doc: add some image package documentation

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>

1 files changed, 50 insertions, 0 deletions

diff --git a/doc/ref_manual.rst b/doc/ref_manual.rst
index bf37a8403..7729c0aed 100644
--- a/doc/ref_manual.rst
+++ b/doc/ref_manual.rst
@@ -333,6 +333,56 @@ Compile Stage
 Install Stage
 ^^^^^^^^^^^^^
 
+TBD
+
+Targetinstall Stage
+^^^^^^^^^^^^^
+
+TBD
+
+Image Packages
+^^^^^^^^^^^^^^
+
+Image packages use a different set of variables. They have the same
+``<PKG>`` and ``<PKG>_DIR`` variables as other packages, but the rest is
+different.
+
+``<PKG>_IMAGE``
+  This is the filename of the image that is created by the rule. This is
+  usually ``$(IMAGEDIR)/<image-file-name>``.
+
+``<PKG>_FILES``
+  This is a list of tar balls that are extracted to generate the content of
+  the image. PTXdist will add the necessary dependencies to these files to
+  recreate the image as needed. If a tar ball is created by another PTXdist
+  package then this package should be selected in the menu file.
+
+``<PKG>_PKGS``
+  This is another mechanism to add files to the image. It can be uses
+  instead of or in addition to ``<PKG>_FILES``. It must be set to a list of
+  ptxdist packages (the lowercase name of the packages). PTXdist will add
+  the necessary dependencies.
+
+  Note that this will not ensure that the packages are enabled or that all
+  all package dependencies are satisfied. ``$(PTX_PACKAGES_INSTALL)`` can
+  be used to specify all enabled packages. Or ``$(call ptx/collection,
+  $(PTXDIST_WORKSPACE)/configs/<collection-file-name>)`` can be uses to to
+  specify the packages enabled by this collection. In both cases ``=`` must
+  be uses instead of ``:=`` due to the makefile include order.
+
+``<PKG>_CONFIG``
+  ``genimage`` packages use this to specify the ``genimage`` configuration
+  file. PTXdist will search for the specified file name in
+  ``config/images/`` in the BSP, platform and PTXdist in the usual search
+  order.
+
+``<PKG>_NFSROOT``
+  If this is set to ``YES`` then PTXdist will create a special nfsroot
+  directory that contains only the files from the packages specified in
+  ``<PKG>_PKGS``. This is useful if the normal nfsroot directory contains
+  conflicting files from multiple images. The created nfsroot directory is
+  ``<platform-dir>/nfsroot/<image-name>``.
+
 .. _reference_macros:
 
 Rule File Macro Reference