[PATCH v5 05/17] drm/display: hdmi-state-helper: Act on color format DRM property

[Maxime Ripard]

On Thu, Dec 11, 2025 at 08:42:00PM +0100, Nicolas Frattaroli wrote:
> On Tuesday, 9 December 2025 15:16:58 Central European Standard Time Maxime Ripard wrote:
> > On Fri, Nov 28, 2025 at 10:05:41PM +0100, Nicolas Frattaroli wrote:
> > > With the introduction of the "color format" DRM property, which allows
> > > userspace to request a specific color format, the HDMI state helper
> > > should implement this.
> > > 
> > > Implement it by checking whether the property is set and set to
> > > something other than auto. If so, pass the requested color format, and
> > > otherwise set RGB.
> > > 
> > > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli at collabora.com>
> > > ---
> > >  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 12 +++++++++++-
> > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > > index a561f124be99..5da956bdd68c 100644
> > > --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > > +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > > @@ -649,11 +649,21 @@ hdmi_compute_config(const struct drm_connector *connector,
> > >  	unsigned int max_bpc = clamp_t(unsigned int,
> > >  				       conn_state->max_bpc,
> > >  				       8, connector->max_bpc);
> > > +	enum hdmi_colorspace hdmi_colorspace =
> > > +		drm_color_format_to_hdmi_colorspace(conn_state->color_format);
> > >  	int ret;
> > >  
> > >  	ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
> > > -				      HDMI_COLORSPACE_RGB);
> > > +				      hdmi_colorspace);
> > >  	if (ret) {
> > > +		/* If a color format was explicitly requested, don't fall back */
> > > +		if (conn_state->color_format) {
> > > +			drm_dbg_kms(connector->dev,
> > > +				    "Explicitly set color format '%s' doesn't work.\n",
> > > +				    drm_get_color_format_name(conn_state->color_format));
> > > +			return ret;
> > > +		}
> > > +
> > 
> > I think the following would be more readable:
> > 
> > 
> > if (conn_state->color_format && conn_state->color_format != DRM_COLOR_FORMAT_AUTO) {
> >     enum hdmi_colorspace hdmi_colorspace =
> >         drm_color_format_to_hdmi_colorspace(conn_state->color_format);
> > 
> >     return hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc, hdmi_colorspace)
> > }
> > 
> > ret = ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
> >                                     HDMI_COLORSPACE_RGB);
> > 
> > ...
> 
> I think I get what you mean: if conn_state->color_format is set, return
> directly, instead of bailing out in the fallback path. I can do that.

Yes

> However, `conn_state->color_format && conn_state->color_format != DRM_COLOR_FORMAT_AUTO`
> is redundant now as of v5 since DRM_COLOR_FORMAT_AUTO is 0 (and
> I use its falsy nature in many other places, and don't intend to
> stop doing that).

Ok, that makes sense.

Maxime
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