Document V4L2 selection targets that will be used to ROI
implementation.
Signed-off-by: Sergey Senozhatsky <senozhat...@chromium.org>
---
.../media/v4l/selection-api-configuration.rst | 22 +++++++++++++++
.../media/v4l/selection-api-examples.rst | 28 +++++++++++++++++++
.../media/v4l/v4l2-selection-targets.rst | 24 ++++++++++++++++
3 files changed, 74 insertions(+)
diff --git
a/Documentation/userspace-api/media/v4l/selection-api-configuration.rst
b/Documentation/userspace-api/media/v4l/selection-api-configuration.rst
index fee49bf1a1c0..b5fdd765e2db 100644
--- a/Documentation/userspace-api/media/v4l/selection-api-configuration.rst
+++ b/Documentation/userspace-api/media/v4l/selection-api-configuration.rst
@@ -135,3 +135,25 @@ and the height of rectangles obtained using
``V4L2_SEL_TGT_CROP`` and
``V4L2_SEL_TGT_COMPOSE`` targets. If these are not equal then the
scaling is applied. The application can compute the scaling ratios using
these values.
+
+Configuration of Region of Interest (ROI)
+=========================================
+
+The range of auto-controls values and of coordinates of the top left
+corner, width and height of areas that can be ROI is given by the
+``V4L2_SEL_TGT_ROI_BOUNDS_MIN`` and ``V4L2_SEL_TGT_ROI_BOUNDS_MAX``
+targets. It is recommended for the driver developers to put the top/left
+corner at position ``(0,0)``.
+
+The top left corner, width and height of the Region of Interest area
+and auto-controls currently being employed by the device are given by
+the ``V4L2_SEL_TGT_ROI`` target. It uses the same coordinate system
+as ``V4L2_SEL_TGT_ROI_BOUNDS_MIN`` and ``V4L2_SEL_TGT_ROI_BOUNDS_MAX``.
+
+In order to change active ROI top left, width and height coordinates
+and ROI auto-controls use ``V4L2_SEL_TGT_ROI`` target.
+
+Each capture device has a default ROI rectangle and auto-controls
+value given by the ``V4L2_SEL_TGT_ROI_DEFAULT`` target. Drivers shall
+set the ROI rectangle to the default when the driver is first loaded,
+but not later.
diff --git a/Documentation/userspace-api/media/v4l/selection-api-examples.rst
b/Documentation/userspace-api/media/v4l/selection-api-examples.rst
index 5f8e8a1f59d7..ad2664888700 100644
--- a/Documentation/userspace-api/media/v4l/selection-api-examples.rst
+++ b/Documentation/userspace-api/media/v4l/selection-api-examples.rst
@@ -82,3 +82,31 @@ Example: Querying for scaling factors
/* computing scaling factors */
hscale = (double)compose.r.width / crop.r.width;
vscale = (double)compose.r.height / crop.r.height;
+
+Setting Region Of Interest area to half of the default value
+
+Example: Simple ROI
+===========================
+
+.. code-block:: c
+
+ struct v4l2_selection roi = {
+ .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
+ .target = V4L2_SEL_TGT_ROI_DEFAULT,
+ };
+ struct v4l2_rect r;
+
+ ret = ioctl(fd, VIDIOC_G_SELECTION, &roi);
+ if (ret)
+ exit(-1);
+ /* setting smaller ROI rectangle */
+ r.width = roi.r.width / 2;
+ r.height = roi.r.height / 2;
+ r.left = roi.r.width / 4;
+ r.top = roi.r.height / 4;
+ roi.r = r;
+ roi.target = V4L2_SEL_TGT_ROI;
+ roi.flags = V4L2_SEL_FLAG_ROI_AUTO_EXPOSURE;
+ ret = ioctl(fd, VIDIOC_S_SELECTION, &roi);
+ if (ret)
+ exit(-1);
diff --git a/Documentation/userspace-api/media/v4l/v4l2-selection-targets.rst
b/Documentation/userspace-api/media/v4l/v4l2-selection-targets.rst
index b46bae984f35..d1dc9c50eb05 100644
--- a/Documentation/userspace-api/media/v4l/v4l2-selection-targets.rst
+++ b/Documentation/userspace-api/media/v4l/v4l2-selection-targets.rst
@@ -75,6 +75,30 @@ of the two interfaces they are used.
modified by hardware.
- Yes
- No
+ * - ``V4L2_SEL_TGT_ROI``
+ - 0x0200
+ - Current Region of Interest rectangle and auto-controls value.
+ - Yes
+ - No
+ * - ``V4L2_SEL_TGT_ROI_DEFAULT``
+ - 0x0201
+ - Suggested Region of Interest rectangle and auto-controls value.
+ - Yes
+ - No
+ * - ``V4L2_SEL_TGT_ROI_BOUNDS_MIN``
+ - 0x0202
+ - Minimum bounds of the Region of Interest rectangle and minimum
+ auto-controls value. All valid ROI rectangles and auto-controls
+ should be within minimum-maximum range.
+ - Yes
+ - No
+ * - ``V4L2_SEL_TGT_ROI_BOUNDS_MAX``
+ - 0x0203
+ - Maximum bounds of the Region of Interest rectangle and maximum
+ auto-controls value. All valid ROI rectangles and auto-controls
+ should be within minimum-maximum range.
+ - Yes
+ - No
.. raw:: latex
--
2.31.0.rc2.261.g7f71774620-goog
