drm: Add a helper to forge HDMI vendor infoframes

This can then be used by DRM drivers to setup their vendor infoframes.

v2: Fix hmdi typo (Simon Farnsworth)
v3: Adapt to the hdmi_vendor_infoframe rename

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index fc481fc..7b75621 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -256,6 +256,7 @@
 struct drm_connector;
 struct drm_display_mode;
 struct hdmi_avi_infoframe;
+struct hdmi_vendor_infoframe;
 
 void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid);
 int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads);
@@ -268,5 +269,8 @@
 int
 drm_hdmi_avi_infoframe_from_display_mode(struct hdmi_avi_infoframe *frame,
 					 const struct drm_display_mode *mode);
+int
+drm_hdmi_vendor_infoframe_from_display_mode(struct hdmi_vendor_infoframe *frame,
+					    const struct drm_display_mode *mode);
 
 #endif /* __DRM_EDID_H__ */