sdk-manual: Added sections in Appendix B.
(From yocto-docs rev: 955f08c8d49fabd6022570e4d0a7442f06f6049b) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
Richard Purdie
parent
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commit
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@ -383,6 +383,613 @@
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</para>
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</section>
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<section id='sdk-a-closer-look-at-devtool-add'>
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<title>A Closer Look at <filename>devtool add</filename></title>
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<para>
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The <filename>devtool add</filename> command automatically creates a
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recipe based on the source tree with which you provide it.
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Currently, the command has support for the following:
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<itemizedlist>
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<listitem><para>
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Autotools (<filename>autoconf</filename> and
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<filename>automake</filename>)
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</para></listitem>
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<listitem><para>
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<filename>CMake</filename>
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</para></listitem>
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<listitem><para>
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<filename>Scons</filename>
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</para></listitem>
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<listitem><para>
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<filename>qmake</filename>
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</para></listitem>
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<listitem><para>
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Plain <filename>Makefile</filename>
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</para></listitem>
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<listitem><para>
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Out-of-tree kernel module
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</para></listitem>
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<listitem><para>
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Binary package (i.e. "-b" option)
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</para></listitem>
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<listitem><para>
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<filename>Node.js</filename> module through
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<filename>npm</filename>
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</para></listitem>
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<listitem><para>
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Python modules that use <filename>setuptools</filename>
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or <filename>distutils</filename>
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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Apart from binary packages, the determination of how a source tree
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should be treated is automatic based on the files present within
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that source tree.
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For example, if a <filename>CMakeLists.txt</filename> file is found,
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then the source tree is assumed to be using
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<filename>CMake</filename> and is treated accordingly.
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<note>
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In most cases, you need to edit the automatically generated
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recipe in order to make it build properly.
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Typically, you would go through several edit and build cycles
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until you can build the recipe.
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Once the recipe can be built, you could use possible further
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iterations to test the recipe on the target device.
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</note>
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</para>
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<para>
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The remainder of this section covers specifics regarding how parts
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of the recipe are generated.
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</para>
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<section id='sdk-name-and-version'>
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<title>Name and Version</title>
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<para>
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If you do not specify a name and version on the command
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line, <filename>devtool add</filename> attempts to determine
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the name and version of the software being built from
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various metadata within the source tree.
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Furthermore, the command sets the name of the created recipe
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file accordingly.
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If the name or version cannot be determined, the
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<filename>devtool add</filename> command prints an error and
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you must re-run the command with both the name and version
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or just the name or version specified.
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</para>
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<para>
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Sometimes the name or version determined from the source tree
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might be incorrect.
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For such a case, you must run the following commands:
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<literallayout class='monospaced'>
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$ devtool reset -n <replaceable>recipename</replaceable>
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</literallayout>
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After running the <filename>devtool reset</filename> command,
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you need to run <filename>devtool add</filename> again and
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provide the name or the version.
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</para>
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</section>
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<section id='sdk-dependency-detection-and-mapping'>
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<title>Dependency Detection and Mapping</title>
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<para>
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The <filename>devtool add</filename> command attempts to
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detect build-time dependencies and map them to other recipes
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in the system.
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During this mapping, the command fills in the names of those
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recipes in the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-DEPENDS'><filename>DEPENDS</filename></ulink>
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value within the recipe.
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If a dependency cannot be mapped, then a comment is placed in
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the recipe indicating such.
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The inability to map a dependency might be caused because the
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naming is not recognized or because the dependency simply is
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not available.
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For cases where the dependency is not available, you must use
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the <filename>devtool add</filename> command to add an
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additional recipe to satisfy the dependency and then come
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back to the first recipe and add its name to
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<filename>DEPENDS</filename>.
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</para>
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<para>
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If you need to add runtime dependencies, you can do so by
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adding the following to your recipe:
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<literallayout class='monospaced'>
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RDEPENDS_${PN} += "dependency1 dependency2 ..."
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</literallayout>
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<note>
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The <filename>devtool add</filename> command often cannot
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distinguish between mandatory and optional dependencies.
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Consequently, some of the detected dependencies might
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in fact be optional.
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When in doubt, consult the documentation or the configure
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script for the software the recipe is building for further
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details.
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In some cases, you might find you can substitute the
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dependency for an option to disable the associated
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functionality passed to the configure script.
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</note>
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</para>
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</section>
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<section id='sdk-license-detection'>
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<title>License Detection</title>
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<para>
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The <filename>devtool add</filename> command attempts to
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determine if the software you are adding is able to be
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distributed under a common open-source license and sets the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-LICENSE'><filename>LICENSE</filename></ulink>
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value accordingly.
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You should double-check this value against the documentation
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or source files for the software you are building and update
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that <filename>LICENSE</filename> value if necessary.
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</para>
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<para>
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The <filename>devtool add</filename> command also sets the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-LIC_FILES_CHKSUM'><filename>LIC_FILES_CHKSUM</filename></ulink>
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value to point to all files that appear to be license-related.
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However, license statements often appear in comments at the top
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of source files or within documentation.
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Consequently, you might need to amend the
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<filename>LIC_FILES_CHKSUM</filename> variable to point to one
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or more of those comments if present.
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Setting <filename>LIC_FILES_CHKSUM</filename> is particularly
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important for third-party software.
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The command attempts to ensure correct licensing should you
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upgrade the recipe to a newer upstream version in future.
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Any change in licensing is detected and you receive an error
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prompting you to check the license text again.
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</para>
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<para>
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If the <filename>devtool add</filename> command cannot
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determine licensing information, the
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<filename>LICENSE</filename> value is set to "CLOSED" and the
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<filename>LIC_FILES_CHKSUM</filename> vaule remains unset.
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This behavior allows you to continue with development but is
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unlikely to be correct in all cases.
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Consequently, you should check the documentation or source
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files for the software you are building to determine the actual
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license.
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</para>
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</section>
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<section id='sdk-adding-makefile-only-software'>
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<title>Adding Makefile-Only Software</title>
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<para>
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The use of <filename>make</filename> by itself is very common
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in both proprietary and open source software.
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Unfortunately, Makefiles are often not written with
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cross-compilation in mind.
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Thus, <filename>devtool add</filename> often cannot do very
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much to ensure that these Makefiles build correctly.
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It is very common, for example, to explicitly call
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<filename>gcc</filename> instead of using the
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<filename>CC</filename> variable.
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Usually, in a cross-compilation environment,
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<filename>gcc</filename> is the compiler for the build host
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and the cross-compiler is named something similar to
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<filename>arm-poky-linux-gnueabi-gcc</filename> and might
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require some arguments (e.g. to point to the associated sysroot
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for the target machine).
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</para>
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<para>
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When writing a recipe for Makefile-only software, keep the
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following in mind:
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<itemizedlist>
|
||||
<listitem><para>
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||||
You probably need to patch the Makefile to use
|
||||
variables instead of hardcoding tools within the
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toolchain such as <filename>gcc</filename> and
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<filename>g++</filename>.
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</para></listitem>
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<listitem><para>
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The environment in which <filename>make</filename> runs
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is set up with various standard variables for
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compilation (e.g. <filename>CC</filename>,
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<filename>CXX</filename>, and so forth) in a similar
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manner to the environment set up by the SDK's
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environment setup script.
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One easy way to see these variables is to run the
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<filename>devtool build</filename> command on the
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recipe and then look in
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<filename>oe-logs/run.do_compile</filename>.
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Towards the top of this file you will see a list of
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environment variables that are being set.
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You can take advantage of these variables within the
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Makefile.
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</para></listitem>
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<listitem><para>
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If the Makefile sets a default for a variable, that
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default overrides the value set in the environment,
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which is usually not desirable.
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In this situation, you can either patch the Makefile
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so it sets the default using the "?=" operator, or
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you can alternatively force the value on the
|
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<filename>make</filename> command line.
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To force the value on the command line, add the
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variable setting to
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<ulink url='&YOCTO_DOCS_REF_URL;#var-EXTRA_OEMAKE'><filename>EXTRA_OEMAKE</filename></ulink>
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within the recipe as follows:
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<literallayout class='monospaced'>
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EXTRA_OEMAKE += "'CC=${CC}' 'CXX=${CXX}'"
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</literallayout>
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In the above example, single quotes are used around the
|
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variable settings as the values are likely to contain
|
||||
spaces because required default options are passed to
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the compiler.
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||||
</para></listitem>
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<listitem><para>
|
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Hardcoding paths inside Makefiles is often problematic
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in a cross-compilation environment.
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This is particularly true because those hardcoded paths
|
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often point to locations on the build host and thus
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will either be read-only or will introduce
|
||||
contamination into the cross-compilation by virtue of
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being specific to the build host rather than the target.
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Patching the Makefile to use prefix variables or other
|
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path variables is usually the way to handle this.
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</para></listitem>
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<listitem><para>
|
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Sometimes a Makefile runs target-specific commands such
|
||||
as <filename>ldconfig</filename>.
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For such cases, you might be able to simply apply
|
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patches that remove these commands from the Makefile.
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</para></listitem>
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||||
</itemizedlist>
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||||
</para>
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||||
</section>
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<section id='sdk-adding-native-tools'>
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<title>Adding Native Tools</title>
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<para>
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Often, you need to build additional tools that run on the
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build host system as opposed to the target.
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You should indicate this using one of the following methods
|
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when you run <filename>devtool add</filename>:
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<itemizedlist>
|
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<listitem><para>
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Specify the name of the recipe such that it ends
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with "-native".
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Specifying the name like this produces a recipe that
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only builds for the build host.
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</para></listitem>
|
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<listitem><para>
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Specify the "‐‐also-native" option with the
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<filename>devtool add</filename> command.
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Specifying this option creates a recipe file that still
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||||
builds for the target but also creates a variant with
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||||
a "-native" suffix that builds for the build host.
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||||
</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
|
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typically accomplish this by building the native and target
|
||||
parts separately rather than within the same compilation
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||||
process.
|
||||
Realize though that with the "‐‐also-native" option, you
|
||||
can add the tool using just one recipe file.
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||||
</note>
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||||
</para>
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||||
</section>
|
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|
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<section id='sdk-adding-node-js-modules'>
|
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<title>Adding <filename>Node.js</filename> Modules</title>
|
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|
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<para>
|
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You can use the <filename>devtool add</filename> command in the
|
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following form to add <filename>Node.js</filename> modules:
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<literallayout class='monospaced'>
|
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$ devtool add "npm://registry.npmjs.org;name=forever;version=0.15.1"
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||||
</literallayout>
|
||||
The name and version parameters are mandatory.
|
||||
Lockdown and shrinkwrap files are generated and pointed to by
|
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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, <filename>devtool add</filename> does not receive
|
||||
the other parts resulting in several "command not found"
|
||||
errors.
|
||||
</para></listitem>
|
||||
<listitem><para>
|
||||
In order to support adding
|
||||
<filename>Node.js</filename> modules, a
|
||||
<filename>nodejs</filename> recipe must be part of your
|
||||
SDK in order to provide <filename>Node.js</filename>
|
||||
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 workflow 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. (more on "Packaging" below)
|
||||
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 <filename>Scons</filename>, 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 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 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 ... 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 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>
|
||||
|
||||
</appendix>
|
||||
<!--
|
||||
vim: expandtab tw=80 ts=4
|
||||
|
|
|
|||
Loading…
Reference in New Issue