[TF-A] Proposal: TF-A to adopt hand-off blocks (HOBs) for information passing between boot stages

[Julius Werner]

> - "bloblist" is a general term for concept of linked list and it's not exactly U-boot implementation. The proposed solution will cause some degree of changes in all the participating projects. For backward compatibility issue, we have already though about it and proposed to have build configs which will be enabled by platform integrators.

Okay, let's gather the requirements and then decide how the existing
system needs to be expanded to meet them. Please keep me in the loop
on those discussions.

> > U-Boot has an established mechanism which is used in particular on all chrome
> > books in both x86 and Arm environments.  I have the impression that
> > U-Boot is the typical BL33 so I would import the mechanism into TFA,
> > not the other way round.

There has been no Chromebook (x86 or Arm) shipping with U-Boot since
2013 (before TF-A existed). In fact, Chromebooks are all running
coreboot today and using the bl_aux_params mechanism (it's 3 SoC
vendors, more than 3 SoCs, but the parameter code is shared at the
vendor level), and one of my concerns here is trying to limit
disruption to those existing setups. I don't have enough data to say
what the "typical" boot flow among all TF-A devices in existence is,
but at least for the millions of Chromebooks out there it is coreboot
+ TF-A, not U-Boot.