[media] v4l: Add new alpha component control

The V4L2_CID_ALPHA_COMPONENT control is intended for the video capture
or memory-to-memory devices that are capable of setting up the per-pixel
alpha component to some arbitrary value. It allows to set the alpha
component for all pixels to an arbitrary value.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
index c0422c6..a1be378 100644
--- a/Documentation/DocBook/media/v4l/controls.xml
+++ b/Documentation/DocBook/media/v4l/controls.xml
@@ -324,12 +324,6 @@
 		(usually a microscope).</entry>
 	  </row>
 	  <row>
-	    <entry><constant>V4L2_CID_LASTP1</constant></entry>
-	    <entry></entry>
-	    <entry>End of the predefined control IDs (currently
-<constant>V4L2_CID_ILLUMINATORS_2</constant> + 1).</entry>
-	  </row>
-	  <row>
 	    <entry><constant>V4L2_CID_MIN_BUFFERS_FOR_CAPTURE</constant></entry>
 	    <entry>integer</entry>
 	    <entry>This is a read-only control that can be read by the application
@@ -345,6 +339,25 @@
 The value is the minimum number of OUTPUT buffers that is necessary for hardware
 to work.</entry>
 	  </row>
+	  <row id="v4l2-alpha-component">
+	    <entry><constant>V4L2_CID_ALPHA_COMPONENT</constant></entry>
+	    <entry>integer</entry>
+	    <entry> Sets the alpha color component on the capture device or on
+	    the capture buffer queue of a mem-to-mem device. When a mem-to-mem
+	    device produces frame format that includes an alpha component
+	    (e.g. <link linkend="rgb-formats">packed RGB image formats</link>)
+	    and the alpha value is not defined by the mem-to-mem input data
+	    this control lets you select the alpha component value of all
+	    pixels. It is applicable to any pixel format that contains an alpha
+	    component.
+	    </entry>
+	  </row>
+	  <row>
+	    <entry><constant>V4L2_CID_LASTP1</constant></entry>
+	    <entry></entry>
+	    <entry>End of the predefined control IDs (currently
+	      <constant>V4L2_CID_ALPHA_COMPONENT</constant> + 1).</entry>
+	  </row>
 	  <row>
 	    <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry>
 	    <entry></entry>