Re: [PATCH v3] drm: Guard DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE

[Robert Mader]

Hi,

On 09.07.26 12:02, Maarten Lankhorst wrote:
> Hey,
>
> On 7/9/26 08:44, Borah, Chaitanya Kumar wrote:
> > On 7/7/2026 6:31 PM, Maarten Lankhorst wrote:
> > > Hey,
> > >
> > > On 7/7/26 10:03, Borah, Chaitanya Kumar wrote:
> > > > On 7/3/2026 1:02 PM, Robert Mader wrote:
> > > > > The client cap is currently advertised unconditionally, even for drivers
> > > > > that do not support plane color pipelines. If clients supporting the later,
> > > > s/later/latter
> > > >
> > > > > like Wayland compositors or tools like drm_info, enable the client cap on
> > > > > such drivers they will be left without both color pipeline and the legacy
> > > > > properties COLOR_ENCODING and COLOR_RANGE, effectively breaking YUV->RGB
> > > > > conversion support.
> > > > >
> > > > > Prevent that by only marking the cap supported if there are actually planes
> > > > > with color pipelines.
> > > > >
> > > > > Note: while the color pipeline replacement for the legacy properties is
> > > > > still under review (1), we can assume that it will work as a drop-in
> > > > > replacement.
> > > > This change will but a driver can also choose to export colorops like programmable CTM_3x4 to achieve the same.
> > > >
> > > > We should also perhaps document this somewhere that if a driver supports LEGACY properties, it is imperative to implement some version of it with the color pipeline line property.
> > > Would this be doable inside drm core? Implement the color pipeline properties, get the fixed pipeline for free?
> > Right now, the Bypass(default) pipeline is automatically created when we call drm_plane_create_color_pipeline_property(), we could come up with a similar helper that could also create a pipeline that replaces the legacy properties.
> >
> > But this can't replace the existing helper entirely because some HW (though unlikely) might not support YUV buffers.
> No need to do this for free, but a cheaper way for drivers to implement legacy
> properties by only implementing the pipeline would be nice, similar to how
> atomic also implements legacy modesetting and universal planes.

I really like this idea - should we take it to the corresponding series, 
https://lore.kernel.org/dri-devel/20260623164812.81110-1-harry.wentland@xxxxxxx/ 
so the initial implementations for AMD and VKMS directly do so?

Regards

> Kind regards,
> ~Maarten Lankhorst

--
Robert Mader
Consultant Software Developer

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