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-rw-r--r-- | bitbake/doc/user-manual/user-manual-metadata.xml | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/bitbake/doc/user-manual/user-manual-metadata.xml b/bitbake/doc/user-manual/user-manual-metadata.xml index 9bdf276..73238fd 100644 --- a/bitbake/doc/user-manual/user-manual-metadata.xml +++ b/bitbake/doc/user-manual/user-manual-metadata.xml @@ -615,6 +615,46 @@ Only variable definitions and include directives are allowed in <filename>.conf</filename> files. </para> + + <section id='layers'> + <title>Layers</title> + + <para> + Layers allow you to isolate different types of + customizations from each other. + You might find it tempting to keep everything in one layer + when working on a single project. + However, the more modular you organize your Metadata, the + easier it is to cope with future changes. + </para> + + <para> + To illustrate how layers are used to keep things modular, + consider machine customizations. + These types of customizations typically reside in a special layer, + rather than a general layer, called a Board Specific Package (BSP) Layer. + Furthermore, the machine customizations should be isolated from + recipes and Metadata that support a new GUI environment, for + example. + This situation gives you a couple of layers: one for the machine + configurations, and one for the GUI environment. + It is important to understand, however, that the BSP layer can still + make machine-specific additions to recipes within + the GUI environment layer without polluting the GUI layer itself + with those machine-specific changes. + You can accomplish this through a recipe that is a BitBake append + (<filename>.bbappend</filename>) file, which is described + later in this section. + </para> + + <para> + There are certain variable specific to layers, including: + <itemizedlist> + <listitem><para><filename>LAYERDEPENDS</filename></para></listitem> + <listitem><para><filename>LAYERVERSION</filename></para></listitem> + </itemizedlist> + </para> + </section> </section> <section id='classes'> |