On Fri, 2 Jan 2026 13:40:21 -0500
Harry Wentland [off-list ref] wrote:

On 2026-01-01 07:37, Shengyu Qu wrote:

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在 2025/12/30 02:53, Shengyu Qu 写道:  

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在 2025/12/24 3:44, NÃ colas F. R. A. Prado 写道:  

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Given the lack of support for writeback connectors on the
MediaTek KMS driver, combined with limited hardware
documentation, I haven't been able to verify the correctness of
each curve, only that they were visually sane (gamma curves made
the image on the display brighter, while inverse gamma made it
darker).  

Hmmm I don't think this is acceptable. sRGB/scRGB has two transfer
functions mentioned in original specification[1]. To keep color
accuracy, we need someone from mediatek confirm whether this is
piece- wise or pure power 2.2 transfer function, this is already
done in original amdgpu color pipeline series, sRGB means
piece-wise while also dedicated power 2.2 function exists.  

Not sure what you mean with this not being acceptable. This is about
enabling HW support for this functionality. Not every HW has
writeback for testing. At some point you'll have to trust the driver
devs if you're going to use functionality of the driver. We're not
always going to get everything perfect, but if that's really such a
worry you can always use shaders to do precisely what you want.

Hi Harry,

yes, but I understood that in this case, the hardware documentation
available is so vague that it's impossible to say what it will actually
do. There are no formulas given or referenced in the documentation, are
there, Nícolas?

The "HLG EOTF" is probably a good example of that, referring to the
reply I just sent on the patch adding "HLG" as a curve.


Thanks,
pq