drm: Add HDMI infoframe helpers

Add a generic helper to fill in an HDMI AVI infoframe with data
extracted from a DRM display mode.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 0cac551..5da1b4a 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -247,6 +247,8 @@
 struct drm_encoder;
 struct drm_connector;
 struct drm_display_mode;
+struct hdmi_avi_infoframe;
+
 void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid);
 int drm_av_sync_delay(struct drm_connector *connector,
 		      struct drm_display_mode *mode);
@@ -254,4 +256,8 @@
 				     struct drm_display_mode *mode);
 int drm_load_edid_firmware(struct drm_connector *connector);
 
+int
+drm_hdmi_avi_infoframe_from_display_mode(struct hdmi_avi_infoframe *frame,
+					 const struct drm_display_mode *mode);
+
 #endif /* __DRM_EDID_H__ */