[PATCH/RFC v2 8/9] media: v4l: ctrls: Add a control for companding

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Companding refers to compression and expansion of pixel data to fit in a
smaller range. The control is named V4L2_CID_COMPANDING, and only
supports compression initially.

Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
Changes since v1:

- Rename V4L2_COMPANDING_ALAW to V4L2_COMPANDING_COMPRESS
- Document V4L2_COMPANDING_LINEAR and V4L2_COMPANDING_COMPRESS
---
 .../media/v4l/ext-ctrls-image-process.rst        | 16 ++++++++++++++++
 drivers/media/v4l2-core/v4l2-ctrls-defs.c        |  9 +++++++++
 include/uapi/linux/v4l2-controls.h               |  5 +++++
 3 files changed, 30 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
index b1c2ab2854af..d529b0a8cd41 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
@@ -55,3 +55,19 @@ Image Process Control IDs
     control value divided by e.g. 0x100, meaning that to get no
     digital gain the control value needs to be 0x100. The no-gain
     configuration is also typically the default.
+
+``V4L2_CID_COMPANDING (menu)``
+    Companding refers to compression and expansion of pixel data to fit in a
+    smaller range.
+
+
+.. tabularcolumns:: |p{5.7cm}|p{11.8cm}|
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+
+    * - ``V4L2_COMPANDING_LINEAR``
+      - No companding.
+    * - ``V4L2_COMPANDING_COMPRESS``
+      - Compress the data using a device-specific curve.
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
index 1ea52011247a..841e415a88ae 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
@@ -611,6 +611,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		"Cyclic",
 		NULL,
 	};
+	static const char * const companding[] = {
+		"Linear",
+		"A-Law",
+		NULL
+	};
 
 	switch (id) {
 	case V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ:
@@ -750,6 +755,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 		return camera_orientation;
 	case V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE:
 		return intra_refresh_period_type;
+	case V4L2_CID_COMPANDING:
+		return companding;
 	default:
 		return NULL;
 	}
@@ -1164,6 +1171,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_TEST_PATTERN:		return "Test Pattern";
 	case V4L2_CID_DEINTERLACING_MODE:	return "Deinterlacing Mode";
 	case V4L2_CID_DIGITAL_GAIN:		return "Digital Gain";
+	case V4L2_CID_COMPANDING:		return "Companding";
 
 	/* DV controls */
 	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
@@ -1421,6 +1429,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
 	case V4L2_CID_CAMERA_ORIENTATION:
 	case V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE:
 	case V4L2_CID_HDR_SENSOR_MODE:
+	case V4L2_CID_COMPANDING:
 		*type = V4L2_CTRL_TYPE_MENU;
 		break;
 	case V4L2_CID_LINK_FREQ:
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 974fd254e573..ca9e25f72886 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -1225,6 +1225,11 @@ enum v4l2_jpeg_chroma_subsampling {
 #define V4L2_CID_TEST_PATTERN			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
 #define V4L2_CID_DEINTERLACING_MODE		(V4L2_CID_IMAGE_PROC_CLASS_BASE + 4)
 #define V4L2_CID_DIGITAL_GAIN			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 5)
+#define V4L2_CID_COMPANDING			(V4L2_CID_IMAGE_PROC_CLASS_BASE + 6)
+enum v4l2_companding {
+	V4L2_COMPANDING_LINEAR		= 0,
+	V4L2_COMPANDING_COMPRESS	= 1,
+};
 
 /*  DV-class control IDs defined by V4L2 */
 #define V4L2_CID_DV_CLASS_BASE			(V4L2_CTRL_CLASS_DV | 0x900)
-- 
Regards,

Laurent Pinchart





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