Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/35822 )
Change subject: arch/x86: Add a choice for selecting normal/fallback cbfs prefix ......................................................................
Patch Set 3:
CB:438 (!)
I don't think the argument about needing 'Kconfig' surgery in external tree's is a good argument as you need way more than just Kconfig surgery to make it work with more than 2 prefixes. With 2 prefixes all you can do is a cosmetic renaming. And even if those external trees have that, the option for a user selectable Kconfig is still there.
Ack, compared to CB:438, the option to enter a custom prefix is kept. We could still add the rule that one can only change the bootblock behaviour with "fallback" selected. Or maybe make it depend on the update-existing-image option. All bootblock-affecting options are void in the update case.