VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL — Enumerate frame intervals
int ioctl( | int fd, |
| int request, | |
struct v4l2_subdev_frame_interval_enum *
argp); |
This is an experimental interface and may change in the future.
This ioctl lets applications enumerate available frame intervals on a given sub-device pad. Frame intervals only makes sense for sub-devices that can control the frame period on their own. This includes, for instance, image sensors and TV tuners.
For the common use case of image sensors, the frame intervals available on the sub-device output pad depend on the frame format and size on the same pad. Applications must thus specify the desired format and size when enumerating frame intervals.
To enumerate frame intervals applications initialize the
index, pad,
which, code,
width and height
fields of struct v4l2_subdev_frame_interval_enum and call the
VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL ioctl with a pointer
to this structure. Drivers fill the rest of the structure or return
an EINVAL error code if one of the input fields is invalid. All frame intervals are
enumerable by beginning at index zero and incrementing by one until
EINVAL is returned.
Available frame intervals may depend on the current 'try' formats
at other pads of the sub-device, as well as on the current active links. See
VIDIOC_SUBDEV_G_FMT for more information about the try formats.
Sub-devices that support the frame interval enumeration ioctl should implemented it on a single pad only. Its behaviour when supported on multiple pads of the same sub-device is not defined.
Table A.102. struct v4l2_subdev_frame_interval_enum
| __u32 | index | Number of the format in the enumeration, set by the application. |
| __u32 | pad | Pad number as reported by the media controller API. |
| __u32 | code | The media bus format code, as defined in the section called “Media Bus Formats”. |
| __u32 | width | Frame width, in pixels. |
| __u32 | height | Frame height, in pixels. |
| struct v4l2_fract | interval | Period, in seconds, between consecutive video frames. |
| __u32 | which | Frame intervals to be enumerated, from enum v4l2_subdev_format_whence. |
| __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 struct v4l2_subdev_frame_interval_enum
pad references a non-existing pad, one of
the code, width
or height fields are invalid for the given
pad or the index field is out of bounds.