user-manual-meta: Added the layers content from the YP manual.

Copied the Layers content from the Common Tasks section of the
YP Dev Manual.

Signed-off-by: Bill Traynor <wmat@alphatroop.com>

1 files changed, 27 insertions, 2 deletions

diff --git a/doc/user-manual/user-manual-metadata.xml b/doc/user-manual/user-manual-metadata.xml
index d395a6b1d..6f3139afa 100644
--- a/doc/user-manual/user-manual-metadata.xml
+++ b/doc/user-manual/user-manual-metadata.xml
@@ -736,7 +736,7 @@ need to import them.</para>
 		</para>
 		<para>Only variable definitions and include directives are
 			allowed in .conf files.  The following variables include:
-			[add more here]
+			
 			<itemizedlist>
 			<listitem>BITBAKE_UI</listitem>
 			<listitem>BBDEBUG</listitem>
@@ -758,8 +758,33 @@ need to import them.</para>
 		</para>
 		<section>
 		<title>Layers</title>
-		<para>[add definition and description of layers here]</para>
+		<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>
+		<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>LAYERDEPENDS</listitem>
 		<listitem>LAYERVERSION</listitem>