7.60. ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL¶
VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad
These ioctls are used to get and set the frame interval at specific subdev pads in the image pipeline. The frame interval only makes sense for sub-devices that can control the frame period on their own. This includes, for instance, image sensors and TV tuners. Sub-devices that don’t support frame intervals must not implement these ioctls.
To retrieve the current frame interval applications set the
field of a struct
the desired pad number as reported by the media controller API. When
they call the
VIDIOC_SUBDEV_G_FRAME_INTERVAL ioctl with a pointer to
this structure the driver fills the members of the
To change the current frame interval applications set both the
field and all members of the
interval field. When they call the
VIDIOC_SUBDEV_S_FRAME_INTERVAL ioctl with a pointer to this
structure the driver verifies the requested interval, adjusts it based
on the hardware capabilities and configures the device. Upon return the
contains the current frame interval as would be returned by a
VIDIOC_SUBDEV_S_FRAME_INTERVAL on a subdev device node that has been
registered in read-only mode is not allowed. An error is returned and the errno
variable is set to
Drivers must not return an error solely because the requested interval doesn’t match the device capabilities. They must instead modify the interval to match what the hardware can provide. The modified interval should be as close as possible to the original request.
Changing the frame interval shall never change the format. Changing the format, on the other hand, may change the frame interval.
Sub-devices that support the frame interval ioctls should implement them on a single pad only. Their behaviour when supported on multiple pads of the same sub-device is not defined.
||Pad number as reported by the media controller API.|
||Period, in seconds, between consecutive video frames.|
||Reserved for future extensions. Applications and drivers must set the array to zero.|
7.60.5. 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.
- The frame interval 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
- The struct
padreferences a non-existing pad, or the pad doesn’t support frame intervals.
VIDIOC_SUBDEV_S_FRAME_INTERVALioctl has been called on a read-only subdevice.