[RFC PATCH 4/5] drm/drm_color_mgmt: add 3D LUT to color mgmt properties

[Melissa Wen]

On 06/27, Ville Syrjälä wrote:
> On Sun, Jun 19, 2022 at 09:31:03PM -0100, Melissa Wen wrote:
> > Add 3D LUT for gammar correction using a 3D lookup table.  The position
> > in the color correction pipeline where 3D LUT is applied depends on hw
> > design, being after CTM or gamma. If just after CTM, a shaper lut must
> > be set to shape the content for a non-linear space. That details should
> > be handled by the driver according to its color capabilities.
> 
> I also cooked up a WIP 3D LUT support some time ago for Intel hw:
> https://github.com/vsyrjala/linux/commits/3dlut
> But that dried up due to having no userspace for it.
> 
> I also cooked up some basic igts for it:
> https://patchwork.freedesktop.org/series/90165/

Yes, I found your work on it, so I based part of my proposal on your
previous proposal and also the cubic-LUT by Laurent for rcar-du [1].
They helped me to find a path to expose 3D LUT caps, thanks.

> 
> <snip>
> > + * “LUT3D”:
> > + *	Blob property to set the 3D LUT mapping pixel data after the color
> > + *	transformation matrix and before gamma 1D lut correction.
> 
> On Intel hw the 3DLUT is after the gamma LUT in the pipeline, which is
> where I placed it in my branch.
> 
> There is now some discussion happening about exposing some
> kind of color pipeline description/configuration properties:
> https://gitlab.freedesktop.org/pq/color-and-hdr/-/issues/11

So, initially I thought we would just map the properties according to hw
pipeline, but in fact it isn't a good path to follow and would make a
big mess, so Sebastian's proposal for a pipeline description makes a lot
of sense to me. I'll join the discussion.

Anyway, thanks for all inputs,

Melissa

[1] https://lore.kernel.org/all/20201221015730.28333-1-laurent.pinchart+renesas@ideasonboard.com/
> 
> -- 
> Ville Syrjälä
> Intel
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