doc: uefi: Update the capsule update related documentation

Update the capsule update functionality related documentation to
refect the additional definitions that need to be made per platform
for supporting the capsule update feature.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>

1 files changed, 98 insertions, 2 deletions

diff --git a/doc/develop/uefi/uefi.rst b/doc/develop/uefi/uefi.rst
index fe337c8..753a4e5 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
@@ -333,8 +333,104 @@ 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 values need to be defined in the board file for performing the
+capsule update. These values are defined in the board file by
+initialisation of a structure which provides information needed for
+capsule updates. The following structures have been defined for
+containing the image related information
+
+.. code-block:: c
+
+	struct efi_fw_image {
+		efi_guid_t image_type_id;
+		u16 *fw_name;
+		u8 image_index;
+	};
+
+	struct efi_capsule_update_info {
+		const char *dfu_string;
+		struct efi_fw_image *images;
+	};
+
+
+A string is defined which is to be used for populating the
+dfu_alt_info variable. This string is used by the function
+set_dfu_alt_info. Instead of taking the variable from the environment,
+the capsule update feature requires that the variable be set through
+the function, since that is more robust. Allowing the user to change
+the location of the firmware updates is not a very secure
+practice. Getting this information from the firmware itself is more
+secure, assuming the firmware has been verified by a previous stage
+boot loader.
+
+The firmware images structure defines the GUID values, image index
+values and the name of the images that are to be updated through
+the capsule update feature. These values are to be defined as part of
+an 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 be one greater than the dfu alt number that
+corresponds to the firmware image. So, if the dfu alt number for an
+image is 2, the value of image index in the fw_images array for that
+image should be 3. The dfu alt number can be obtained by running the
+following command::
+
+    dfu list
+
+When using the FMP for FIT images, the image index value needs to be
+set to 1.
+
 Finally, the capsule update can be initiated by rebooting the board.
 
+An example of setting the values in the struct efi_fw_image and
+struct efi_capsule_update_info is shown below
+
+.. code-block:: c
+
+	struct efi_fw_image fw_images[] = {
+		{
+			.image_type_id = DEVELOPERBOX_UBOOT_IMAGE_GUID,
+			.fw_name = u"DEVELOPERBOX-UBOOT",
+			.image_index = 1,
+		},
+		{
+			.image_type_id = DEVELOPERBOX_FIP_IMAGE_GUID,
+			.fw_name = u"DEVELOPERBOX-FIP",
+			.image_index = 2,
+		},
+		{
+			.image_type_id = DEVELOPERBOX_OPTEE_IMAGE_GUID,
+			.fw_name = u"DEVELOPERBOX-OPTEE",
+			.image_index = 3,
+		},
+	};
+
+	struct efi_capsule_update_info update_info = {
+		.dfu_string = "mtd nor1=u-boot.bin raw 200000 100000;"
+				"fip.bin raw 180000 78000;"
+				"optee.bin raw 500000 100000",
+		.images = fw_images,
+	};
+
+Platforms must declare a variable update_info of type struct
+efi_capsule_update_info as shown in the example above. The platform
+will also define a fw_images array which contains information of all
+the firmware images that are to be updated through capsule update
+mechanism. The dfu_string is the string that is to be set as
+dfu_alt_info. In the example above, the image index to be set for
+u-boot.bin binary is 0x1, for fip.bin is 0x2 and for optee.bin is 0x3.
+
+As an example, for generating the capsule for the optee.bin image, the
+following command can be issued
+
+.. code-block:: bash
+
+    $ ./tools/mkeficapsule \
+      --index 0x3 --instance 0 \
+      --guid c1b629f1-ce0e-4894-82bf-f0a38387e630 \
+      optee.bin optee.capsule
+
+
 Enabling Capsule Authentication
 *******************************