Recommendation for identifying partition with firmware to be loaded from SD-card

[Michal Simek]

On 5/1/23 16:26, Heinrich Schuchardt wrote:
> Linux distributions are interested in providing a single image which
> enables a high number of boards to boot. This is simple if the boot
> firmware (EDK II or U-Boot) is installed on flash.
> 
> For boards that expect to load a boot loader like U-Boot from an SD-card
> it is necessary that the firmware locations for different boards
> on the SD-card don't collide.
> 
> When loading from SD-card or eMMC the sector at which the binary
> starts has to be identified. The following has been implemented:
> 
> - start from hard coded sector number
> - load file from FAT file system
> - load from given partition number
> - load from partition with boot flag set (MBR partioning only)
> - load from partition with specific type GUID
> 
> Loading by partition type GUID seems the most appropriate to avoid
> collisions between the firmware for different boards.
> 
> Often firmware is separated into multiple parts due to firmware
> restrictions, e.g. U-Boot SPL and main U-Boot (e.g. as .itb file).
> 
> Here the same considerations apply. Using a partition type GUID to
> identify further firmware parts to be loaded is best suited to
> avoid collisions.
> 
> I would suggest to add a recommendation to the EBBR specification
> to use SoC specific partition type GUIDs to identify firmware to
> be loaded from SD-card.
> 
> Please, provide your feedback.

Isn't this very similar to effort which Andre presented at Fosdem 2019?

https://archive.fosdem.org/2019/schedule/event/one_image_to_rule_them_all/attachments/slides/3342/export/events/attachments/one_image_to_rule_them_all/slides/3342/simage.pdf

Thanks,
Michal