drm/edid: Add drm_rgb_quant_range_selectable()

drm_rgb_quant_range_selectable() will report whether the monitor
claims to support for RGB quantization range selection.

The information can be found in the CEA Video capability block.

v2: s/quantzation/quantization/ in the comment

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: David Airlie <airlied@linux.ie>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 5a3770fbd770..a3a3b61059ff 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1483,9 +1483,11 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 #define VIDEO_BLOCK     0x02
 #define VENDOR_BLOCK    0x03
 #define SPEAKER_BLOCK   0x04
+#define VIDEO_CAPABILITY_BLOCK  0x07
 #define EDID_BASIC_AUDIO        (1 << 6)
 #define EDID_CEA_YCRCB444       (1 << 5)
 #define EDID_CEA_YCRCB422       (1 << 4)
+#define EDID_CEA_VCDB_QS        (1 << 6)
 
 /**
  * Search EDID for CEA extension block.
@@ -1902,6 +1904,37 @@ end:
 EXPORT_SYMBOL(drm_detect_monitor_audio);
 
 /**
+ * drm_rgb_quant_range_selectable - is RGB quantization range selectable?
+ *
+ * Check whether the monitor reports the RGB quantization range selection
+ * as supported. The AVI infoframe can then be used to inform the monitor
+ * which quantization range (full or limited) is used.
+ */
+bool drm_rgb_quant_range_selectable(struct edid *edid)
+{
+        u8 *edid_ext;
+        int i, start, end;
+
+        edid_ext = drm_find_cea_extension(edid);
+        if (!edid_ext)
+                return false;
+
+        if (cea_db_offsets(edid_ext, &start, &end))
+                return false;
+
+        for_each_cea_db(edid_ext, i, start, end) {
+                if (cea_db_tag(&edid_ext[i]) == VIDEO_CAPABILITY_BLOCK &&
+                    cea_db_payload_len(&edid_ext[i]) == 2) {
+                        DRM_DEBUG_KMS("CEA VCDB 0x%02x\n", edid_ext[i + 2]);
+                        return edid_ext[i + 2] & EDID_CEA_VCDB_QS;
+                }
+        }
+
+        return false;
+}
+EXPORT_SYMBOL(drm_rgb_quant_range_selectable);
+
+/**
  * drm_add_display_info - pull display info out if present
  * @edid: EDID data
  * @info: display info (attached to connector)