[PATCH v3 9/9] doc: uefi: Update the capsule update related documentation

[Sughosh Ganu]

Update the capsule update functionality related documentation to
refect the fact that a unique image GUID is to be used per image
that forms part of the capsule file.

Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
---

Changes since V2:
* Add a description for adding image index value and definition of
  set_dfu_alt_info function for the capsule updates.

 doc/develop/uefi/uefi.rst | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/doc/develop/uefi/uefi.rst b/doc/develop/uefi/uefi.rst
index fe337c88bd..403885d0f2 100644
--- a/doc/develop/uefi/uefi.rst
+++ b/doc/develop/uefi/uefi.rst
@@ -312,8 +312,8 @@ Run the following command
 .. code-block:: console
 
     $ mkeficapsule \
-      --index 1 --instance 0 \
-      [--fit <FIT image> | --raw <raw image>] \
+      --index <index> --instance 0 \
+      --guid <image GUID> \
       <capsule_file_name>
 
 Performing the update
@@ -333,6 +333,24 @@ won't be taken over across the reboot. If this is the case, you can skip
 this feature check with the Kconfig option (CONFIG_EFI_IGNORE_OSINDICATIONS)
 set.
 
+A few things need to be defined in the board file for performing the
+capsule upadte. The first is defining the function set_dfu_alt_info in
+the board file. This function sets the environment variable
+dfu_alt_info. Instead of taking the variable from the environment, the
+capsule update feature requires that the variable be set through the
+board function, since that is more robust. Secondly, define GUID
+values and image index of the images that are to be updated through
+the capsule update feature in the board file. Both the values are to
+be defined as part of the fw_images array. These GUID values would be
+used by the Firmware Management Protocol(FMP) to populate the image
+descriptor array and also displayed as part of the ESRT table. The
+image index values defined in the array should match the dfu alt
+number that corresponds to the firmware image. The dfu alt number can
+be obtained by running the following command::
+
+    dfu list
+
+
 Finally, the capsule update can be initiated by rebooting the board.
 
 Enabling Capsule Authentication
-- 
2.25.1