[PATCH v7 8/8] doc: uefi: Update the capsule update related documentation

[AKASHI Takahiro]

On Thu, Apr 14, 2022 at 04:24:48PM +0530, Sughosh Ganu wrote:
> 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.

Your code seems to expect that a global variable, "update_info", exists
for each platform.
If so, please describe this requirement explicitly in a document.

-Takahiro Akashi

> 
> Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> ---
> 
> Changes since V6:
> * Add example for the struct efi_fw_image array and struct
>   efi_capsule_update_info as suggested by Takahiro
> 
>  doc/develop/uefi/uefi.rst | 98 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 96 insertions(+), 2 deletions(-)
> 
> diff --git a/doc/develop/uefi/uefi.rst b/doc/develop/uefi/uefi.rst
> index fe337c88bd..1aea04a4e8 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
> @@ -333,9 +333,102 @@ 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_images {
> +		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,
> +	};
> +
> +The platform will 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
>  *******************************
>  
> -- 
> 2.25.1
>