7.58. ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP

7.58.1. Name

VIDIOC_SUBDEV_G_CROP - VIDIOC_SUBDEV_S_CROP - Get or set the crop rectangle on a subdev pad

7.58.2. Synopsis

VIDIOC_SUBDEV_G_CROP

int ioctl(int fd, VIDIOC_SUBDEV_G_CROP, struct v4l2_subdev_crop *argp)

VIDIOC_SUBDEV_S_CROP

int ioctl(int fd, VIDIOC_SUBDEV_S_CROP, const struct v4l2_subdev_crop *argp)

7.58.3. Arguments

fd

File descriptor returned by open().

argp

Pointer to struct v4l2_subdev_crop.

7.58.4. Description

Note

This is an Obsolete API Elements 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 It is superseded by the selection API.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.

If the subdev device node has been registered in read-only mode, calls to VIDIOC_SUBDEV_S_CROP are only valid if the which field is set to V4L2_SUBDEV_FORMAT_TRY, otherwise an error is returned and the errno variable is set to -EPERM.

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.

type v4l2_subdev_crop

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.

7.58.5. Return Value

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.

EBUSY

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

EINVAL

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.

EPERM

The VIDIOC_SUBDEV_S_CROP ioctl has been called on a read-only subdevice and the which field is set to V4L2_SUBDEV_FORMAT_ACTIVE.