[media] v4l: Define a pixel format for the R-Car VSP1 2-D histogram engine

The format is used on the R-Car VSP1 video queues that carry
2-D histogram statistics data.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/v4l/meta-formats.rst

@@ -13,3 +13,4 @@ These formats are used for the :ref:`metadata` interface only.
     :maxdepth: 1
 
     pixfmt-meta-vsp1-hgo
+    pixfmt-meta-vsp1-hgt

Documentation/media/uapi/v4l/pixfmt-meta-vsp1-hgt.rst

@@ -0,0 +1,120 @@
+.. -*- coding: utf-8; mode: rst -*-
+
+.. _v4l2-meta-fmt-vsp1-hgt:
+
+*******************************
+V4L2_META_FMT_VSP1_HGT ('VSPT')
+*******************************
+
+Renesas R-Car VSP1 2-D Histogram Data
+
+
+Description
+===========
+
+This format describes histogram data generated by the Renesas R-Car VSP1
+2-D Histogram (HGT) engine.
+
+The VSP1 HGT is a histogram computation engine that operates on HSV
+data. It operates on a possibly cropped and subsampled input image and
+computes the sum, maximum and minimum of the S component as well as a
+weighted frequency histogram based on the H and S components.
+
+The histogram is a matrix of 6 Hue and 32 Saturation buckets, 192 in
+total. Each HSV value is added to one or more buckets with a weight
+between 1 and 16 depending on the Hue areas configuration. Finding the
+corresponding buckets is done by inspecting the H and S value independently.
+
+The Saturation position **n** (0 - 31) of the bucket in the matrix is
+found by the expression:
+
+    n = S / 8
+
+The Hue position **m** (0 - 5) of the bucket in the matrix depends on
+how the HGT Hue areas are configured. There are 6 user configurable Hue
+Areas which can be configured to cover overlapping Hue values:
+
+::
+
+         Area 0       Area 1       Area 2       Area 3       Area 4       Area 5
+        ________     ________     ________     ________     ________     ________
+   \   /|      |\   /|      |\   /|      |\   /|      |\   /|      |\   /|      |\   /
+    \ / |      | \ / |      | \ / |      | \ / |      | \ / |      | \ / |      | \ /
+     X  |      |  X  |      |  X  |      |  X  |      |  X  |      |  X  |      |  X
+    / \ |      | / \ |      | / \ |      | / \ |      | / \ |      | / \ |      | / \
+   /   \|      |/   \|      |/   \|      |/   \|      |/   \|      |/   \|      |/   \
+  5U   0L      0U   1L      1U   2L      2U   3L      3U   4L      4U   5L      5U   0L
+        <0..............................Hue Value............................255>
+
+When two consecutive areas don't overlap (n+1L is equal to nU) the boundary
+value is considered as part of the lower area.
+
+Pixels with a hue value included in the centre of an area (between nL and nU
+included) are attributed to that single area and given a weight of 16. Pixels
+with a hue value included in the overlapping region between two areas (between
+n+1L and nU excluded) are attributed to both areas and given a weight for each
+of these areas proportional to their position along the diagonal lines
+(rounded down).
+
+The Hue area setup must match one of the following constrains:
+
+::
+
+    0L <= 0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U
+
+::
+
+    0U <= 1L <= 1U <= 2L <= 2U <= 3L <= 3U <= 4L <= 4U <= 5L <= 5U <= 0L
+
+**Byte Order.**
+All data is stored in memory in little endian format. Each cell in the tables
+contains one byte.
+
+.. flat-table:: VSP1 HGT Data - (776 bytes)
+    :header-rows:  2
+    :stub-columns: 0
+
+    * - Offset
+      - :cspan:`4` Memory
+    * -
+      - [31:24]
+      - [23:16]
+      - [15:8]
+      - [7:0]
+    * - 0
+      - -
+      - S max [7:0]
+      - -
+      - S min [7:0]
+    * - 4
+      - :cspan:`4` S sum [31:0]
+    * - 8
+      - :cspan:`4` Histogram bucket (m=0, n=0) [31:0]
+    * - 12
+      - :cspan:`4` Histogram bucket (m=0, n=1) [31:0]
+    * -
+      - :cspan:`4` ...
+    * - 132
+      - :cspan:`4` Histogram bucket (m=0, n=31) [31:0]
+    * - 136
+      - :cspan:`4` Histogram bucket (m=1, n=0) [31:0]
+    * -
+      - :cspan:`4` ...
+    * - 264
+      - :cspan:`4` Histogram bucket (m=2, n=0) [31:0]
+    * -
+      - :cspan:`4` ...
+    * - 392
+      - :cspan:`4` Histogram bucket (m=3, n=0) [31:0]
+    * -
+      - :cspan:`4` ...
+    * - 520
+      - :cspan:`4` Histogram bucket (m=4, n=0) [31:0]
+    * -
+      - :cspan:`4` ...
+    * - 648
+      - :cspan:`4` Histogram bucket (m=5, n=0) [31:0]
+    * -
+      - :cspan:`4` ...
+    * - 772
+      - :cspan:`4` Histogram bucket (m=5, n=31) [31:0]

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -1234,6 +1234,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
 	case V4L2_TCH_FMT_TU16:		descr = "16-bit unsigned touch data"; break;
 	case V4L2_TCH_FMT_TU08:		descr = "8-bit unsigned touch data"; break;
 	case V4L2_META_FMT_VSP1_HGO:	descr = "R-Car VSP1 1-D Histogram"; break;
+	case V4L2_META_FMT_VSP1_HGT:	descr = "R-Car VSP1 2-D Histogram"; break;
 
 	default:
 		/* Compressed formats */

include/uapi/linux/videodev2.h

@@ -677,7 +677,8 @@ struct v4l2_pix_format {
 #define V4L2_TCH_FMT_TU08	v4l2_fourcc('T', 'U', '0', '8') /* 8-bit unsigned touch data */
 
 /* Meta-data formats */
-#define V4L2_META_FMT_VSP1_HGO    v4l2_fourcc('V', 'S', 'P', 'H') /* R-Car VSP1 Histogram */
+#define V4L2_META_FMT_VSP1_HGO    v4l2_fourcc('V', 'S', 'P', 'H') /* R-Car VSP1 1-D Histogram */
+#define V4L2_META_FMT_VSP1_HGT    v4l2_fourcc('V', 'S', 'P', 'T') /* R-Car VSP1 2-D Histogram */
 
 /* priv field value to indicates that subsequent fields are valid. */
 #define V4L2_PIX_FMT_PRIV_MAGIC		0xfeedcafe