linux-kernel - [PATCH 1/2] media: uapi: Add V4L2_CID

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Message-Id: <20230609-v4l2-vtotal-v1-1-4b7dee7e073e@skidata.com>
Date:   Fri, 09 Jun 2023 15:15:55 +0200
From:   Benjamin Bara <bbara93@...il.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>
Cc:     laurent.pinchart@...asonboard.com, jacopo.mondi@...asonboard.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Bara <benjamin.bara@...data.com>
Subject: [PATCH 1/2] media: uapi: Add V4L2_CID_VTOTAL control

From: Benjamin Bara <benjamin.bara@...data.com>

Currently, V4L2_CID_VBLANK can be used to control the frame duration of
a stream. However, camera sensors usually have a register for the
vertical total size (image data + blanking), e.g. VMAX on the imx290.
The dependency between format height and vertical blanking results to a
change of the vertical blanking value and limits whenever the format of
the frame is changed and therefore makes it harder for user space to do
calculations, e.g. the frame duration.

V4L2_CID_VTOTAL does not depend on the format and therefore simplifies
calculations. Additionally, it represents the hardware "better" and
therefore also simplifies calculations on the driver side.

Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
---
 Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst | 6 ++++++
 drivers/media/v4l2-core/v4l2-ctrls-defs.c                        | 1 +
 include/uapi/linux/v4l2-controls.h                               | 1 +
 3 files changed, 8 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
index 71f23f131f97..e72d1363ad85 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
@@ -59,6 +59,12 @@ Image Source Control IDs
     non-sensitive.
     This control is required for automatic calibration of sensors/cameras.
 
+``V4L2_CID_VTOTAL (integer)``
+    Number of total lines per frame, including data and idle lines (blanking).
+    The unit of the vertical total size is a line. Every line has length of the
+    image width plus horizontal blanking at the pixel rate defined by
+    ``V4L2_CID_PIXEL_RATE`` control in the same sub-device.
+
 .. c:type:: v4l2_area
 
 .. flat-table:: struct v4l2_area
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
index 564fedee2c88..6a0d310d5f42 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
@@ -1112,6 +1112,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_TEST_PATTERN_BLUE:	return "Blue Pixel Value";
 	case V4L2_CID_TEST_PATTERN_GREENB:	return "Green (Blue) Pixel Value";
 	case V4L2_CID_NOTIFY_GAINS:		return "Notify Gains";
+	case V4L2_CID_VTOTAL:			return "Vertical Total Size";
 
 	/* Image processing controls */
 	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 5e80daa4ffe0..99120005634e 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -1117,6 +1117,7 @@ enum v4l2_jpeg_chroma_subsampling {
 #define V4L2_CID_TEST_PATTERN_GREENB		(V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 7)
 #define V4L2_CID_UNIT_CELL_SIZE			(V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 8)
 #define V4L2_CID_NOTIFY_GAINS			(V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 9)
+#define V4L2_CID_VTOTAL				(V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 10)
 
 
 /* Image processing controls */

-- 
2.34.1