On Wed, 19 May 2021 11:53:37 +0300 Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: ... > TL;DR: > > I would summarise my comments so far into these: > > - Telling the kernel the color spaces and letting it come up with > whatever color transformation formula from those is not enough, > because it puts the render intent policy decision in the kernel. > > - Telling the kernel what color transformations need to be done is > good, if it is clearly defined. > > - Using an enum-based UAPI to tell the kernel what color > transformations needs to be done (e.g. which EOTF or EOTF^-1 to apply > at a step in the abstract pipeline) is very likely ok for many > Wayland compositors in most cases, but may not be sufficient for all > use cases. Of course, one is always bound by what hardware can do, so > not a big deal. > > - You may need to define mutually exclusive KMS properties (referring > to my email in another branch of this email tree). > > - I'm not sure I (we?) can meaningfully review things like "SDR boost" > property until we know ourselves how to composite different types of > content together. Maybe someone else could. > > Does this help or raise thoughts? > > The work on Weston CM&HDR right now is aiming to get it up to a point > where we can start nicely testing different compositing approaches and > methods and parameters, and I expect that will also feed back into the > Wayland CM&HDR protocol design as well. I have forgot to mention one important thing: Generic Wayland compositors will be using KMS planes opportunistically. The compositor will be switching between GL and KMS compositing on-demand, refresh by refresh. This means that both GL and KMS compositing must produce identical results, or users will be seeing "color flicks" on switch. This is a practical reason why we really want to know in full detail how the KMS pipeline processes pixels. Thanks, pq
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