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);



File descriptor returned by open().






This 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.

Types of selection targets

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.

Discovering supported features

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_ACTIVE0x0000Active crop. Defines the cropping performed by the processing step.
V4L2_SUBDEV_SEL_TGT_CROP_BOUNDS0x0002Bounds of the crop rectangle.
V4L2_SUBDEV_SEL_TGT_COMPOSE_ACTIVE0x0100Active compose rectangle. Used to configure scaling on sink pads and composition on source pads.
V4L2_SUBDEV_SEL_TGT_COMPOSE_BOUNDS0x0102Bounds 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

__u32whichActive or try selection, from enum v4l2_subdev_format_whence.
__u32padPad number as reported by the media framework.
__u32targetTarget selection rectangle. See Table 4.19, “V4L2 subdev selection targets”.
__u32flagsFlags. See Table 4.20, “V4L2 subdev selection flags”
struct v4l2_rectrectCrop rectangle boundaries, in pixels.
__u32reserved[8]Reserved for future extensions. Applications and drivers must set the array to zero.

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.


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.