On 2023-10-20 10:57, Pekka Paalanen wrote: > On Fri, 20 Oct 2023 16:22:56 +0200 > Sebastian Wick <sebastian.wick@xxxxxxxxxx> wrote: > >> Thanks for continuing to work on this! >> >> On Thu, Oct 19, 2023 at 05:21:22PM -0400, Harry Wentland wrote: >>> v2: >>> - Update colorop visualizations to match reality (Sebastian, Alex Hung) >>> - Updated wording (Pekka) >>> - Change BYPASS wording to make it non-mandatory (Sebastian) >>> - Drop cover-letter-like paragraph from COLOR_PIPELINE Plane Property >>> section (Pekka) >>> - Use PQ EOTF instead of its inverse in Pipeline Programming example (Melissa) >>> - Add "Driver Implementer's Guide" section (Pekka) >>> - Add "Driver Forward/Backward Compatibility" section (Sebastian, Pekka) >>> > > ... > >>> +Driver Forward/Backward Compatibility >>> +===================================== >>> + >>> +As this is uAPI drivers can't regress color pipelines that have been >>> +introduced for a given HW generation. New HW generations are free to >>> +abandon color pipelines advertised for previous generations. >>> +Nevertheless, it can be beneficial to carry support for existing color >>> +pipelines forward as those will likely already have support in DRM >>> +clients. >>> + >>> +Introducing new colorops to a pipeline is fine, as long as they can be >>> +disabled or are purely informational. DRM clients implementing support >>> +for the pipeline can always skip unknown properties as long as they can >>> +be confident that doing so will not cause unexpected results. >>> + >>> +If a new colorop doesn't fall into one of the above categories >>> +(bypassable or informational) the modified pipeline would be unusable >>> +for user space. In this case a new pipeline should be defined. >> >> How can user space detect an informational element? Should we just add a >> BYPASS property to informational elements, make it read only and set to >> true maybe? Or something more descriptive? > > Read-only BYPASS set to true would be fine by me, I guess. > Don't you mean set to false? An informational element will always do something, so it can't be bypassed. > I think we also need a definition of "informational". > > Counter-example 1: a colorop that represents a non-configurable Not sure what's "counter" for these examples? > YUV<->RGB conversion. Maybe it determines its operation from FB pixel > format. It cannot be set to bypass, it cannot be configured, and it > will alter color values. > > Counter-example 2: image size scaling colorop. It might not be > configurable, it is controlled by the plane CRTC_* and SRC_* > properties. You still need to understand what it does, so you can > arrange the scaling to work correctly. (Do not want to scale an image > with PQ-encoded values as Josh demonstrated in XDC.) > IMO the position of the scaling operation is the thing that's important here as the color pipeline won't define scaling properties. > Counter-example 3: image sampling colorop. Averages FB originated color > values to produce a color sample. Again do not want to do this with > PQ-encoded values. > Wouldn't this only happen during a scaling op? Harry > > Thanks, > pq
