VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION — Get or set selection rectangles on a subdev pad
int ioctl( | int fd, |
| int request, | |
struct v4l2_subdev_selection *argp); |
fdFile descriptor returned by open().
requestVIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION
argpThis is an experimental interface and may change in the future.
The selections are used to configure various image processing functionality performed by the subdevs which affect the image size. This currently includes cropping, scaling and composition.
The selection API replaces the old subdev crop API. All the function of the crop API, and more, are supported by the selections API.
See the section called “Sub-device Interface” for more information on how each selection target affects the image processing pipeline inside the subdevice.
The are four types of selection targets: active, default, bounds and padding. The ACTIVE targets are the targets which configure the hardware. The BOUNDS target will return the maximum width and height of the target.
To discover which targets are supported, the user can
perform VIDIOC_SUBDEV_G_SELECTION on them.
Any unsupported target will return
EINVAL.
Table A.100. V4L2 subdev selection targets
V4L2_SUBDEV_SEL_TGT_CROP_ACTIVE | 0x0000 | Active crop. Defines the cropping performed by the processing step. |
V4L2_SUBDEV_SEL_TGT_CROP_BOUNDS | 0x0002 | Bounds of the crop rectangle. |
V4L2_SUBDEV_SEL_TGT_COMPOSE_ACTIVE | 0x0100 | Active compose rectangle. Used to configure scaling on sink pads and composition on source pads. |
V4L2_SUBDEV_SEL_TGT_COMPOSE_BOUNDS | 0x0102 | Bounds of the compose rectangle. |
Table A.101. V4L2 subdev selection flags
V4L2_SUBDEV_SEL_FLAG_SIZE_GE | (1 << 0) | Suggest the driver it should choose greater or equal rectangle (in size) than was requested. |
V4L2_SUBDEV_SEL_FLAG_SIZE_LE | (1 << 1) | Suggest the driver it should choose lesser or equal rectangle (in size) than was requested. |
V4L2_SUBDEV_SEL_FLAG_KEEP_CONFIG | (1 << 2) | The configuration should not be propagated to any further processing steps. If this flag is not given, the configuration is propagated inside the subdevice to all further processing steps. |
Table A.102. struct v4l2_subdev_selection
| __u32 | which | Active or try selection, from enum v4l2_subdev_format_whence. |
| __u32 | pad | Pad number as reported by the media framework. |
| __u32 | target | Target selection rectangle. See Table 4.19, “V4L2 subdev selection targets”. |
| __u32 | flags | Flags. See Table 4.20, “V4L2 subdev selection flags” |
| struct v4l2_rect | rect | Crop rectangle boundaries, in pixels. |
| __u32 | reserved[8] | Reserved for future extensions. Applications and drivers must set the array to zero. |
On success 0 is returned, on error -1 and the errno variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.
The selection rectangle can't be changed because the
pad is currently busy. This can be caused, for instance, by
an active video stream on the pad. The ioctl must not be
retried without performing another action to fix the problem
first. Only returned by
VIDIOC_SUBDEV_S_SELECTION
The struct v4l2_subdev_selection
pad references a non-existing
pad, the which field references a
non-existing format, or the selection target is not
supported on the given subdev pad.