[media] V4L: Add camera exposure metering control

The V4L2_CID_EXPOSURE_METERING control allows to determine
a method used by the camera for measuring the amount of light
available for automatic exposure.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/DocBook/media/v4l/controls.xml

@@ -2864,6 +2864,35 @@ exposure time and/or aperture.</para></entry>
 	  </row>
 	  <row><entry></entry></row>
 
+	  <row id="v4l2-exposure-metering">
+	    <entry spanname="id"><constant>V4L2_CID_EXPOSURE_METERING</constant>&nbsp;</entry>
+	    <entry>enum&nbsp;v4l2_exposure_metering</entry>
+	  </row><row><entry spanname="descr">Determines how the camera measures
+the amount of light available for the frame exposure. Possible values are:</entry>
+	  </row>
+	  <row>
+	    <entrytbl spanname="descr" cols="2">
+	      <tbody valign="top">
+		<row>
+		  <entry><constant>V4L2_EXPOSURE_METERING_AVERAGE</constant>&nbsp;</entry>
+		  <entry>Use the light information coming from the entire frame
+and average giving no weighting to any particular portion of the metered area.
+		  </entry>
+		</row>
+		<row>
+		  <entry><constant>V4L2_EXPOSURE_METERING_CENTER_WEIGHTED</constant>&nbsp;</entry>
+		  <entry>Average the light information coming from the entire frame
+giving priority to the center of the metered area.</entry>
+		</row>
+		<row>
+		  <entry><constant>V4L2_EXPOSURE_METERING_SPOT</constant>&nbsp;</entry>
+		  <entry>Measure only very small area at the center of the frame.</entry>
+		</row>
+	      </tbody>
+	    </entrytbl>
+	  </row>
+	  <row><entry></entry></row>
+
 	  <row>
 	    <entry spanname="id"><constant>V4L2_CID_PAN_RELATIVE</constant>&nbsp;</entry>
 	    <entry>integer</entry>

drivers/media/video/v4l2-ctrls.c

@@ -230,6 +230,12 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		"Aperture Priority Mode",
 		NULL
 	};
+	static const char * const camera_exposure_metering[] = {
+		"Average",
+		"Center Weighted",
+		"Spot",
+		NULL
+	};
 	static const char * const colorfx[] = {
 		"None",
 		"Black & White",
@@ -434,6 +440,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		return camera_power_line_frequency;
 	case V4L2_CID_EXPOSURE_AUTO:
 		return camera_exposure_auto;
+	case V4L2_CID_EXPOSURE_METERING:
+		return camera_exposure_metering;
 	case V4L2_CID_COLORFX:
 		return colorfx;
 	case V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE:
@@ -632,6 +640,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_IMAGE_STABILIZATION:	return "Image Stabilization";
 	case V4L2_CID_ISO_SENSITIVITY:		return "ISO Sensitivity";
 	case V4L2_CID_ISO_SENSITIVITY_AUTO:	return "ISO Sensitivity, Auto";
+	case V4L2_CID_EXPOSURE_METERING:	return "Exposure, Metering Mode";
 
 	/* FM Radio Modulator control */
 	/* Keep the order of the 'case's the same as in videodev2.h! */
@@ -783,6 +792,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
 	case V4L2_CID_MPEG_VIDEO_MPEG4_PROFILE:
 	case V4L2_CID_JPEG_CHROMA_SUBSAMPLING:
 	case V4L2_CID_ISO_SENSITIVITY_AUTO:
+	case V4L2_CID_EXPOSURE_METERING:
 		*type = V4L2_CTRL_TYPE_MENU;
 		break;
 	case V4L2_CID_LINK_FREQ:

include/linux/videodev2.h

@@ -1733,6 +1733,13 @@ enum v4l2_iso_sensitivity_auto_type {
 	V4L2_ISO_SENSITIVITY_AUTO		= 1,
 };
 
+#define V4L2_CID_EXPOSURE_METERING		(V4L2_CID_CAMERA_CLASS_BASE+25)
+enum v4l2_exposure_metering {
+	V4L2_EXPOSURE_METERING_AVERAGE		= 0,
+	V4L2_EXPOSURE_METERING_CENTER_WEIGHTED	= 1,
+	V4L2_EXPOSURE_METERING_SPOT		= 2,
+};
+
 /* FM Modulator class control IDs */
 #define V4L2_CID_FM_TX_CLASS_BASE		(V4L2_CTRL_CLASS_FM_TX | 0x900)
 #define V4L2_CID_FM_TX_CLASS			(V4L2_CTRL_CLASS_FM_TX | 1)