dev-manual: Updates to using IMAGE_FEATURES and EXTRA_IMAGE_FEATURES

The section "Customizing Images Using Custom IMAGE_FEATURES
and EXTRA_IMAGE_FEATURES" needed a bit more clarification on
the image features.  The text pretty much passed off image
features as all mapping into package groups, which is not true.
Some, like "debug-tweaks for example, are more like general
configurations.  I updated the section accordingly.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
(From yocto-docs rev: 7dd55ff0bd6f7923e22695ed7323df5cfe17d1d4)

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

1 files changed, 11 insertions, 2 deletions

diff --git a/documentation/dev-manual/dev-manual-common-tasks.xml b/documentation/dev-manual/dev-manual-common-tasks.xml
index 17d725b3b8..1458b18bfd 100644
--- a/documentation/dev-manual/dev-manual-common-tasks.xml
+++ b/documentation/dev-manual/dev-manual-common-tasks.xml
@@ -996,11 +996,20 @@
             <para>
                 To understand how these features work, the best reference is
                 <filename>meta/classes/core-image.bbclass</filename>.
+                This class lists out the available
+                <ulink url='&YOCTO_DOCS_REF_URL;#var-IMAGE_FEATURES'><filename>IMAGE_FEATURES</filename></ulink>
+                of which most map to package groups while some, such as
+                <filename>debug-tweaks</filename> and
+                <filename>read-only-rootfs</filename>, resolve as general
+                configuration settings.
+            </para>
+
+            <para>
                 In summary, the file looks at the contents of the
                 <filename>IMAGE_FEATURES</filename> variable and then maps
-                those contents into a set of package groups.
+                or configures the feature accordingly.
                 Based on this information, the build system automatically
-                adds the appropriate packages to the
+                adds the appropriate packages or configurations to the
                 <ulink url='&YOCTO_DOCS_REF_URL;#var-IMAGE_INSTALL'><filename>IMAGE_INSTALL</filename></ulink>
                 variable.
                 Effectively, you are enabling extra features by extending the