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 <[e-mail]>
Reviewed-by: Simon Farnsworth <[e-mail]>
Reviewed-by: Ville Syrjälä <[e-mail]>
Reviewed-by: Thierry Reding <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/drm_edid.c

···
 	return 0;
 }
 EXPORT_SYMBOL(drm_hdmi_avi_infoframe_from_display_mode);
+
+/**
+ * drm_hdmi_vendor_infoframe_from_display_mode() - fill an HDMI infoframe with
+ * data from a DRM display mode
+ * @frame: HDMI vendor infoframe
+ * @mode: DRM display mode
+ *
+ * Note that there's is a need to send HDMI vendor infoframes only when using a
+ * 4k or stereoscopic 3D mode. So when giving any other mode as input this
+ * function will return -EINVAL, error that can be safely ignored.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int
+drm_hdmi_vendor_infoframe_from_display_mode(struct hdmi_vendor_infoframe *frame,
+					    const struct drm_display_mode *mode)
+{
+	int err;
+	u8 vic;
+
+	if (!frame || !mode)
+		return -EINVAL;
+
+	vic = drm_match_hdmi_mode(mode);
+	if (!vic)
+		return -EINVAL;
+
+	err = hdmi_vendor_infoframe_init(frame);
+	if (err < 0)
+		return err;
+
+	frame->vic = vic;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_hdmi_vendor_infoframe_from_display_mode);

include/drm/drm_edid.h

···
 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);
···
 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__ */