[igt-dev] Writeback Assumptions for XRGB

[Pekka Paalanen]

On Fri, 4 Mar 2022 15:46:07 +0100
Maxime Ripard <maxime at cerno.tech> wrote:

> Indeed, while the input buffer uses 0xff for the X component, we'll get
> back 0x00 from the hardware, and thus the hashes are not identical. We
> can force the hardware to always set it to 0xff, but that doesn't seem
> right. It would make more sense to ignore the X component entirely in
> that case.

Hi,

I tried hard to send a slightly longer response, but gmail refuses to
deliver to anyone without explanation. So here's a summary of my opinion:

- KMS must ignore X channel contents on read
- IGT must ignore X channel contents when comparing results
- it would be nice if IGT filled image X channels with garbage to
  verify the first two points


Thanks,
pq
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