[media] v4l: Add premultiplied alpha flag for pixel formats

When set, the new V4L2_PIX_FMT_FLAG_PREMUL_ALPHA flag indicates that the
pixel values are premultiplied by the alpha channel value.

Signed-off-by: Laurent Pinchart <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

Documentation/DocBook/media/v4l/pixfmt.xml

@@ -135,6 +135,12 @@ extended fields were set to zero. On return drivers must set the
 <constant>V4L2_PIX_FMT_PRIV_MAGIC</constant> and all the extended fields to
 applicable values.</para></entry>
 	</row>
+	<row>
+	  <entry>__u32</entry>
+	  <entry><structfield>flags</structfield></entry>
+	    <entry>Flags set by the application or driver, see <xref
+linkend="format-flags" />.</entry>
+	</row>
       </tbody>
     </tgroup>
   </table>
@@ -220,9 +226,15 @@ codes can be used.</entry>
           and the number of valid entries in the
           <structfield>plane_fmt</structfield> array.</entry>
         </row>
+	<row>
+	  <entry>__u8</entry>
+	  <entry><structfield>flags</structfield></entry>
+	  <entry>Flags set by the application or driver, see <xref
+linkend="format-flags" />.</entry>
+	</row>
         <row>
           <entry>__u8</entry>
-          <entry><structfield>reserved[11]</structfield></entry>
+          <entry><structfield>reserved[10]</structfield></entry>
           <entry>Reserved for future extensions. Should be zeroed by the
            application.</entry>
         </row>
@@ -1079,4 +1091,21 @@ concatenated to form the JPEG stream. </para>
 	</tbody>
       </tgroup>
     </table>
+
+    <table frame="none" pgwide="1" id="format-flags">
+      <title>Format Flags</title>
+      <tgroup cols="3">
+	&cs-def;
+	<tbody valign="top">
+	  <row>
+	    <entry><constant>V4L2_PIX_FMT_FLAG_PREMUL_ALPHA</constant></entry>
+	    <entry>0x00000001</entry>
+	    <entry>The color values are premultiplied by the alpha channel
+value. For example, if a light blue pixel with 50% transparency was described by
+RGBA values (128, 192, 255, 128), the same pixel described with premultiplied
+colors would be described by RGBA values (64, 96, 128, 128) </entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
   </section>

Documentation/DocBook/media/v4l/v4l2.xml

@@ -155,7 +155,7 @@ applications. -->
 	<revnumber>3.16</revnumber>
 	<date>2014-05-27</date>
 	<authorinitials>lp</authorinitials>
-	<revremark>Extended &v4l2-pix-format;.
+	<revremark>Extended &v4l2-pix-format;. Added format flags.
 	</revremark>
       </revision>