Add NUM_DISPLAY_TYPES query and refine display list semantics

Change-Id: I740859bfa2b126edcdf06f7b2c8208770bc864f9

include/hardware/hwcomposer_defs.h

@@ -139,6 +139,12 @@ enum {
      * returns the vsync period in nanosecond
      */
     HWC_VSYNC_PERIOD                    = 1,
+
+    /*
+     * availability: HWC_DEVICE_API_VERSION_1_1
+     * returns a mask of supported display types
+     */
+    HWC_DISPLAY_TYPES_SUPPORTED         = 2,
 };
 
 /* Allowed events for hwc_methods::eventControl() */
@@ -146,6 +152,18 @@ enum {
     HWC_EVENT_VSYNC     = 0
 };
 
+/* Display types and associated mask bits. */
+enum {
+    HWC_DISPLAY_PRIMARY     = 0,
+    HWC_DISPLAY_EXTERNAL    = 1,    // HDMI, DP, etc.
+    HWC_NUM_DISPLAY_TYPES
+};
+
+enum {
+    HWC_DISPLAY_PRIMARY_BIT     = 1 << HWC_DISPLAY_PRIMARY,
+    HWC_DISPLAY_EXTERNAL_BIT    = 1 << HWC_DISPLAY_EXTERNAL,
+};
+
 /*****************************************************************************/
 
 __END_DECLS