VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP — Get or set the crop rectangle on a subdev pad
int ioctl( | int fd, |
| int request, | |
struct v4l2_subdev_crop *argp); |
int ioctl( | int fd, |
| int request, | |
const struct v4l2_subdev_crop *argp); |
This is an obsolete interface and may be removed in the future. It is superseded by the selection API.
To retrieve the current crop rectangle applications set the
pad field of a struct v4l2_subdev_crop to the
desired pad number as reported by the media API and the
which field to
V4L2_SUBDEV_FORMAT_ACTIVE. They then call the
VIDIOC_SUBDEV_G_CROP ioctl with a pointer to this
structure. The driver fills the members of the rect
field or returns EINVAL error code if the input arguments are invalid, or if cropping
is not supported on the given pad.
To change the current crop rectangle applications set both the
pad and which fields
and all members of the rect field. They then call
the VIDIOC_SUBDEV_S_CROP ioctl with a pointer to this
structure. The driver verifies the requested crop rectangle, adjusts it
based on the hardware capabilities and configures the device. Upon return
the struct v4l2_subdev_crop contains the current format as would be returned
by a VIDIOC_SUBDEV_G_CROP call.
Applications can query the device capabilities by setting the
which to
V4L2_SUBDEV_FORMAT_TRY. When set, 'try' crop
rectangles are not applied to the device by the driver, but are mangled
exactly as active crop rectangles and stored in the sub-device file handle.
Two applications querying the same sub-device would thus not interact with
each other.
Drivers must not return an error solely because the requested crop rectangle doesn't match the device capabilities. They must instead modify the rectangle to match what the hardware can provide. The modified format should be as close as possible to the original request.
Table A.105. struct v4l2_subdev_crop
| __u32 | pad | Pad number as reported by the media framework. |
| __u32 | which | Crop rectangle to get or set, from enum v4l2_subdev_format_whence. |
| 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 crop 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_CROP
The struct v4l2_subdev_crop pad
references a non-existing pad, the which
field references a non-existing format, or cropping is not supported
on the given subdev pad.