drm: get cea video id code for a given display mode

This patch adds support for getting CEA Video ID Code for a given
display mode after matching with edid_cea_modes list. Its index in
the list added with one, gives the desired code.

This exported function will be used by hdmi drivers for composing
AVI info frame data.
Signed-off-by: Stephane Marchesin <marcheu@chromium.org>
Signed-off-by: Rahul Sharma <rahul.sharma@samsung.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_edid.c

@@ -1516,6 +1516,26 @@ u8 *drm_find_cea_extension(struct edid *edid)
 }
 EXPORT_SYMBOL(drm_find_cea_extension);
 
+/*
+ * Looks for a CEA mode matching given drm_display_mode.
+ * Returns its CEA Video ID code, or 0 if not found.
+ */
+u8 drm_match_cea_mode(struct drm_display_mode *to_match)
+{
+	struct drm_display_mode *cea_mode;
+	u8 mode;
+
+	for (mode = 0; mode < drm_num_cea_modes; mode++) {
+		cea_mode = (struct drm_display_mode *)&edid_cea_modes[mode];
+
+		if (drm_mode_equal(to_match, cea_mode))
+			return mode + 1;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(drm_match_cea_mode);
+
+
 static int
 do_cea_modes (struct drm_connector *connector, u8 *db, u8 len)
 {

include/drm/drm_crtc.h

@@ -1037,6 +1037,7 @@ extern int drm_mode_gamma_get_ioctl(struct drm_device *dev,
 extern int drm_mode_gamma_set_ioctl(struct drm_device *dev,
 				    void *data, struct drm_file *file_priv);
 extern u8 *drm_find_cea_extension(struct edid *edid);
+extern u8 drm_match_cea_mode(struct drm_display_mode *to_match);
 extern bool drm_detect_hdmi_monitor(struct edid *edid);
 extern bool drm_detect_monitor_audio(struct edid *edid);
 extern int drm_mode_page_flip_ioctl(struct drm_device *dev,