Re: [PATCH v5] Input: synaptics - add pass-through mode for TrackPoint

[Evan Lawrence <development@laserology.net>]

Hi Dmitry,

Following up on this thread: I am pausing all work on transparent
pass-through mode, including the v6 I mentioned (the ACK-waiting latency
reduction). I'd rather not push a workaround once the real transport works.

The reason is your original question. In my previous reply I said SMBus/RMI4
was not viable on the T14 Gen 1 because it stayed in PS/2 mode. That turned
out to be a transport bug, not a device limitation: the AMD FCH needs the
legacy SMB0001/ASF Host Notify path enabled before rmi_smbus can talk to the
touchpad. With that in place, the T14 Gen 1 AMD now runs the touchpad (F12)
and the TrackPoint (F03) natively on RMI4, with no transparent mode and no
pass-through bandwidth limit. Both devices are working on a T14 Gen 1 AMD and
on a P14s Gen 2a.

That work is being carried in a machine-specific, not-yet-upstream repository
together with Spencer Michaels, who did the original T14 Gen 2a
reverse-engineering:

  https://github.com/SpencerMichaels/t14-amd-gen2-rmi

I'll keep the transparent-mode series archived and would be glad to revive it
for any machine where RMI4 genuinely cannot work -- but that no longer looks
like the general answer to your question.

Thanks for the review feedback along the way, and to Miroslav for the
original transparent-mode work this was based on.

Also, this was my first real foray into kernel work, and parts were
LLM-assisted; I've reviewed and tested everything on the hardware. Thanks for
the patience with a newcomer.

Evan