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documentation/poky-ref-manual/ref-classes.xml: New externalsrc class 

Added a new class description for externalsrc.bbclass.  This
addition was driven by feedback from two community members
inside Intel whose feedback was picked up by Darren Hart.

Reported-by: Inaky Perez-Gonzales <inaky.perez-gonzales@intel.com>
Reported-by: Mohamed Abbas <mohamed.abbas@intel.com>
(From yocto-docs rev: 1217d26993f9e5f3e6914e366b1fed34debbd242)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark 2012-02-28 12:19:43 -06:00 committed by Richard Purdie
parent ad5de9715a
commit 36e3daf7f9
1 changed files with 60 additions and 0 deletions
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@ -519,6 +519,66 @@
</para>
</section>
<section id='ref-classes-externalsrc'>
<title>Using External Source - <filename>externalsrc.bbclass</filename></title>
<para>
You can use this class to build software from source code that is external to the
Yocto Project build system.
In other words, your source code resides in an external tree outside of the Yocto Project.
Building software from an external source tree means that the normal fetch, unpack, and
patch process is not used.
</para>
<para>
To use the class, you need to define the
<link linkend='var-S'><filename>S</filename></link> variable to point to the directory that contains the source files.
You also need to have your recipe inherit the <filename>externalsrc.bbclass</filename> class.
</para>
<para>
This class expects the source code to support recipe builds that use the
<link linkend='var-B'><filename>B</filename></link> variable to point to the directory in
which the Yocto Project build system places the generated objects built from the recipes.
By default, the <filename>B</filename> directory is set to the following, which is separate from the
source directory (<filename>S</filename>):
<literallayout class='monospaced'>
${WORKDIR}/${BPN}-{PV}/
</literallayout>
See the glossary entries for the
<link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>,
<link linkend='var-BPN'><filename>BPN</filename></link>,
<link linkend='var-PV'><filename>PV</filename></link>,
<link linkend='var-S'><filename>S</filename></link>, and
<link linkend='var-B'><filename>B</filename></link> for more information.
</para>
<para>
You can build object files in the external tree by setting the
<filename>B</filename> variable equal to <filename>"${S}"</filename>.
However, this practice does not work well if you use the source for more than one variant
(i.e., "natives" such as <filename>quilt-native</filename>,
or "crosses" such as <filename>gcc-cross</filename>).
So, be sure there are no "native", "cross", or "multilib" variants of the recipe.
</para>
<para>
If you do want to build different variants of a recipe, you can use the
<link linkend='var-BBCLASSEXTEND'><filename>BBCLASSEXTEND</filename></link> variable.
When you do, the <link linkend='var-B'><filename>B</filename></link> variable must support the
recipe's ability to build variants in different working directories.
Alternatively, you can make sure that separate recipes exist that each
use the <filename>BBCLASSEXTEND</filename> variable to build each variant.
The separate recipes can inherit a single target recipe.
</para>
<para>
For information on how to use this class, see the
"<ulink url='http://www.yoctoproject.org/docs/latest/dev-manual/dev-manual.html#building-software-from-an-external-source'>Building
Software from an External Source</ulink>" section in the Yocto Project Development Manual.
</para>
</section>
<section id='ref-classes-others'>
<title>Other Classes</title>