
|
Make your changes in the source code to the files you added
|
|
to the patch.
|
|
</para></listitem>
|
|
<listitem><para><emphasis>Test Your Changes:</emphasis>
|
|
Once you have modified the source code, the easiest way to
|
|
your changes is by calling the
|
|
<filename>do_compile</filename> task as shown in the
|
|
following example:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -c compile -f <replaceable>package</replaceable>
|
|
</literallayout>
|
|
The <filename>-f</filename> or <filename>--force</filename>
|
|
option forces the specified task to execute.
|
|
If you find problems with your code, you can just keep editing and
|
|
re-testing iteratively until things work as expected.
|
|
<note>All the modifications you make to the temporary source code
|
|
disappear once you run the
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-clean'><filename>do_clean</filename></ulink>
|
|
or
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-cleanall'><filename>do_cleanall</filename></ulink>
|
|
tasks using BitBake (i.e.
|
|
<filename>bitbake -c clean <replaceable>package</replaceable></filename>
|
|
and
|
|
<filename>bitbake -c cleanall <replaceable>package</replaceable></filename>).
|
|
Modifications will also disappear if you use the <filename>rm_work</filename>
|
|
feature as described in the
|
|
"<ulink url='&YOCTO_DOCS_QS_URL;#qs-building-images'>Building Images</ulink>"
|
|
section of the Yocto Project Quick Start.
|
|
</note></para></listitem>
|
|
<listitem><para><emphasis>Generate the Patch:</emphasis>
|
|
Once your changes work as expected, you need to use Quilt to generate the final patch that
|
|
contains all your modifications.
|
|
<literallayout class='monospaced'>
|
|
$ quilt refresh
|
|
</literallayout>
|
|
At this point, the <filename>my_changes.patch</filename> file has all your edits made
|
|
to the <filename>file1.c</filename>, <filename>file2.c</filename>, and
|
|
<filename>file3.c</filename> files.</para>
|
|
<para>You can find the resulting patch file in the <filename>patches/</filename>
|
|
subdirectory of the source (<filename>S</filename>) directory.</para></listitem>
|
|
<listitem><para><emphasis>Copy the Patch File:</emphasis>
|
|
For simplicity, copy the patch file into a directory named <filename>files</filename>,
|
|
which you can create in the same directory that holds the recipe
|
|
(<filename>.bb</filename>) file or the
|
|
append (<filename>.bbappend</filename>) file.
|
|
Placing the patch here guarantees that the OpenEmbedded build system will find
|
|
the patch.
|
|
Next, add the patch into the
|
|
<filename><ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'>SRC_URI</ulink></filename>
|
|
of the recipe.
|
|
Here is an example:
|
|
<literallayout class='monospaced'>
|
|
SRC_URI += "file://my_changes.patch"
|
|
</literallayout></para></listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id='finding-the-temporary-source-code'>
|
|
<title>Finding Temporary Source Code</title>
|
|
|
|
<para>
|
|
You might find it helpful during development to modify the
|
|
temporary source code used by recipes to build packages.
|
|
For example, suppose you are developing a patch and you need to
|
|
experiment a bit to figure out your solution.
|
|
After you have initially built the package, you can iteratively
|
|
tweak the source code, which is located in the
|
|
<link linkend='build-directory'>Build Directory</link>, and then
|
|
you can force a re-compile and quickly test your altered code.
|
|
Once you settle on a solution, you can then preserve your changes
|
|
in the form of patches.
|
|
If you are using Quilt for development, see the
|
|
"<link linkend='using-a-quilt-workflow'>Using Quilt in Your Workflow</link>"
|
|
section for more information.
|
|
</para>
|
|
|
|
<para>
|
|
During a build, the unpacked temporary source code used by recipes
|
|
to build packages is available in the Build Directory as
|
|
defined by the
|
|
<filename><ulink url='&YOCTO_DOCS_REF_URL;#var-S'>S</ulink></filename> variable.
|
|
Below is the default value for the <filename>S</filename> variable as defined in the
|
|
<filename>meta/conf/bitbake.conf</filename> configuration file in the
|
|
<link linkend='source-directory'>Source Directory</link>:
|
|
<literallayout class='monospaced'>
|
|
S = "${WORKDIR}/${BP}"
|
|
</literallayout>
|
|
You should be aware that many recipes override the <filename>S</filename> variable.
|
|
For example, recipes that fetch their source from Git usually set
|
|
<filename>S</filename> to <filename>${WORKDIR}/git</filename>.
|
|
<note>
|
|
The
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-BP'><filename>BP</filename></ulink>
|
|
represents the base recipe name, which consists of the name and version:
|
|
<literallayout class='monospaced'>
|
|
BP = "${BPN}-${PV}"
|
|
</literallayout>
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
The path to the work directory for the recipe
|
|
(<ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink>)
|
|
is defined as follows:
|
|
<literallayout class='monospaced'>
|
|
${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}
|
|
</literallayout>
|
|
The actual directory depends on several things:
|
|
<itemizedlist>
|
|
<listitem><ulink url='&YOCTO_DOCS_REF_URL;#var-TMPDIR'><filename>TMPDIR</filename></ulink>:
|
|
The top-level build output directory</listitem>
|
|
<listitem><ulink url='&YOCTO_DOCS_REF_URL;#var-MULTIMACH_TARGET_SYS'><filename>MULTIMACH_TARGET_SYS</filename></ulink>:
|
|
The target system identifier</listitem>
|
|
<listitem><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink>:
|
|
The recipe name</listitem>
|
|
<listitem><ulink url='&YOCTO_DOCS_REF_URL;#var-EXTENDPE'><filename>EXTENDPE</filename></ulink>:
|
|
The epoch - (if
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-PE'><filename>PE</filename></ulink>
|
|
is not specified, which is usually the case for most
|
|
recipes, then <filename>EXTENDPE</filename> is blank)</listitem>
|
|
<listitem><ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>:
|
|
The recipe version</listitem>
|
|
<listitem><ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>:
|
|
The recipe revision</listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
As an example, assume a Source Directory top-level folder
|
|
named <filename>poky</filename>, a default Build Directory at
|
|
<filename>poky/build</filename>, and a
|
|
<filename>qemux86-poky-linux</filename> machine target
|
|
system.
|
|
Furthermore, suppose your recipe is named
|
|
<filename>foo_1.3.0.bb</filename>.
|
|
In this case, the work directory the build system uses to
|
|
build the package would be as follows:
|
|
<literallayout class='monospaced'>
|
|
poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
Now that you know where to locate the directory that has the
|
|
temporary source code, you can use a Quilt as described in section
|
|
"<link linkend='using-a-quilt-workflow'>Using Quilt in Your Workflow</link>"
|
|
to make your edits, test the changes, and preserve the changes in
|
|
the form of patches.
|
|
</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id='image-development-using-toaster'>
|
|
<title>Image Development Using Toaster</title>
|
|
|
|
<para>
|
|
Toaster is a web interface to the Yocto Project's OpenEmbedded build
|
|
system.
|
|
You can initiate builds using Toaster as well as examine the results
|
|
and statistics of builds.
|
|
See the
|
|
<ulink url='&YOCTO_DOCS_TOAST_URL;#toaster-manual-intro'>Toaster User Manual</ulink>
|
|
for information on how to set up and use Toaster to build images.
|
|
</para>
|
|
</section>
|
|
|
|
<section id="platdev-appdev-devshell">
|
|
<title>Using a Development Shell</title>
|
|
|
|
<para>
|
|
When debugging certain commands or even when just editing packages,
|
|
<filename>devshell</filename> can be a useful tool.
|
|
When you invoke <filename>devshell</filename>, all tasks up to and
|
|
including
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-patch'><filename>do_patch</filename></ulink>
|
|
are run for the specified target.
|
|
Then, a new terminal is opened and you are placed in
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-S'><filename>S</filename></ulink><filename>}</filename>,
|
|
the source directory.
|
|
In the new terminal, all the OpenEmbedded build-related environment variables are
|
|
still defined so you can use commands such as <filename>configure</filename> and
|
|
<filename>make</filename>.
|
|
The commands execute just as if the OpenEmbedded build system were executing them.
|
|
Consequently, working this way can be helpful when debugging a build or preparing
|
|
software to be used with the OpenEmbedded build system.
|
|
</para>
|
|
|
|
<para>
|
|
Following is an example that uses <filename>devshell</filename> on a target named
|
|
<filename>matchbox-desktop</filename>:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake matchbox-desktop -c devshell
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
This command spawns a terminal with a shell prompt within the OpenEmbedded build environment.
|
|
The <ulink url='&YOCTO_DOCS_REF_URL;#var-OE_TERMINAL'><filename>OE_TERMINAL</filename></ulink>
|
|
variable controls what type of shell is opened.
|
|
</para>
|
|
|
|
<para>
|
|
For spawned terminals, the following occurs:
|
|
<itemizedlist>
|
|
<listitem><para>The <filename>PATH</filename> variable includes the
|
|
cross-toolchain.</para></listitem>
|
|
<listitem><para>The <filename>pkgconfig</filename> variables find the correct
|
|
<filename>.pc</filename> files.</para></listitem>
|
|
<listitem><para>The <filename>configure</filename> command finds the
|
|
Yocto Project site files as well as any other necessary files.</para></listitem>
|
|
</itemizedlist>
|
|
</para>
|
|
|
|
<para>
|
|
Within this environment, you can run configure or compile
|
|
commands as if they were being run by
|
|
the OpenEmbedded build system itself.
|
|
As noted earlier, the working directory also automatically changes to the
|
|
Source Directory (<ulink url='&YOCTO_DOCS_REF_URL;#var-S'><filename>S</filename></ulink>).
|
|
</para>
|
|
|
|
<para>
|
|
To manually run a specific task using <filename>devshell</filename>,
|
|
run the corresponding <filename>run.*</filename> script in
|
|
the
|
|
<filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-WORKDIR'><filename>WORKDIR</filename></ulink><filename>}/temp</filename>
|
|
directory (e.g.,
|
|
<filename>run.do_configure.</filename><replaceable>pid</replaceable>).
|
|
If a task's script does not exist, which would be the case if the task was
|
|
skipped by way of the sstate cache, you can create the task by first running
|
|
it outside of the <filename>devshell</filename>:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake -c <replaceable>task</replaceable>
|
|
</literallayout>
|
|
<note><title>Notes</title>
|
|
<itemizedlist>
|
|
<listitem><para>Execution of a task's <filename>run.*</filename>
|
|
script and BitBake's execution of a task are identical.
|
|
In other words, running the script re-runs the task
|
|
just as it would be run using the
|
|
<filename>bitbake -c</filename> command.
|
|
</para></listitem>
|
|
<listitem><para>Any <filename>run.*</filename> file that does not
|
|
have a <filename>.pid</filename> extension is a
|
|
symbolic link (symlink) to the most recent version of that
|
|
file.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</note>
|
|
</para>
|
|
|
|
<para>
|
|
Remember, that the <filename>devshell</filename> is a mechanism that allows
|
|
you to get into the BitBake task execution environment.
|
|
And as such, all commands must be called just as BitBake would call them.
|
|
That means you need to provide the appropriate options for
|
|
cross-compilation and so forth as applicable.
|
|
</para>
|
|
|
|
<para>
|
|
When you are finished using <filename>devshell</filename>, exit the shell
|
|
or close the terminal window.
|
|
</para>
|
|
|
|
<note><title>Notes</title>
|
|
<itemizedlist>
|
|
<listitem><para>
|
|
It is worth remembering that when using <filename>devshell</filename>
|
|
you need to use the full compiler name such as <filename>arm-poky-linux-gnueabi-gcc</filename>
|
|
instead of just using <filename>gcc</filename>.
|
|
The same applies to other applications such as <filename>binutils</filename>,
|
|
<filename>libtool</filename> and so forth.
|
|
BitBake sets up environment variables such as <filename>CC</filename>
|
|
to assist applications, such as <filename>make</filename> to find the correct tools.
|
|
</para></listitem>
|
|
<listitem><para>
|
|
It is also worth noting that <filename>devshell</filename> still works over
|
|
X11 forwarding and similar situations.
|
|
</para></listitem>
|
|
</itemizedlist>
|
|
</note>
|
|
</section>
|
|
|
|
<section id="platdev-appdev-devpyshell">
|
|
<title>Using a Development Python Shell</title>
|
|
|
|
<para>
|
|
Similar to working within a development shell as described in
|
|
the previous section, you can also spawn and work within an
|
|
interactive Python development shell.
|
|
When debugging certain commands or even when just editing packages,
|
|
<filename>devpyshell</filename> can be a useful tool.
|
|
When you invoke <filename>devpyshell</filename>, all tasks up to and
|
|
including
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-patch'><filename>do_patch</filename></ulink>
|
|
are run for the specified target.
|
|
Then a new terminal is opened.
|
|
Additionally, key Python objects and code are available in the same
|
|
way they are to BitBake tasks, in particular, the data store 'd'.
|
|
So, commands such as the following are useful when exploring the data
|
|
store and running functions:
|
|
<literallayout class='monospaced'>
|
|
pydevshell> d.getVar("STAGING_DIR", True)
|
|
'/media/build1/poky/build/tmp/sysroots'
|
|
pydevshell> d.getVar("STAGING_DIR", False)
|
|
'${TMPDIR}/sysroots'
|
|
pydevshell> d.setVar("FOO", "bar")
|
|
pydevshell> d.getVar("FOO", True)
|
|
'bar'
|
|
pydevshell> d.delVar("FOO")
|
|
pydevshell> d.getVar("FOO", True)
|
|
pydevshell> bb.build.exec_func("do_unpack", d)
|
|
pydevshell>
|
|
</literallayout>
|
|
The commands execute just as if the OpenEmbedded build system were executing them.
|
|
Consequently, working this way can be helpful when debugging a build or preparing
|
|
software to be used with the OpenEmbedded build system.
|
|
</para>
|
|
|
|
<para>
|
|
Following is an example that uses <filename>devpyshell</filename> on a target named
|
|
<filename>matchbox-desktop</filename>:
|
|
<literallayout class='monospaced'>
|
|
$ bitbake matchbox-desktop -c devpyshell
|
|
</literallayout>
|
|
</para>
|
|
|
|
<para>
|
|
This command spawns a terminal and places you in an interactive
|
|
Python interpreter within the OpenEmbedded build environment.
|
|
The <ulink url='&YOCTO_DOCS_REF_URL;#var-OE_TERMINAL'><filename>OE_TERMINAL</filename></ulink>
|
|
variable controls what type of shell is opened.
|
|
</para>
|
|
|
|
<para>
|
|
When you are finished using <filename>devpyshell</filename>, you
|
|
can exit the shell either by using Ctrl+d or closing the terminal
|
|
window.
|
|
</para>
|
|
</section>
|
|
|
|
</chapter>
|