[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>

Documentation/DocBook/media/v4l/compat.xml

@@ -2379,6 +2379,17 @@ that used it. It was originally scheduled for removal in 2.6.35.
       </orderedlist>
     </section>
 
+    <section>
+      <title>V4L2 in Linux 3.3</title>
+      <orderedlist>
+        <listitem>
+	  <para>Added <constant>V4L2_CID_ALPHA_COMPONENT</constant> control
+	    to the <link linkend="control">User controls class</link>.
+	  </para>
+        </listitem>
+      </orderedlist>
+    </section>
+
     <section id="other">
       <title>Relation of V4L2 to other Linux multimedia APIs</title>
 

Documentation/DocBook/media/v4l/controls.xml

@@ -323,12 +323,6 @@ minimum value disables backlight compensation.</entry>
 	    <entry>Switch on or off the illuminator 1 or 2 of the device
 		(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>
@@ -345,6 +339,25 @@ and used as a hint to determine the number of OUTPUT buffers to pass to REQBUFS.
 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>

Documentation/DocBook/media/v4l/pixfmt-packed-rgb.xml

@@ -428,8 +428,11 @@ colorspace <constant>V4L2_COLORSPACE_SRGB</constant>.</para>
     <para>Bit 7 is the most significant bit. The value of a = alpha
 bits is undefined when reading from the driver, ignored when writing
 to the driver, except when alpha blending has been negotiated for a
-<link linkend="overlay">Video Overlay</link> or <link
-linkend="osd">Video Output Overlay</link>.</para>
+<link linkend="overlay">Video Overlay</link> or <link linkend="osd">
+Video Output Overlay</link> or when alpha component has been configured
+for a <link linkend="capture">Video Capture</link> by means of <link
+linkend="v4l2-alpha-component"> <constant>V4L2_CID_ALPHA_COMPONENT
+</constant> </link> control.</para>
 
     <example>
       <title><constant>V4L2_PIX_FMT_BGR24</constant> 4 &times; 4 pixel

drivers/media/video/v4l2-ctrls.c

@@ -467,6 +467,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_ILLUMINATORS_2:		return "Illuminator 2";
 	case V4L2_CID_MIN_BUFFERS_FOR_CAPTURE:	return "Minimum Number of Capture Buffers";
 	case V4L2_CID_MIN_BUFFERS_FOR_OUTPUT:	return "Minimum Number of Output Buffers";
+	case V4L2_CID_ALPHA_COMPONENT:		return "Alpha Component";
 
 	/* MPEG controls */
 	/* Keep the order of the 'case's the same as in videodev2.h! */

include/linux/videodev2.h

@@ -1204,10 +1204,10 @@ enum v4l2_colorfx {
 #define V4L2_CID_MIN_BUFFERS_FOR_CAPTURE	(V4L2_CID_BASE+39)
 #define V4L2_CID_MIN_BUFFERS_FOR_OUTPUT		(V4L2_CID_BASE+40)
 
-/* last CID + 1 */
-#define V4L2_CID_LASTP1                         (V4L2_CID_BASE+41)
+#define V4L2_CID_ALPHA_COMPONENT		(V4L2_CID_BASE+41)
 
-/* Minimum number of buffer neede by the device */
+/* last CID + 1 */
+#define V4L2_CID_LASTP1                         (V4L2_CID_BASE+42)
 
 /*  MPEG-class control IDs defined by V4L2 */
 #define V4L2_CID_MPEG_BASE 			(V4L2_CTRL_CLASS_MPEG | 0x900)