On Wednesday, September 9, 2020 12:57 PM, Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx> wrote: > 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... Apart from full color management mentioned by Pekka, are there other use-cases for these per-plane props? One thing I can think of is that some drivers annoyingly only apply the per-CRTC gamma LUT to the primary plane. I think it would make more sense to not attach a gamma prop to the CRTC and instead only attach it to the primary plane to make that clear. But I guess that would also break existing user-space? The gamma LUT is currently used by some compositors to implement "night light"/redshift-like features. > 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 it wouldn't be enough for user-space to fill these gamma LUTs with linear ramps and get colors that look fine? Would the process be more involved? Would user-space need to know about the driver and generate gamma LUTs depending on the driver? That would be a show-stopper. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
