drm/edid: Introduce drm_default_rgb_quant_range()

Make the code selecting the RGB quantization range a little less magicy
by wrapping it up in a small helper.

v2: s/adjusted_mode/mode in vc4 to make it actually compile
v3: Add a comment proposed by Eric

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170111141835.25369-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/drm_edid.c

@@ -3768,6 +3768,25 @@ bool drm_rgb_quant_range_selectable(struct edid *edid)
 }
 EXPORT_SYMBOL(drm_rgb_quant_range_selectable);
 
+/**
+ * drm_default_rgb_quant_range - default RGB quantization range
+ * @mode: display mode
+ *
+ * Determine the default RGB quantization range for the mode,
+ * as specified in CEA-861.
+ *
+ * Return: The default RGB quantization range for the mode
+ */
+enum hdmi_quantization_range
+drm_default_rgb_quant_range(const struct drm_display_mode *mode)
+{
+	/* All CEA modes other than VIC 1 use limited quantization range. */
+	return drm_match_cea_mode(mode) > 1 ?
+		HDMI_QUANTIZATION_RANGE_LIMITED :
+		HDMI_QUANTIZATION_RANGE_FULL;
+}
+EXPORT_SYMBOL(drm_default_rgb_quant_range);
+
 static void drm_parse_hdmi_deep_color_info(struct drm_connector *connector,
 					   const u8 *hdmi)
 {

drivers/gpu/drm/i915/intel_dp.c

@@ -1713,7 +1713,9 @@ found:
 		 * VESA DisplayPort Ver.1.2a - 5.1.1.1 Video Colorimetry
 		 */
 		pipe_config->limited_color_range =
-			bpp != 18 && drm_match_cea_mode(adjusted_mode) > 1;
+			bpp != 18 &&
+			drm_default_rgb_quant_range(adjusted_mode) ==
+			HDMI_QUANTIZATION_RANGE_LIMITED;
 	} else {
 		pipe_config->limited_color_range =
 			intel_dp->limited_color_range;

drivers/gpu/drm/i915/intel_hdmi.c

@@ -1330,7 +1330,8 @@ bool intel_hdmi_compute_config(struct intel_encoder *encoder,
 		/* See CEA-861-E - 5.1 Default Encoding Parameters */
 		pipe_config->limited_color_range =
 			pipe_config->has_hdmi_sink &&
-			drm_match_cea_mode(adjusted_mode) > 1;
+			drm_default_rgb_quant_range(adjusted_mode) ==
+			HDMI_QUANTIZATION_RANGE_LIMITED;
 	} else {
 		pipe_config->limited_color_range =
 			intel_hdmi->limited_color_range;

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -463,7 +463,9 @@ static void vc4_hdmi_encoder_mode_set(struct drm_encoder *encoder,
 	csc_ctl = VC4_SET_FIELD(VC4_HD_CSC_CTL_ORDER_BGR,
 				VC4_HD_CSC_CTL_ORDER);
 
-	if (vc4_encoder->hdmi_monitor && drm_match_cea_mode(mode) > 1) {
+	if (vc4_encoder->hdmi_monitor &&
+	    drm_default_rgb_quant_range(mode) ==
+	    HDMI_QUANTIZATION_RANGE_LIMITED) {
 		/* CEA VICs other than #1 requre limited range RGB
 		 * output unless overridden by an AVI infoframe.
 		 * Apply a colorspace conversion to squash 0-255 down

include/drm/drm_edid.h

@@ -441,6 +441,8 @@ enum hdmi_picture_aspect drm_get_cea_aspect_ratio(const u8 video_code);
 bool drm_detect_hdmi_monitor(struct edid *edid);
 bool drm_detect_monitor_audio(struct edid *edid);
 bool drm_rgb_quant_range_selectable(struct edid *edid);
+enum hdmi_quantization_range
+drm_default_rgb_quant_range(const struct drm_display_mode *mode);
 int drm_add_modes_noedid(struct drm_connector *connector,
 			 int hdisplay, int vdisplay);
 void drm_set_preferred_mode(struct drm_connector *connector,