drm: detect hdmi monitor by hdmi identifier (v3)

Sometime we need to communicate with HDMI monitor by sending audio or video
info frame, so we have to know monitor type. However if user utilize HDMI-DVI adapter to connect DVI monitor, hardware detection will incorrectly show the monitor is HDMI. HDMI spec tell us that any device containing IEEE registration Identifier will be treated as HDMI device.  The patch intends to detect HDMI monitor by this rule.

Signed-off-by: Ma Ling <ling.ma@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 9022b24..3c1924c 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -732,4 +732,5 @@
 				    void *data, struct drm_file *file_priv);
 extern int drm_mode_gamma_set_ioctl(struct drm_device *dev,
 				    void *data, struct drm_file *file_priv);
+extern bool drm_detect_hdmi_monitor(struct edid *edid);
 #endif /* __DRM_CRTC_H__ */