[PATCH 2/2] ACPI: FFH: Support FF-A direct request 2 calls

[Jamie Nguyen]

On Wed, Nov 04, 2026 at 09:40:08AM +0000, Sudeep Holla wrote:
> Handling this coordination is difficult, which prompted my earlier query about
> requiring v1.3 as a baseline. On ACPI platforms, this initialization conflict
> is already an inherent issue, as the UEFI or early bootloader might negotiate
> a version before the kernel FF-A driver probes. I welcome any feedback or
> proposals on how we might cleanly resolve or track this pre-negotiated state.

>From the kernel side: the transport driver and ffh.c are the same FF-A
caller from firmware's point of view. Could a small built-in helper call
FFA_VERSION once, under a mutex, and keep the effective negotiated
version? Both would use it, with the transport's existing compatibility
handling, so it wouldn't matter which runs first.

I haven't been able to think of a clean solution for the bootloader
case, though. It looks like the same hole the transport already has
today, since the helper would negotiate the way ffa_version_check() does
now.