Documentation: dev-manual, bsp-guide, poky-ref-manual - bblayer.conf updates

Fixes [YOCTO #3176]

Several places throughout the YP manual set examples are given
for the bblayer.conf file.  For release 1.3, a bug existed that
surfaced when a user removed either the meta or meta-yocto
layer from this configuration file.  The bug has been fixed and
the ripple effect through the YP documentation set affected
several manuals.

Fixes include updating the code samples that show bblayer.conf
so that they now include the BBLAYERS_NON_REMOVABLE variable,
a new glossary entry for the variable, and an explanation of
both BBLAYER and BBLAYER_NON_REMOVABLE in the section that
talks about the bblayer.conf file.

(From yocto-docs rev: 904b9ec1cd6d823af0e92f6891fc7e434cf2e358)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

3 files changed, 48 insertions, 2 deletions

diff --git a/documentation/poky-ref-manual/ref-structure.xml b/documentation/poky-ref-manual/ref-structure.xml
index c2644df374..166907ceef 100644
--- a/documentation/poky-ref-manual/ref-structure.xml
+++ b/documentation/poky-ref-manual/ref-structure.xml
@@ -247,11 +247,20 @@
         <title><filename>build/conf/bblayers.conf</filename></title>
 
         <para>
-            This file defines layers, which is a directory tree, traversed (or walked) by BitBake. 
+            This file defines layers, which are directory trees, traversed (or walked) by BitBake.
             If <filename>bblayers.conf</filename> 
             is not present, it is created from <filename>bblayers.conf.sample</filename> when 
             you <filename>source</filename> the environment setup script.
         </para>
+
+        <para>
+            The <filename>bblayers.conf</filename> file uses the
+            <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link> variable to
+            list the layers BitBake tries to find.
+            The file uses the
+            <link linkend='var-BBLAYERS_NON_REMOVABLE'><filename>BBLAYERS_NON_REMOVABLE</filename></link>
+            variable to list layers that must not be removed.
+        </para>
     </section>
 
     <section id='structure-build-conf-sanity_info'>
diff --git a/documentation/poky-ref-manual/ref-variables.xml b/documentation/poky-ref-manual/ref-variables.xml
index 9ced42499e..0de6bfcf5c 100644
--- a/documentation/poky-ref-manual/ref-variables.xml
+++ b/documentation/poky-ref-manual/ref-variables.xml
@@ -422,6 +422,11 @@
        /home/scottrif/poky/meta-yocto-bsp \
        /home/scottrif/poky/meta-mykernel \
        "
+
+     BBLAYERS_NON_REMOVABLE ?= " \
+       /home/scottrif/poky/meta \
+       /home/scottrif/poky/meta-yocto \
+       "
                     </literallayout>
                     This example enables four layers, one of which is a custom, user-defined layer 
                     named <filename>meta-mykernel</filename>.
@@ -429,6 +434,34 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-BBLAYERS_NON_REMOVABLE'><glossterm>BBLAYERS_NON_REMOVABLE</glossterm>
+            <glossdef>
+Core layer for images cannot be removed
+                <para>Lists core layers that cannot be removed from the
+                    <filename>bblayers.conf</filename> file.
+                    In order for BitBake to build your image, your
+                    <filename>bblayers.conf</filename> file must include the
+                    <filename>meta</filename> and <filename>meta-yocto</filename>
+                    core layers.
+                    Here is an example that shows these two layers listed in
+                    the <filename>BBLAYERS_NON_REMOVABLE</filename> statement:
+                    <literallayout class='monospaced'>
+     BBLAYERS = " \
+       /home/scottrif/poky/meta \
+       /home/scottrif/poky/meta-yocto \
+       /home/scottrif/poky/meta-yocto-bsp \
+       /home/scottrif/poky/meta-mykernel \
+       "
+
+     BBLAYERS_NON_REMOVABLE ?= " \
+       /home/scottrif/poky/meta \
+       /home/scottrif/poky/meta-yocto \
+       "
+                    </literallayout>
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-BP'><glossterm>BP</glossterm>
             <glossdef>
                 <para>The base recipe name and version but without any special 
diff --git a/documentation/poky-ref-manual/technical-details.xml b/documentation/poky-ref-manual/technical-details.xml
index 654d9252a9..042a96ed87 100644
--- a/documentation/poky-ref-manual/technical-details.xml
+++ b/documentation/poky-ref-manual/technical-details.xml
@@ -662,7 +662,11 @@
         /home/nitin/prj/poky.git/meta-yocto \
         /home/nitin/prj/poky.git/meta-yocto-bsp \
         /home/nitin/prj/meta-x32.git \
-     "
+        "
+     BBLAYERS_NON_REMOVABLE ?= " \
+        /home/nitin/prj/poky.git/meta \
+        /home/nitin/prj/poky.git/meta-yocto \
+        "
                     </literallayout></para></listitem>
                 <listitem><para>Enable the x32 psABI tuning file for <filename>x86_64</filename>
                     machines by editing the <filename>conf/local.conf</filename> like this: