rmc: Extend usages of RMC_BOARD_DATA_DIRS to specify board data

Use the variable RMC_BOARD_DATA_DIRS, to disable, append to, or
override the default board data in meta-intel with boards' data
provided by users.

Ideally, users should get the updated database in the new built
image after an incremental build.

Examples of RMC database output (db):

RMC_BOARD_DATA_DIRS  = "" (disable db generation)
RMC_BOARD_DATA_DIRS_append = " top_dir" (db of defaults & user's)
RMC_BOARD_DATA_DIRS = "top_dir" (db for user's , no defaults)
RMC_BOARD_DATA_DIRS  = " " (same as "")

Signed-off-by: Jianxun Zhang <jianxun.zhang@linux.intel.com>
Signed-off-by: California Sullivan <california.l.sullivan@intel.com>

classes/rmc-boot.bbclass

@@ -9,5 +9,9 @@ inherit ${RMC_BOOTLOADER}
 do_bootimg[depends] += "${MLPREFIX}rmc-db:do_deploy"
 
 efi_populate_append() {
-        install -m 0400 ${DEPLOY_DIR_IMAGE}/rmc.db ${DEST}/rmc.db
+	if [ -f ${DEPLOY_DIR_IMAGE}/rmc.db ]; then
+		install -m 0400 ${DEPLOY_DIR_IMAGE}/rmc.db ${DEST}/rmc.db
+	else
+		rm -f ${DEST}/rmc.db
+	fi
 }

common/recipes-bsp/rmc/rmc-db.bb

@@ -14,7 +14,7 @@ S = "${WORKDIR}"
 
 inherit rmc-db
 
-RMC_BOARD_DATA_DIRS_append := " ${THISDIR}/boards/"
+RMC_BOARD_DATA_DIRS ?= "${THISDIR}/boards/"
 RMC_DB_DIR = "${WORKDIR}/db"
 
 # Let sstate be aware of change in any added board directories
@@ -41,6 +41,7 @@ do_deploy () {
 	if [ -f ${RMC_DB_DIR}/rmc.db ]; then
 		install -m 0400 ${RMC_DB_DIR}/rmc.db ${DEPLOYDIR}
 	else
+		rm -f ${DEPLOYDIR}/rmc.db
 		echo "Warning: no RMC central database found, skip deployment."
 	fi
 }

documentation/rmc/README

@@ -82,15 +82,31 @@ following this example, so that RMC recipes can pick up them correctly in build.
           |- ...more files
 
 Note 0:
-To add your boards into RMC feature, simply put this line in your
+Developers are expected to use variable RMC_BOARD_DATA_DIRS to specify data of
-rmc-db.bbappend:
+boards packed into RMC database file generated in a build. The default value of
+the variable in meta-intel specifies a group of boards. They work as examples
+and necessary quirks for these boards to function properly. Developers can
+override, append to the default boards with data of their own boards in the
+database file, or even disable the generation of the database file.
 
-RMC_BOARD_DATA_DIRS_append := " ${THISDIR}/my_top_dir"
+For example, in your local.conf file:
 
-RMC db recipe takes all top directories specified in RMC_BOARD_DATA_DIRS to
+This line adds your boards along with the default boards into RMC database file,
-construct and deploy a central RMC database inside image. The bbclass of the
+assuming you have a directory named "rmc" which has a subdirectory for each
-bare RMC project also provide function for other components to construct their
+board:
-own RMC database file. Please refer to rmc-db.bbclass for more information.
+
+RMC_BOARD_DATA_DIRS_append = " /path_of/rmc"
+
+This line directs RMC to pack data of your boards only, without data of the
+default boards in meta-intel:
+
+RMC_BOARD_DATA_DIRS = "/path_of/rmc"
+
+And this line disables database generation:
+
+RMC_BOARD_DATA_DIRS = ""
+
+Please also refer to the "Example 1" in this document.
 
 Subdirectory is not supported in a board's directory.
 
@@ -175,15 +191,8 @@ bootloader please overwrite the RMC_BOOTLOADER variable in your local.conf
 
 Note:
 Image could be still bootable if you only have either of two lines, but RMC
-feature won't be fully functional.
+feature could not be fully functional, depending on the availability of the
-
+database file, installer and the rmc tool.
-To install only the RMC client with the systemd-boot bootloader without
-including a default RMC database file, add the following lines to your
-local.conf:
-
-EFI_PROVIDER = "systemd-boot"
-IMAGE_INSTALL_append = " rmc"
-
 
 Examples
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