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diff --git a/import-layers/yocto-poky/documentation/sdk-manual/sdk-extensible.xml b/import-layers/yocto-poky/documentation/sdk-manual/sdk-extensible.xml new file mode 100644 index 000000000..3e11fc97d --- /dev/null +++ b/import-layers/yocto-poky/documentation/sdk-manual/sdk-extensible.xml @@ -0,0 +1,1304 @@ +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" +"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" +[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] > + +<chapter id='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 + <ulink url='&YOCTO_DOCS_DEV_URL;#build-system-term'>OpenEmbedded build system</ulink>. +</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. + However, unlike the standard SDK, the location you choose needs + to be writable for whichever users need to use the SDK, + since files will need to be written under that directory during + the normal course of operation. + </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 internal build + system within the SDK. + 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='using-devtool-in-your-sdk-workflow'> + <title>Using <filename>devtool</filename> in Your SDK Workflow</title> + + <para> + The cornerstone of the extensible SDK is a command-line tool + called <filename>devtool</filename>. + This tool provides a number of features that help + you build, test and package software within the extensible SDK, and + optionally integrate it into an image built by the OpenEmbedded build + system. + </para> + + <para> + The <filename>devtool</filename> command line is organized similarly + to + <ulink url='&YOCTO_DOCS_DEV_URL;#git'>Git</ulink> in that it has a + number of sub-commands for each function. + You can run <filename>devtool --help</filename> to see all the + commands. + </para> + + <para> + Two <filename>devtool</filename> subcommands that provide + entry-points into development are: + <itemizedlist> + <listitem><para><emphasis><filename>devtool add</filename></emphasis>: + Assists in adding new software to be built. + </para></listitem> + <listitem><para><emphasis><filename>devtool modify</filename></emphasis>: + Sets up an environment to enable you to modify the source of + an existing component. + </para></listitem> + </itemizedlist> + As with the OpenEmbedded build system, "recipes" represent software + packages within <filename>devtool</filename>. + When you use <filename>devtool add</filename>, a recipe is + automatically created. + When you use <filename>devtool modify</filename>, the specified + existing recipe is used in order to determine where to get the source + code and how to patch it. + In both cases, an environment is set up so that when you build the + recipe a source tree that is under your control is used in order to + allow you to make changes to the source as desired. + By default, both new recipes and the source go into a "workspace" + directory under the SDK. + </para> + + <para> + The remainder of this section presents the + <filename>devtool add</filename> and + <filename>devtool modify</filename> workflows. + </para> + + <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>: + <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. + </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 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> + +<section id='sdk-a-closer-look-at-devtool-add'> + <title>A Closer Look at <filename>devtool add</filename></title> + + <para> + The <filename>devtool add</filename> command automatically creates a + recipe based on the source tree with which you provide it. + Currently, the command has support for the following: + <itemizedlist> + <listitem><para> + Autotools (<filename>autoconf</filename> and + <filename>automake</filename>) + </para></listitem> + <listitem><para> + CMake + </para></listitem> + <listitem><para> + Scons + </para></listitem> + <listitem><para> + <filename>qmake</filename> + </para></listitem> + <listitem><para> + Plain <filename>Makefile</filename> + </para></listitem> + <listitem><para> + Out-of-tree kernel module + </para></listitem> + <listitem><para> + Binary package (i.e. "-b" option) + </para></listitem> + <listitem><para> + Node.js module through + <filename>npm</filename> + </para></listitem> + <listitem><para> + Python modules that use <filename>setuptools</filename> + or <filename>distutils</filename> + </para></listitem> + </itemizedlist> + </para> + + <para> + Apart from binary packages, the determination of how a source tree + should be treated is automatic based on the files present within + that source tree. + For example, if a <filename>CMakeLists.txt</filename> file is found, + then the source tree is assumed to be using + CMake and is treated accordingly. + <note> + In most cases, you need to edit the automatically generated + recipe in order to make it build properly. + Typically, you would go through several edit and build cycles + until you can build the recipe. + Once the recipe can be built, you could use possible further + iterations to test the recipe on the target device. + </note> + </para> + + <para> + The remainder of this section covers specifics regarding how parts + of the recipe are generated. + </para> + + <section id='sdk-name-and-version'> + <title>Name and Version</title> + + <para> + If you do not specify a name and version on the command + line, <filename>devtool add</filename> attempts to determine + the name and version of the software being built from + various metadata within the source tree. + Furthermore, the command sets the name of the created recipe + file accordingly. + If the name or version cannot be determined, the + <filename>devtool add</filename> command prints an error and + you must re-run the command with both the name and version + or just the name or version specified. + </para> + + <para> + Sometimes the name or version determined from the source tree + might be incorrect. + For such a case, you must reset the recipe: + <literallayout class='monospaced'> + $ devtool reset -n <replaceable>recipename</replaceable> + </literallayout> + After running the <filename>devtool reset</filename> command, + you need to run <filename>devtool add</filename> again and + provide the name or the version. + </para> + </section> + + <section id='sdk-dependency-detection-and-mapping'> + <title>Dependency Detection and Mapping</title> + + <para> + The <filename>devtool add</filename> command attempts to + detect build-time dependencies and map them to other recipes + in the system. + During this mapping, the command fills in the names of those + recipes in the + <ulink url='&YOCTO_DOCS_REF_URL;#var-DEPENDS'><filename>DEPENDS</filename></ulink> + value within the recipe. + If a dependency cannot be mapped, then a comment is placed in + the recipe indicating such. + The inability to map a dependency might be caused because the + naming is not recognized or because the dependency simply is + not available. + For cases where the dependency is not available, you must use + the <filename>devtool add</filename> command to add an + additional recipe to satisfy the dependency and then come + back to the first recipe and add its name to + <filename>DEPENDS</filename>. + </para> + + <para> + If you need to add runtime dependencies, you can do so by + adding the following to your recipe: + <literallayout class='monospaced'> + RDEPENDS_${PN} += "dependency1 dependency2 ..." + </literallayout> + <note> + The <filename>devtool add</filename> command often cannot + distinguish between mandatory and optional dependencies. + Consequently, some of the detected dependencies might + in fact be optional. + When in doubt, consult the documentation or the configure + script for the software the recipe is building for further + details. + In some cases, you might find you can substitute the + dependency for an option to disable the associated + functionality passed to the configure script. + </note> + </para> + </section> + + <section id='sdk-license-detection'> + <title>License Detection</title> + + <para> + The <filename>devtool add</filename> command attempts to + determine if the software you are adding is able to be + distributed under a common open-source license and sets the + <ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE</filename></ulink> + value accordingly. + You should double-check this value against the documentation + or source files for the software you are building and update + that <filename>LICENSE</filename> value if necessary. + </para> + + <para> + The <filename>devtool add</filename> command also sets the + <ulink url='&YOCTO_DOCS_REF_URL;#var-LIC_FILES_CHKSUM'><filename>LIC_FILES_CHKSUM</filename></ulink> + value to point to all files that appear to be license-related. + However, license statements often appear in comments at the top + of source files or within documentation. + Consequently, you might need to amend the + <filename>LIC_FILES_CHKSUM</filename> variable to point to one + or more of those comments if present. + Setting <filename>LIC_FILES_CHKSUM</filename> is particularly + important for third-party software. + The mechanism attempts to ensure correct licensing should you + upgrade the recipe to a newer upstream version in future. + Any change in licensing is detected and you receive an error + prompting you to check the license text again. + </para> + + <para> + If the <filename>devtool add</filename> command cannot + determine licensing information, the + <filename>LICENSE</filename> value is set to "CLOSED" and the + <filename>LIC_FILES_CHKSUM</filename> vaule remains unset. + This behavior allows you to continue with development but is + unlikely to be correct in all cases. + Consequently, you should check the documentation or source + files for the software you are building to determine the actual + license. + </para> + </section> + + <section id='sdk-adding-makefile-only-software'> + <title>Adding Makefile-Only Software</title> + + <para> + The use of <filename>make</filename> by itself is very common + in both proprietary and open source software. + Unfortunately, Makefiles are often not written with + cross-compilation in mind. + Thus, <filename>devtool add</filename> often cannot do very + much to ensure that these Makefiles build correctly. + It is very common, for example, to explicitly call + <filename>gcc</filename> instead of using the + <filename>CC</filename> variable. + Usually, in a cross-compilation environment, + <filename>gcc</filename> is the compiler for the build host + and the cross-compiler is named something similar to + <filename>arm-poky-linux-gnueabi-gcc</filename> and might + require some arguments (e.g. to point to the associated sysroot + for the target machine). + </para> + + <para> + When writing a recipe for Makefile-only software, keep the + following in mind: + <itemizedlist> + <listitem><para> + You probably need to patch the Makefile to use + variables instead of hardcoding tools within the + toolchain such as <filename>gcc</filename> and + <filename>g++</filename>. + </para></listitem> + <listitem><para> + The environment in which <filename>make</filename> runs + is set up with various standard variables for + compilation (e.g. <filename>CC</filename>, + <filename>CXX</filename>, and so forth) in a similar + manner to the environment set up by the SDK's + environment setup script. + One easy way to see these variables is to run the + <filename>devtool build</filename> command on the + recipe and then look in + <filename>oe-logs/run.do_compile</filename>. + Towards the top of this file you will see a list of + environment variables that are being set. + You can take advantage of these variables within the + Makefile. + </para></listitem> + <listitem><para> + If the Makefile sets a default for a variable using "=", + that default overrides the value set in the environment, + which is usually not desirable. + In this situation, you can either patch the Makefile + so it sets the default using the "?=" operator, or + you can alternatively force the value on the + <filename>make</filename> command line. + To force the value on the command line, add the + variable setting to + <ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OEMAKE'><filename>EXTRA_OEMAKE</filename></ulink> + within the recipe as follows: + <literallayout class='monospaced'> + EXTRA_OEMAKE += "'CC=${CC}' 'CXX=${CXX}'" + </literallayout> + In the above example, single quotes are used around the + variable settings as the values are likely to contain + spaces because required default options are passed to + the compiler. + </para></listitem> + <listitem><para> + Hardcoding paths inside Makefiles is often problematic + in a cross-compilation environment. + This is particularly true because those hardcoded paths + often point to locations on the build host and thus + will either be read-only or will introduce + contamination into the cross-compilation by virtue of + being specific to the build host rather than the target. + Patching the Makefile to use prefix variables or other + path variables is usually the way to handle this. + </para></listitem> + <listitem><para> + Sometimes a Makefile runs target-specific commands such + as <filename>ldconfig</filename>. + For such cases, you might be able to simply apply + patches that remove these commands from the Makefile. + </para></listitem> + </itemizedlist> + </para> + </section> + + <section id='sdk-adding-native-tools'> + <title>Adding Native Tools</title> + + <para> + Often, you need to build additional tools that run on the + build host system as opposed to the target. + You should indicate this using one of the following methods + when you run <filename>devtool add</filename>: + <itemizedlist> + <listitem><para> + Specify the name of the recipe such that it ends + with "-native". + Specifying the name like this produces a recipe that + only builds for the build host. + </para></listitem> + <listitem><para> + Specify the "‐‐also-native" option with the + <filename>devtool add</filename> command. + Specifying this option creates a recipe file that still + builds for the target but also creates a variant with + a "-native" suffix that builds for the build host. + </para></listitem> + </itemizedlist> + <note> + If you need to add a tool that is shipped as part of a + source tree that builds code for the target, you can + typically accomplish this by building the native and target + parts separately rather than within the same compilation + process. + Realize though that with the "‐‐also-native" option, you + can add the tool using just one recipe file. + </note> + </para> + </section> + + <section id='sdk-adding-node-js-modules'> + <title>Adding Node.js Modules</title> + + <para> + You can use the <filename>devtool add</filename> command in the + following form to add Node.js modules: + <literallayout class='monospaced'> + $ devtool add "npm://registry.npmjs.org;name=forever;version=0.15.1" + </literallayout> + The name and version parameters are mandatory. + Lockdown and shrinkwrap files are generated and pointed to by + the recipe in order to freeze the version that is fetched for + the dependencies according to the first time. + This also saves checksums that are verified on future fetches. + Together, these behaviors ensure the reproducibility and + integrity of the build. + <note><title>Notes</title> + <itemizedlist> + <listitem><para> + You must use quotes around the URL. + The <filename>devtool add</filename> does not require + the quotes, but the shell considers ";" as a splitter + between multiple commands. + Thus, without the quotes, + <filename>devtool add</filename> does not receive the + other parts, which results in several "command not + found" errors. + </para></listitem> + <listitem><para> + In order to support adding + Node.js modules, a + <filename>nodejs</filename> recipe must be part of your + SDK in order to provide Node.js + itself. + </para></listitem> + </itemizedlist> + </note> + </para> + </section> +</section> + +<section id='sdk-working-with-recipes'> + <title>Working With Recipes</title> + + <para> + When building a recipe with <filename>devtool build</filename> the + typical build progression is as follows: + <orderedlist> + <listitem><para> + Fetch the source + </para></listitem> + <listitem><para> + Unpack the source + </para></listitem> + <listitem><para> + Configure the source + </para></listitem> + <listitem><para> + Compiling the source + </para></listitem> + <listitem><para> + Install the build output + </para></listitem> + <listitem><para> + Package the installed output + </para></listitem> + </orderedlist> + For recipes in the workspace, fetching and unpacking is disabled + as the source tree has already been prepared and is persistent. + Each of these build steps is defined as a function, usually with a + "do_" prefix. + These functions are typically shell scripts but can instead be written + in Python. + </para> + + <para> + If you look at the contents of a recipe, you will see that the + recipe does not include complete instructions for building the + software. + Instead, common functionality is encapsulated in classes inherited + with the <filename>inherit</filename> directive, leaving the recipe + to describe just the things that are specific to the software to be + built. + A <ulink url='ref-classes-base'><filename>base</filename></ulink> + class exists that is implicitly inherited by all recipes and provides + the functionality that most typical recipes need. + </para> + + <para> + The remainder of this section presents information useful when + working with recipes. + </para> + + <section id='sdk-finding-logs-and-work-files'> + <title>Finding Logs and Work Files</title> + + <para> + When you are debugging a recipe that you previously created using + <filename>devtool add</filename> or whose source you are modifying + by using the <filename>devtool modify</filename> command, after + the first run of <filename>devtool build</filename>, you will + find some symbolic links created within the source tree: + <filename>oe-logs</filename>, which points to the directory in + which log files and run scripts for each build step are created + and <filename>oe-workdir</filename>, which points to the temporary + work area for the recipe. + You can use these links to get more information on what is + happening at each build step. + </para> + + <para> + These locations under <filename>oe-workdir</filename> are + particularly useful: + <itemizedlist> + <listitem><para><filename>image/</filename>: + Contains all of the files installed at the + <ulink url='&YOCTO_DOCS_REF_URL;ref-tasks-install'><filename>do_install</filename></ulink> + stage. + Within a recipe, this directory is referred to by the + expression + <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-D'><filename>D</filename></ulink><filename>}</filename>. + </para></listitem> + <listitem><para><filename>sysroot-destdir/</filename>: + Contains a subset of files installed within + <filename>do_install</filename> that have been put into the + shared sysroot. + For more information, see the + "<link linkend='sdk-sharing-files-between-recipes'>Sharing Files Between Recipes</link>" + section. + </para></listitem> + <listitem><para><filename>packages-split/</filename>: + Contains subdirectories for each package produced by the + recipe. + For more information, see the + "<link linkend='sdk-packaging'>Packaging</link>" section. + </para></listitem> + </itemizedlist> + </para> + </section> + + <section id='sdk-setting-configure-arguments'> + <title>Setting Configure Arguments</title> + + <para> + If the software your recipe is building uses GNU autoconf, + then a fixed set of arguments is passed to it to enable + cross-compilation plus any extras specified by + <ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OECONF'><filename>EXTRA_OECONF</filename></ulink> + set within the recipe. + If you wish to pass additional options, add them to + <filename>EXTRA_OECONF</filename>. + Other supported build tools have similar variables + (e.g. + <ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OECMAKE'><filename>EXTRA_OECMAKE</filename></ulink> + for CMake, + <ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OESCONS'><filename>EXTRA_OESCONS</filename></ulink> + for Scons, and so forth). + If you need to pass anything on the <filename>make</filename> + command line, you can use <filename>EXTRA_OEMAKE</filename> to do + so. + </para> + + <para> + You can use the <filename>devtool configure-help</filename> command + to help you set the arguments listed in the previous paragraph. + The command determines the exact options being passed, and shows + them to you along with any custom arguments specified through + <filename>EXTRA_OECONF</filename>. + If applicable, the command also shows you the output of the + configure script's "‐‐help" option as a reference. + </para> + </section> + + <section id='sdk-sharing-files-between-recipes'> + <title>Sharing Files Between Recipes</title> + + <para> + Recipes often need to use files provided by other recipes on + the build host. + For example, an application linking to a common library needs + access to the library itself and its associated headers. + The way this access is accomplished within the extensible SDK is + through the sysroot. + One sysroot exists per "machine" for which the SDK is being built. + In practical terms, this means a sysroot exists for the target + machine, and a sysroot exists for the build host. + </para> + + <para> + Recipes should never write files directly into the sysroot. + Instead, files should be installed into standard locations + during the + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink> + task within the + <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-D'><filename>D</filename></ulink><filename>}</filename> + directory. + A subset of these files automatically go into the sysroot. + The reason for this limitation is that almost all files that go + into the sysroot are cataloged in manifests in order to ensure + they can be removed later when a recipe is modified or removed. + Thus, the sysroot is able to remain free from stale files. + </para> + </section> + + <section id='sdk-packaging'> + <title>Packaging</title> + + <para> + Packaging is not always particularly relevant within the + extensible SDK. + However, if you examine how build output gets into the final image + on the target device, it is important to understand packaging + because the contents of the image are expressed in terms of + packages and not recipes. + </para> + + <para> + During the + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-package'><filename>do_package</filename></ulink> + task, files installed during the + <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-install'><filename>do_install</filename></ulink> + task are split into one main package, which is almost always named + the same as the recipe, and several other packages. + This separation is done because not all of those installed files + are always useful in every image. + For example, you probably do not need any of the documentation + installed in a production image. + Consequently, for each recipe the documentation files are separated + into a <filename>-doc</filename> package. + Recipes that package software that has optional modules or + plugins might do additional package splitting as well. + </para> + + <para> + After building a recipe you can see where files have gone by + looking in the <filename>oe-workdir/packages-split</filename> + directory, which contains a subdirectory for each package. + Apart from some advanced cases, the + <ulink url='&YOCTO_DOCS_REF_URL;#var-PACKAGES'><filename>PACKAGES</filename></ulink> + and + <ulink url='&YOCTO_DOCS_REF_URL;#var-FILES'><filename>FILES</filename></ulink> + variables controls splitting. + The <filename>PACKAGES</filename> variable lists all of the + packages to be produced, while the <filename>FILES</filename> + variable specifies which files to include in each package, + using an override to specify the package. + For example, <filename>FILES_${PN}</filename> specifies the files + to go into the main package (i.e. the main package is named the + same as the recipe and + <filename>${</filename><ulink url='&YOCTO_DOCS_REF_URL;#var-PN'><filename>PN</filename></ulink><filename>}</filename> + evaluates to the recipe name). + The order of the <filename>PACKAGES</filename> value is significant. + For each installed file, the first package whose + <filename>FILES</filename> value matches the file is the package + into which the file goes. + Defaults exist for both the <filename>PACKAGES</filename> and + <filename>FILES</filename> variables. + Consequently, you might find you do not even need to set these + variables in your recipe unless the software the recipe is + building installs files into non-standard locations. + </para> + </section> +</section> + +<section id='sdk-restoring-the-target-device-to-its-original-state'> + <title>Restoring the Target Device to its Original State</title> + + <para> + If you use the <filename>devtool deploy-target</filename> + command to write a recipe's build output to the target, and + you are working on an existing component of the system, then you + might find yourself in a situation where you need to restore the + original files that existed prior to running the + <filename>devtool deploy-target</filename> command. + Because the <filename>devtool deploy-target</filename> command + backs up any files it overwrites, you can use the + <filename>devtool undeploy-target</filename> to restore those files + and remove any other files the recipe deployed. + Consider the following example: + <literallayout class='monospaced'> + $ devtool undeploy-target lighttpd root@192.168.7.2 + </literallayout> + If you have deployed multiple applications, you can remove them + all at once thus restoring the target device back to its + original state: + <literallayout class='monospaced'> + $ devtool undeploy-target -a root@192.168.7.2 + </literallayout> + Information about files deployed to the target as well as any + backed up files are stored on the target itself. + This storage of course requires some additional space + on the target machine. + <note> + The <filename>devtool deploy-target</filename> and + <filename>devtool undeploy-target</filename> command do not + currently interact with any package management system on the + target device (e.g. RPM or OPKG). + Consequently, you should not intermingle operations + <filename>devtool deploy-target</filename> and the package + manager operations on the target device. + Doing so could result in a conflicting set of files. + </note> + </para> +</section> + +<section id='sdk-installing-additional-items-into-the-extensible-sdk'> + <title>Installing Additional Items Into the Extensible SDK</title> + + <para> + The extensible SDK typically only comes with a small number of tools + and libraries out of the box. + If you have a minimal SDK, then it starts mostly empty and is + populated on-demand. + However, sometimes you will need to explicitly install extra items + into the SDK. + If you need these extra items, you can first search for the items + using the <filename>devtool search</filename> command. + For example, suppose you need to link to libGL but you are not sure + which recipe provides it. + You can use the following command to find out: + <literallayout class='monospaced'> + $ devtool search libGL + mesa A free implementation of the OpenGL API + </literallayout> + Once you know the recipe (i.e. <filename>mesa</filename> in this + example), you can install it: + <literallayout class='monospaced'> + $ devtool sdk-install mesa + </literallayout> + By default, the <filename>devtool sdk-install</filename> assumes the + item is available in pre-built form from your SDK provider. + If the item is not available and it is acceptable to build the item + from source, you can add the "-s" option as follows: + <literallayout class='monospaced'> + $ devtool sdk-install -s mesa + </literallayout> + It is important to remember that building the item from source takes + significantly longer than installing the pre-built artifact. + Also, if no recipe exists for the item you want to add to the SDK, you + must instead add it using the <filename>devtool add</filename> command. + </para> +</section> + +<section id='sdk-updating-the-extensible-sdk'> + <title>Updating the Extensible SDK</title> + + <para> + If you are working with an extensible SDK that gets occasionally + updated (e.g. typically when that SDK has been provided to you by + another party), then you will need to manually pull down those + updates to your installed SDK. + </para> + + <para> + To update your installed SDK, run the following: + <literallayout class='monospaced'> + $ devtool sdk-update + </literallayout> + The previous command assumes your SDK provider has set the default + update URL for you. + If that URL has not been set, you need to specify it yourself as + follows: + <literallayout class='monospaced'> + $ devtool sdk-update <replaceable>path_to_update_directory</replaceable> + </literallayout> + <note> + The URL needs to point specifically to a published SDK and not an + SDK installer that you would download and install. + </note> + </para> +</section> + +<section id='sdk-creating-a-derivative-sdk-with-additional-components'> + <title>Creating a Derivative SDK With Additional Components</title> + + <para> + You might need to produce an SDK that contains your own custom + libraries for sending to a third party (e.g., if you are a vendor with + customers needing to build their own software for the target platform). + If that is the case, then you can produce a derivative SDK based on + the currently installed SDK fairly easily. + Use these steps: + <orderedlist> + <listitem><para>If necessary, install an extensible SDK that + you want to use as a base for your derivative SDK. + </para></listitem> + <listitem><para>Source the environment script for the SDK. + </para></listitem> + <listitem><para>Add the extra libraries or other components + you want by using the <filename>devtool add</filename> + command. + </para></listitem> + <listitem><para>Run the <filename>devtool build-sdk</filename> + command. + </para></listitem> + </orderedlist> + The above procedure takes the recipes added to the workspace and + constructs a new SDK installer containing those recipes and the + resulting binary artifacts. + The recipes go into their own separate layer in the constructed + derivative SDK, leaving the workspace clean and ready for users + to add their own recipes. + </para> +</section> + +</chapter> +<!-- +vim: expandtab tw=80 ts=4 +--> |
