v4.19.13 snapshot.
diff --git a/Documentation/media/uapi/v4l/selection-api-examples.rst b/Documentation/media/uapi/v4l/selection-api-examples.rst
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+.. -*- coding: utf-8; mode: rst -*-
+
+********
+Examples
+********
+
+(A video capture device is assumed; change
+``V4L2_BUF_TYPE_VIDEO_CAPTURE`` for other devices; change target to
+``V4L2_SEL_TGT_COMPOSE_*`` family to configure composing area)
+
+Example: Resetting the cropping parameters
+==========================================
+
+.. code-block:: c
+
+ struct v4l2_selection sel = {
+ .type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
+ .target = V4L2_SEL_TGT_CROP_DEFAULT,
+ };
+ ret = ioctl(fd, VIDIOC_G_SELECTION, &sel);
+ if (ret)
+ exit(-1);
+ sel.target = V4L2_SEL_TGT_CROP;
+ ret = ioctl(fd, VIDIOC_S_SELECTION, &sel);
+ if (ret)
+ exit(-1);
+
+Setting a composing area on output of size of *at most* half of limit
+placed at a center of a display.
+
+Example: Simple downscaling
+===========================
+
+.. code-block:: c
+
+ struct v4l2_selection sel = {
+ .type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
+ .target = V4L2_SEL_TGT_COMPOSE_BOUNDS,
+ };
+ struct v4l2_rect r;
+
+ ret = ioctl(fd, VIDIOC_G_SELECTION, &sel);
+ if (ret)
+ exit(-1);
+ /* setting smaller compose rectangle */
+ r.width = sel.r.width / 2;
+ r.height = sel.r.height / 2;
+ r.left = sel.r.width / 4;
+ r.top = sel.r.height / 4;
+ sel.r = r;
+ sel.target = V4L2_SEL_TGT_COMPOSE;
+ sel.flags = V4L2_SEL_FLAG_LE;
+ ret = ioctl(fd, VIDIOC_S_SELECTION, &sel);
+ if (ret)
+ exit(-1);
+
+A video output device is assumed; change ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
+for other devices
+
+Example: Querying for scaling factors
+=====================================
+
+.. code-block:: c
+
+ struct v4l2_selection compose = {
+ .type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
+ .target = V4L2_SEL_TGT_COMPOSE,
+ };
+ struct v4l2_selection crop = {
+ .type = V4L2_BUF_TYPE_VIDEO_OUTPUT,
+ .target = V4L2_SEL_TGT_CROP,
+ };
+ double hscale, vscale;
+
+ ret = ioctl(fd, VIDIOC_G_SELECTION, &compose);
+ if (ret)
+ exit(-1);
+ ret = ioctl(fd, VIDIOC_G_SELECTION, &crop);
+ if (ret)
+ exit(-1);
+
+ /* computing scaling factors */
+ hscale = (double)compose.r.width / crop.r.width;
+ vscale = (double)compose.r.height / crop.r.height;