V4L/DVB: videodev2: introduce a common control for chroma gain

Introduce a new control for modifying the chroma gain.  This allows for user
intervention in abnormal signal conditions cases where the decoder's chroma
AGC cannot compensate and the value needs to be adjusted manually.

This work was sponsored by EyeMagnet Limited.
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/v4l/controls.xml

@@ -266,6 +266,12 @@ minimum value disables backlight compensation.</entry>
 	    <entry>boolean</entry>
 	    <entry>Chroma automatic gain control.</entry>
 	  </row>
+	  <row>
+	    <entry><constant>V4L2_CID_CHROMA_GAIN</constant></entry>
+	    <entry>integer</entry>
+	    <entry>Adjusts the Chroma gain control (for use when chroma AGC
+	    is disabled).</entry>
+	  </row>
 	  <row>
 	    <entry><constant>V4L2_CID_COLOR_KILLER</constant></entry>
 	    <entry>boolean</entry>

include/linux/videodev2.h

@@ -1030,8 +1030,11 @@ enum v4l2_colorfx {
 
 #define V4L2_CID_ROTATE				(V4L2_CID_BASE+34)
 #define V4L2_CID_BG_COLOR			(V4L2_CID_BASE+35)
+
+#define V4L2_CID_CHROMA_GAIN                    (V4L2_CID_BASE+36)
+
 /* last CID + 1 */
-#define V4L2_CID_LASTP1                         (V4L2_CID_BASE+36)
+#define V4L2_CID_LASTP1                         (V4L2_CID_BASE+37)
 
 /*  MPEG-class control IDs defined by V4L2 */
 #define V4L2_CID_MPEG_BASE 			(V4L2_CTRL_CLASS_MPEG | 0x900)