<section id='dependencies'>
<title>Dependencies</title>
- <section id='dependencies-overview'>
- <title>Overview</title>
+ <para>
+ To allow for efficient operation given multiple processes
+ executing in parallel, BitBake handles dependencies at
+ the task level.
+ BitBake supports a robust method to handle these dependencies.
+ </para>
- <para>
- BitBake handles dependencies at the task level since to
- allow for efficient operation with multiple
- processes executing in parallel, a robust method of
- specifying task dependencies is needed.
- </para>
- </section>
+ <para>
+ This section describes several types of dependency mechanisms.
+ </para>
<section id='dependencies-internal-to-the-bb-file'>
<title>Dependencies Internal to the <filename>.bb</filename> File</title>
<para>
- Where the dependencies are internal to a given
- <filename>.bb</filename> file, the dependencies are handled by the
- previously detailed <filename>addtask</filename> directive.
+ BitBake uses the <filename>addtask</filename> directive
+ to manage dependencies that are internal to a given recipe
+ file.
+ You can use the <filename>addtask</filename> directive to
+ indicate when a task is dependent on other tasks or when
+ other tasks depend on that recipe.
+ Here is an example:
+ <literallayout class='monospaced'>
+ addtask printdate after do_fetch before do_build
+ </literallayout>
+ In this example, the <filename>printdate</filename> task is
+ depends on the completion of the <filename>do_fetch</filename>
+ task.
+ And, the <filename>do_build</filename> depends on the completion
+ of the <filename>printdate</filename> task.
</para>
</section>
<title>Build Dependencies</title>
<para>
- <filename>DEPENDS</filename> lists build time dependencies.
- The 'deptask' flag for tasks is used to signify the task of each
- item listed in <filename>DEPENDS</filename> which must have
- completed before that task can be executed.
+ BitBake uses the
+ <link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
+ variable to manage build time dependencies.
+ The "deptask" varflag for tasks signifies the task of each
+ item listed in <filename>DEPENDS</filename> that must
+ complete before that task can be executed.
+ Here is an example:
<literallayout class='monospaced'>
do_configure[deptask] = "do_populate_staging"
</literallayout>
- In the previous example, the <filename>do_populate_staging</filename>
- task of each item in <filename>DEPENDS</filename> must have completed before
+ In this example, the <filename>do_populate_staging</filename>
+ task of each item in <filename>DEPENDS</filename> must complete before
<filename>do_configure</filename> can execute.
</para>
</section>
<section id='runtime-dependencies'>
<title>Runtime Dependencies</title>
+ <para>
+ BitBake uses the
+ <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>,
+ <link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>, and
+ <link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>
+ variables to manage runtime dependencies.
+ </para>
+
<para>
The <filename>PACKAGES</filename> variable lists runtime
- packages and each of these can have <filename>RDEPENDS</filename> and
+ packages.
+ Each of those packages can have <filename>RDEPENDS</filename> and
<filename>RRECOMMENDS</filename> runtime dependencies.
- The 'rdeptask' flag for tasks is used to signify the task of each
+ The "rdeptask" flag for tasks is used to signify the task of each
item runtime dependency which must have completed before that
task can be executed.
<literallayout class='monospaced'>
<title>Recursive Dependencies</title>
<para>
- These are specified with the 'recrdeptask' flag
- which is used to signify the task(s) of dependencies
- which must have completed before that task can be
- executed.
- It works by looking though the build
- and runtime dependencies of the current recipe as well
- as any inter-task dependencies the task has,
- then adding a dependency on the listed task.
- It will then recurse through the dependencies of those
- tasks and so on.
+ BitBake uses the "recrdeptask" flag to manage
+ recursive task dependencies.
+ BitBake looks through the build-time and runtime
+ dependencies of the current recipe, looks through
+ the task's inter-task
+ dependencies, and then adds dependencies for the
+ listed task.
+ Once BitBake has accomplished this, it recursively works through
+ the dependencies of those tasks.
+ Iterative passes continue until all dependencies are discovered
+ and added.
</para>
<para>
- It may be desirable to recurse not just through the
- dependencies of those tasks but through the
- build and runtime dependencies of dependent tasks too.
- If that is the case, the taskname itself should
- be referenced in the task list (e.g.
- <filename>do_a[recrdeptask] = "do_a do_b"</filename>).
+ You might want to not only have BitBake look for
+ dependencies of those tasks, but also have BitBake look
+ for build-time and runtime dependencies of the dependent
+ tasks as well.
+ If that is the case, you need to reference the task name
+ itself in the task list:
+ <literallayout class='monospaced'>
+ do_a[recrdeptask] = "do_a do_b"
+ </literallayout>
</para>
</section>
<title>Inter-Task Dependencies</title>
<para>
- The 'depends' flag for tasks is a more generic form which
- allows an inter-dependency on specific tasks rather than specifying
+ BitBake uses the "depends" flag in a more generic form
+ to manage inter-task dependencies.
+ This more generic form allows for inter-dependency
+ checks for specific tasks rather than checks for
the data in <filename>DEPENDS</filename>.
+ Here is an example:
<literallayout class='monospaced'>
do_patch[depends] = "quilt-native:do_populate_staging"
</literallayout>
- In the previous example, the <filename>do_populate_staging</filename>
- task of the target quilt-native must have completed before the
+ In this example, the <filename>do_populate_staging</filename>
+ task of the target <filename>quilt-native</filename>
+ must have completed before the
<filename>do_patch</filename> task can execute.
</para>
<para>
- The 'rdepends' flag works in a similar way but takes targets
+ The "rdepends" flag works in a similar way but takes targets
in the runtime namespace instead of the build-time dependency
namespace.
</para>
projects / thirdparty / openembedded / openembedded-core-contrib.git / commitdiff
