Subject: [PATCH v14 13/28] drm/i915/hdmi: Implement "color format" DRM property

From: Nicolas Frattaroli <[email-masked]>
Date: Thu, 23 Apr 2026 21:03:36 +0200

Implement the "color format" DRM property for HDMI. The values of the
property include RGB, YCbCr420, YCbCr444 and Auto. Auto will pick RGB,
with a fallback to YCbCr420.

The mask of supported formats by the source exposed by the property is
an optimistic scenario, as specific DFP-related caveats can't be
established before an EDID is present.

Should the explicitly requested color format not be supported by the
sink (or by the source in combination with the sink), then an error is
returned to userspace, so that it can make a better choice.

Signed-off-by: Nicolas Frattaroli <[email-masked]>
---
 drivers/gpu/drm/i915/display/intel_hdmi.c | 52 ++++++++++++++++++++++++++++---
 1 file changed, 48 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index ee7a7655e9b4..f11658f0f1f4 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2330,10 +2330,10 @@ static int intel_hdmi_compute_output_format(struct intel_encoder *encoder,
 	return intel_hdmi_compute_clock(encoder, crtc_state, respect_downstream_limits);
 }
 
-static int intel_hdmi_compute_formats(struct intel_encoder *encoder,
-				      struct intel_crtc_state *crtc_state,
-				      const struct drm_connector_state *conn_state,
-				      bool respect_downstream_limits)
+static int intel_hdmi_compute_formats_auto(struct intel_encoder *encoder,
+					   struct intel_crtc_state *crtc_state,
+					   const struct drm_connector_state *conn_state,
+					   bool respect_downstream_limits)
 {
 	struct intel_display *display = to_intel_display(encoder);
 	struct intel_connector *connector = to_intel_connector(conn_state->connector);
@@ -2368,6 +2368,35 @@ static int intel_hdmi_compute_formats(struct intel_encoder *encoder,
 	return ret;
 }
 
+static int intel_hdmi_compute_formats(struct intel_encoder *encoder,
+				      struct intel_crtc_state *crtc_state,
+				      const struct drm_connector_state *conn_state,
+				      bool respect_downstream_limits)
+{
+	struct intel_connector *connector = to_intel_connector(conn_state->connector);
+
+	switch (conn_state->color_format) {
+	case DRM_CONNECTOR_COLOR_FORMAT_RGB444:
+		return intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+							respect_downstream_limits,
+							INTEL_OUTPUT_FORMAT_RGB);
+	case DRM_CONNECTOR_COLOR_FORMAT_YCBCR444:
+		return intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+							respect_downstream_limits,
+							INTEL_OUTPUT_FORMAT_YCBCR444);
+	case DRM_CONNECTOR_COLOR_FORMAT_YCBCR420:
+		return intel_hdmi_compute_output_format(encoder, crtc_state, connector,
+							respect_downstream_limits,
+							INTEL_OUTPUT_FORMAT_YCBCR420);
+	case DRM_CONNECTOR_COLOR_FORMAT_AUTO:
+		return intel_hdmi_compute_formats_auto(encoder, crtc_state, conn_state,
+						       respect_downstream_limits);
+	default:
+		MISSING_CASE(conn_state->color_format);
+		return -EINVAL;
+	}
+}
+
 static bool intel_hdmi_is_cloned(const struct intel_crtc_state *crtc_state)
 {
 	return crtc_state->uapi.encoder_mask &&
@@ -2740,6 +2769,20 @@ static const struct drm_connector_helper_funcs intel_hdmi_connector_helper_funcs
 	.atomic_check = intel_hdmi_connector_atomic_check,
 };
 
+static void
+intel_hdmi_attach_color_format_property(struct intel_connector *connector)
+{
+	unsigned long fmts = BIT(DRM_OUTPUT_COLOR_FORMAT_RGB444);
+
+	if (connector->base.ycbcr_420_allowed)
+		fmts |= BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR420);
+
+	if (intel_hdmi_can_ycbcr444(connector))
+		fmts |= BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR444);
+
+	drm_connector_attach_color_format_property(&connector->base, fmts);
+}
+
 static void
 intel_hdmi_add_properties(struct intel_hdmi *intel_hdmi, struct drm_connector *_connector)
 {
@@ -2752,6 +2795,7 @@ intel_hdmi_add_properties(struct intel_hdmi *intel_hdmi, struct drm_connector *_
 
 	intel_attach_hdmi_colorspace_property(&connector->base);
 	drm_connector_attach_content_type_property(&connector->base);
+	intel_hdmi_attach_color_format_property(connector);
 
 	if (DISPLAY_VER(display) >= 10)
 		drm_connector_attach_hdr_output_metadata_property(&connector->base);

-- 
2.53.0