[PATCH v3] media: v4l2-ctrls: add control for dpcm predictor

[Prabhakar Lad <prabhakar.lad@ti.com>]

From: Lad, Prabhakar <prabhakar.lad@ti.com>

add V4L2_CID_DPCM_PREDICTOR control of type menu, which
determines the dpcm predictor. The predictor can be either
simple or advanced.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Rob Landley <rob@landley.net>
Cc: HeungJun Kim <riverful.kim@samsung.com>
---
This patches has one checkpatch warning for line over
80 characters altough it can be avoided I have kept it
for consistency.

Changes for v3:
1: Added better explanation for DPCM, pointed by Hans.

Changes for v2:
1: Added documentaion in controls.xml pointed by Sylwester.
2: Chnaged V4L2_DPCM_PREDICTOR_ADVANCE to V4L2_DPCM_PREDICTOR_ADVANCED
   pointed by Sakari.

 Documentation/DocBook/media/v4l/controls.xml |   48 +++++++++++++++++++++++++-
 drivers/media/v4l2-core/v4l2-ctrls.c         |    9 +++++
 include/linux/videodev2.h                    |    5 +++
 3 files changed, 61 insertions(+), 1 deletions(-)

diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
index 93b9c68..f704218 100644
--- a/Documentation/DocBook/media/v4l/controls.xml
+++ b/Documentation/DocBook/media/v4l/controls.xml
@@ -4267,7 +4267,53 @@ interface and may change in the future.</para>
 	    pixels / second.
 	    </entry>
 	  </row>
-	  <row><entry></entry></row>
+	  <row>
+	    <entry spanname="id"><constant>V4L2_CID_DPCM_PREDICTOR</constant></entry>
+	    <entry>menu</entry>
+	  </row>
+	  <row id="v4l2-dpcm-predictor">
+	    <entry spanname="descr"> Differential pulse-code modulation (DPCM) is a signal
+	    encoder that uses the baseline of pulse-code modulation (PCM) but adds some
+	    functionalities based on the prediction of the samples of the signal. The input
+	    can be an analog signal or a digital signal.
+
+	    <para>If the input is a continuous-time
+	    analog signal, it needs to be sampled first so that a discrete-time signal is
+	    the input to the DPCM encoder.</para>
+
+	    <para>Simple: take the values of two
+	    consecutive samples; if they are analog samples, quantize them; calculate the
+	    difference between the first one and the next; the output is the difference, and
+	    it can be further entropy coded.</para>
+
+	    <para>Advanced: instead of taking a difference relative to a previous input sample,
+	    take the difference relative to the output of a local model of the decoder process;
+	    in this option, the difference can be quantized, which allows a good way to
+	    incorporate a controlled loss in the encoding.</para>
+
+	    <para>Applying one of these two processes, short-term redundancy (positive correlation of
+	    nearby values) of the signal is eliminated; compression ratios on the order of 2 to 4
+	    can be achieved if differences are subsequently entropy coded, because the entropy of
+	    the difference signal is much smaller than that of the original discrete signal treated
+	    as independent samples.For more information about DPCM see <ulink
+	    url="http://en.wikipedia.org/wiki/Differential_pulse-code_modulation">Wikipedia</ulink>.</para>
+	    </entry>
+	  </row>
+	  <row>
+	    <entrytbl spanname="descr" cols="2">
+	      <tbody valign="top">
+	        <row>
+	         <entry><constant>V4L2_DPCM_PREDICTOR_SIMPLE</constant></entry>
+	          <entry>Predictor type is simple</entry>
+	        </row>
+	        <row>
+	          <entry><constant>V4L2_DPCM_PREDICTOR_ADVANCED</constant></entry>
+	          <entry>Predictor type is advanced</entry>
+	        </row>
+	      </tbody>
+	    </entrytbl>
+	  </row>
+	<row><entry></entry></row>
 	</tbody>
       </tgroup>
       </table>
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index b6a2ee7..2d7bc15 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -425,6 +425,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		"Gray",
 		NULL,
 	};
+	static const char * const dpcm_predictor[] = {
+		"Simple Predictor",
+		"Advanced Predictor",
+		NULL,
+	};
 
 	switch (id) {
 	case V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ:
@@ -502,6 +507,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		return mpeg4_profile;
 	case V4L2_CID_JPEG_CHROMA_SUBSAMPLING:
 		return jpeg_chroma_subsampling;
+	case V4L2_CID_DPCM_PREDICTOR:
+		return dpcm_predictor;
 
 	default:
 		return NULL;
@@ -732,6 +739,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_IMAGE_PROC_CLASS:		return "Image Processing Controls";
 	case V4L2_CID_LINK_FREQ:		return "Link Frequency";
 	case V4L2_CID_PIXEL_RATE:		return "Pixel Rate";
+	case V4L2_CID_DPCM_PREDICTOR:		return "DPCM Predictor";
 
 	default:
 		return NULL;
@@ -832,6 +840,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
 	case V4L2_CID_ISO_SENSITIVITY_AUTO:
 	case V4L2_CID_EXPOSURE_METERING:
 	case V4L2_CID_SCENE_MODE:
+	case V4L2_CID_DPCM_PREDICTOR:
 		*type = V4L2_CTRL_TYPE_MENU;
 		break;
 	case V4L2_CID_LINK_FREQ:
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index 6d6dfa7..ca9fb78 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -2000,6 +2000,11 @@ enum v4l2_jpeg_chroma_subsampling {
 
 #define V4L2_CID_LINK_FREQ			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 1)
 #define V4L2_CID_PIXEL_RATE			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 2)
+#define V4L2_CID_DPCM_PREDICTOR			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
+enum v4l2_dpcm_predictor {
+	V4L2_DPCM_PREDICTOR_SIMPLE	= 0,
+	V4L2_DPCM_PREDICTOR_ADVANCED	= 1,
+};
 
 /*
  *	T U N I N G
-- 
1.7.0.4