drm/i915: hdmi: add CEC notifier to intel_hdmi

This patchs adds the cec_notifier feature to the intel_hdmi part
of the i915 DRM driver. It uses the HDMI DRM connector name to differentiate
between each HDMI ports.
The changes will allow the i915 HDMI code to notify EDID and HPD changes
to an eventual CEC adapter.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/gpu/drm/i915/intel_display.h

@@ -126,6 +126,30 @@ enum port {
 
 #define port_name(p) ((p) + 'A')
 
+/*
+ * Ports identifier referenced from other drivers.
+ * Expected to remain stable over time
+ */
+static inline const char *port_identifier(enum port port)
+{
+	switch (port) {
+	case PORT_A:
+		return "Port A";
+	case PORT_B:
+		return "Port B";
+	case PORT_C:
+		return "Port C";
+	case PORT_D:
+		return "Port D";
+	case PORT_E:
+		return "Port E";
+	case PORT_F:
+		return "Port F";
+	default:
+		return "<invalid>";
+	}
+}
+
 enum dpio_channel {
 	DPIO_CH0,
 	DPIO_CH1