path: root/documentation/sdk-manual/sdk-extensible.xml

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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

<chapter id='sdk-extensible'>

<title>Using the Extensible SDK</title>

<para>
    This chapter describes the extensible SDK and how to use it.
    The extensible SDK makes it easy to add new applications and libraries
    to an image, modify the source for an existing component, test
    changes on the target hardware, and ease integration into the rest
    of the build system.
</para>

<para>
    Information in this chapter covers features that are not part of the
    standard SDK.
    In other words, the chapter presents information unique to the
    extensible SDK only.
    For information on how to use the standard SDK, see the
    "<link linkend='sdk-using-the-standard-sdk'>Using the Standard SDK</link>"
    chapter.
</para>

<section id='sdk-setting-up-to-use-the-extensible-sdk'>
    <title>Setting Up to Use the Extensible SDK</title>

    <para>
        Getting set up to use the extensible SDK is identical to getting set
        up to use the standard SDK.
        You still need to locate and run the installer and then run the
        environment setup script.
        See the
        "<link linkend='sdk-installing-the-sdk'>Installing the SDK</link>"
        and the
        "<link linkend='sdk-running-the-sdk-environment-setup-script'>Running the SDK Environment Setup Script</link>"
        sections for general information.
        The following items highlight the only differences between getting
        set up to use the extensible SDK as compared to the standard SDK:
        <itemizedlist>
            <listitem><para><emphasis>Default Installation Directory:</emphasis>
                By default, the extensible SDK installs into the
                <filename>poky_sdk</filename> folder of your home directory.
                As with the standard SDK, you can choose to install the
                extensible SDK in any location when you run the installer.
                </para></listitem>
            <listitem><para><emphasis>Build Tools and Build System:</emphasis>
                The extensible SDK installer performs additional tasks as
                compared to the standard SDK installer.
                The extensible SDK installer extracts build tools specific
                to the SDK and the installer also prepares the build system.
                Here is example output for running the extensible SDK
                installer:
                <literallayout class='monospaced'>
     $ ./poky-glibc-x86_64-core-image-minimal-core2-64-toolchain-ext-2.1+snapshot.sh
     Poky (Yocto Project Reference Distro) Extensible SDK installer version 2.1+snapshot
     ===================================================================================
     Enter target directory for SDK (default: ~/poky_sdk):
     You are about to install the SDK to "/home/scottrif/poky_sdk". Proceed[Y/n]? Y
     Extracting SDK......................................................................done
     Setting it up...
     Extracting buildtools...
     Preparing build system...
     done
     SDK has been successfully set up and is ready to be used.
     Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
      $ . /home/scottrif/poky_sdk/environment-setup-core2-64-poky-linux
                </literallayout>
                </para></listitem>
        </itemizedlist>
    </para>

    <para>
        After installing the SDK, you need to run the SDK environment setup
        script.
        Here is the output:
        <literallayout class='monospaced'>
     $ source environment-setup-core2-64-poky-linux
     SDK environment now set up; additionally you may now run devtool to perform development tasks.
     Run devtool --help for further details.
        </literallayout>
        Once you run the environment setup script, you have
        <filename>devtool</filename> available.
    </para>
</section>

<section id='sdk-use-devtool-to-add-an-application'>
    <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/sdk-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.
                        As always, if required <filename>devtool</filename> 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>:
                <note>
                    You could use <filename>bitbake</filename> to build
                    the recipe as well.
                </note>
                <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>Optionally Update the Recipe With Patch Files</emphasis>:
                Once you are satisfied with the recipe, if you have made
                any changes to the source tree that you want to have
                applied by the recipe, you need to generate patches
                from those changes.
                You do this before moving the recipe
                to its final layer and cleaning up the workspace area
                <filename>devtool</filename> uses.
                This optional step is especially relevant if you are
                using or adding third-party software.</para>
                <para>To convert commits created using Git to patch files,
                use the <filename>devtool update-recipe</filename> command.
                <note>
                    Any changes you want to turn into patches must be
                    committed to the Git repository in the source tree.
                </note>
                <literallayout class='monospaced'>
     $ devtool update-recipe <replaceable>recipe</replaceable>
                </literallayout>
                </para></listitem>
            <listitem><para><emphasis>Move the Recipe to its Permanent Layer</emphasis>:
                Before cleaning up the workspace, you need to move the
                final recipe to its permanent layer.
                You must do this before using the
                <filename>devtool reset</filename> command if you want to
                retain the recipe.
                </para></listitem>
            <listitem><para><emphasis>Reset the Recipe</emphasis>:
                As a final step, you can restore the state such that
                standard layers and the upstream source is used to build
                the recipe rather than data in the workspace.
                To reset the recipe, use the <filename>devtool reset</filename>
                command:
                <literallayout class='monospaced'>
     $ devtool reset <replaceable>recipe</replaceable>
                </literallayout>
                </para></listitem>
        </orderedlist>
    </para>
</section>

<section id='sdk-devtool-use-devtool-modify-to-modify-the-source-of-an-existing-component'>
    <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/sdk-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.
                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>Optionally Create Patch Files for Your Changes</emphasis>:
                After you have debugged your changes, you can
                use <filename>devtool update-recipe</filename> to
                generate patch files for all the commits you have
                made.
                <note>
                    Patch files are generated only for changes
                    you have committed.
                </note>
                <literallayout class='monospaced'>
     $ devtool update-recipe <replaceable>recipe</replaceable>
                </literallayout>
                By default, the
                <filename>devtool update-recipe</filename> command
                creates the patch files in a folder named the same
                as the recipe beneath the folder in which the recipe
                resides, and updates the recipe's
                <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>
                statement to point to the generated patch files.
                <note>
                    You can use the
                    "--append <replaceable>LAYERDIR</replaceable>"
                    option to cause the command to create append files
                    in a specific layer rather than the default
                    recipe layer.
                </note>
                </para></listitem>
            <listitem><para><emphasis>Restore the Workspace</emphasis>:
                The <filename>devtool reset</filename> restores the
                state so that standard layers and upstream sources are
                used to build the recipe rather than what is in the
                workspace.
                <literallayout class='monospaced'>
     $ devtool reset <replaceable>recipe</replaceable>
                </literallayout>
                </para></listitem>
        </orderedlist>
    </para>
</section>

<section id='sdk-using-the-extensible-sdk-to-task-2'>
    <title>Using the Extensible SDK to <replaceable>item-2</replaceable></title>

    <para role='writernotes'>
        Describe the specific task you are going to accomplish with the
        extensible SDK.
        Provide a diagram showing the rough flow of the task.
        Provide specific steps using a real example that works through the
        task.
    </para>
</section>

<section id='sdk-using-the-extensible-sdk-to-task-3'>
    <title>Using the Extensible SDK to <replaceable>item-3</replaceable></title>

    <para role='writernotes'>
        Describe the specific task you are going to accomplish with the
        extensible SDK.
        Provide a diagram showing the rough flow of the task.
        Provide specific steps using a real example that works through the
        task.
    </para>
</section>

<section id='sdk-using-the-extensible-sdk-to-task-x'>
    <title>Using the Extensible SDK to <replaceable>item-x</replaceable></title>

    <para role='writernotes'>
        Describe the specific task you are going to accomplish with the
        extensible SDK.
        Provide a diagram showing the rough flow of the task.
        Provide specific steps using a real example that works through the
        task.
    </para>
</section>

</chapter>
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