per-plane LUTs and CSCs?

[Laurentiu Palcu]

Hi all,

I was wondering whether you could give me an advise on how to proceed further
with the following issue as I'm preparing to upstream the next set of patches
for the iMX8MQ display controller(DCSS). The display controller has 3 planes,
each with 2 CSCs and one degamma LUT. The CSCs are in front and after the LUT
respectively. Then the output from those 3 pipes is blended together and then
gamma correction is applied using a linear-to-nonlinear LUT and another CSC, if
needed.

Currently, downstream, we have all those CSCs and LUTs hard-coded into a header
file. Based on the colorspace, range, gamut selected for the output and/or
plane input, we pick up the right CSCs and LUTs from that header file to
configure our pipes... I guess this solution does the job, userspace doesn't
need to care much about how to generate those tables. But, it's also not very
flexible in case there is an app smart enough to know and actually generate
their own custom tables. :/

Looking through the dri-devel archives, I've seen that there was a tentative to
implement a more or less generic per-plane LUT/CSC solution but it didn't make
it in due to lack of userspace consumers...

Adding CSC and degamma LUT properties for each plane as well as a gamma
LUT and CSC for CRTC, would help get rid of the LUT/CSC header and rely
entirely on userspace to fill in those tables. But userspace has to know
how to generate those LUTs and colorspace conversion matrices in the
first place...

So, how should I continue with this one? Any pointers?

Thanks,
Laurentiu