7.56. ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE

7.56.1. Name

VIDIOC_SUBDEV_ENUM_FRAME_SIZE - Enumerate media bus frame sizes

7.56.2. Synopsis

VIDIOC_SUBDEV_ENUM_FRAME_SIZE

int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_SIZE, struct v4l2_subdev_frame_size_enum * argp)

7.56.3. Arguments

fd

File descriptor returned by open().

argp

Pointer to struct v4l2_subdev_frame_size_enum.

7.56.4. Description

This ioctl allows applications to access the enumeration of frame sizes supported by a sub-device on the specified pad for the specified media bus format. Supported formats can be retrieved with the ioctl VIDIOC_SUBDEV_ENUM_MBUS_CODE ioctl.

The enumerations are defined by the driver, and indexed using the index field of the struct v4l2_subdev_frame_size_enum. Each pair of pad and code correspond to a separate enumeration. Each enumeration starts with the index of 0, and the lowest invalid index marks the end of the enumeration.

Therefore, to enumerate frame sizes allowed on the specified pad and using the specified mbus format, initialize the pad, which, and code fields to desired values, and set index to 0. Then call the ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE ioctl with a pointer to the structure.

A successful call will return with minimum and maximum frame sizes filled in. Repeat with increasing index until EINVAL is received. EINVAL means that either no more entries are available in the enumeration, or that an input parameter was invalid.

Sub-devices that only support discrete frame sizes (such as most sensors) will return one or more frame sizes with identical minimum and maximum values.

Not all possible sizes in given [minimum, maximum] ranges need to be supported. For instance, a scaler that uses a fixed-point scaling ratio might not be able to produce every frame size between the minimum and maximum values. Applications must use the VIDIOC_SUBDEV_S_FMT ioctl to try the sub-device for an exact supported frame size.

Available frame sizes may depend on the current ‘try’ formats at other pads of the sub-device, as well as on the current active links and the current values of V4L2 controls. See ioctl VIDIOC_SUBDEV_G_FMT, VIDIOC_SUBDEV_S_FMT for more information about try formats.

type v4l2_subdev_frame_size_enum

struct v4l2_subdev_frame_size_enum

__u32	index	Index of the frame size in the enumeration belonging to the given pad and format. Filled in by the application.
__u32	pad	Pad number as reported by the media controller API. Filled in by the application.
__u32	code	The media bus format code, as defined in Media Bus Formats. Filled in by the application.
__u32	min_width	Minimum frame width, in pixels. Filled in by the driver.
__u32	max_width	Maximum frame width, in pixels. Filled in by the driver.
__u32	min_height	Minimum frame height, in pixels. Filled in by the driver.
__u32	max_height	Maximum frame height, in pixels. Filled in by the driver.
__u32	which	Frame sizes to be enumerated, from enum v4l2_subdev_format_whence.
__u32	stream	Stream identifier.
__u32	reserved[7]	Reserved for future extensions. Applications and drivers must set the array to zero.

7.56.5. 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.

EINVAL

The struct v4l2_subdev_frame_size_enum pad references a non-existing pad, the which field has an unsupported value, the code is invalid for the given pad, or the index field is out of bounds.