Re: [PATCH v9 02/19] drm: Add new general DRM property "color format"

[Nicolas Frattaroli]

On Sunday, 1 March 2026 17:47:48 Central European Standard Time Dmitry Baryshkov wrote:
> On Fri, Feb 27, 2026 at 08:20:07PM +0100, Nicolas Frattaroli wrote:
> > From: Andri Yngvason <andri@xxxxxxxxxxx>
> > 
> > Add a new general DRM property named "color format" which can be used by
> > userspace to request the display driver to output a particular color
> > format.
> > 
> > Possible options are:
> >     - auto (setup by default, driver internally picks the color format)
> >     - rgb
> >     - ycbcr444
> >     - ycbcr422
> >     - ycbcr420
> > 
> > Drivers should advertise from this list which formats they support.
> > Together with this list and EDID data from the sink we should be able
> > to relay a list of usable color formats to users to pick from.
> > 
> > Signed-off-by: Werner Sembach <wse@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Andri Yngvason <andri@xxxxxxxxxxx>
> > Signed-off-by: Marius Vlad <marius.vlad@xxxxxxxxxxxxx>
> > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@xxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c |   5 ++
> >  drivers/gpu/drm/drm_atomic_uapi.c   |  11 ++++
> >  drivers/gpu/drm/drm_connector.c     | 124 ++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_connector.h         | 103 ++++++++++++++++++++++++++++++
> >  4 files changed, 243 insertions(+)
> 
> It seems and feels that the common code to be used (almost?) everywhere
> would be:
> 
> if (!drm_mode_create_color_format_property(connector, supported_formats))
> 	drm_connector_attach_color_format_property(connector);
> 
> 
> Please mention somewhere the reason to split that into two functions.
> 

There isn't one I can think of, I kept it as-is since I inherited
the code like this and figured this was the expected convention based
on drm_mode_create_hdmi_colorspace_property ->
drm_connector_attach_colorspace_property.

Quite possibly, the idea is that callers can choose to probe whether
a certain set of parameters would allow the property to be created
without attaching it during said probing, but that's speculation on
my part.

Having it work like drm_connector_attach_max_bpc_property may make
more sense here, and I'll refactor it to do this in the next revision
unless anyone has any objections.

Kind regards,
Nicolas Frattaroli