123 lines
4.2 KiB
ReStructuredText
123 lines
4.2 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
|
|
.. c:namespace:: V4L
|
|
|
|
.. _VIDIOC_SUBDEV_G_FRAME_INTERVAL:
|
|
|
|
********************************************************************
|
|
ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL
|
|
********************************************************************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:macro:: VIDIOC_SUBDEV_G_FRAME_INTERVAL
|
|
|
|
``int ioctl(int fd, VIDIOC_SUBDEV_G_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp)``
|
|
|
|
.. c:macro:: VIDIOC_SUBDEV_S_FRAME_INTERVAL
|
|
|
|
``int ioctl(int fd, VIDIOC_SUBDEV_S_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp)``
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :c:func:`open()`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_subdev_frame_interval`.
|
|
|
|
Description
|
|
===========
|
|
|
|
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 ``pad``
|
|
field of a struct
|
|
:c:type:`v4l2_subdev_frame_interval` to
|
|
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 ``interval`` field.
|
|
|
|
To change the current frame interval applications set both the ``pad``
|
|
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
|
|
struct
|
|
:c:type:`v4l2_subdev_frame_interval`
|
|
contains the current frame interval as would be returned by a
|
|
``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call.
|
|
|
|
Calling ``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 ``-EPERM``.
|
|
|
|
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.
|
|
|
|
.. c:type:: v4l2_subdev_frame_interval
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
|
|
|
|
.. flat-table:: struct v4l2_subdev_frame_interval
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __u32
|
|
- ``pad``
|
|
- Pad number as reported by the media controller API.
|
|
* - struct :c:type:`v4l2_fract`
|
|
- ``interval``
|
|
- Period, in seconds, between consecutive video frames.
|
|
* - __u32
|
|
- ``stream``
|
|
- Stream identifier.
|
|
* - __u32
|
|
- ``reserved``\ [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
|
|
:ref:`Generic Error Codes <gen-errors>` chapter.
|
|
|
|
EBUSY
|
|
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
|
|
``VIDIOC_SUBDEV_S_FRAME_INTERVAL``
|
|
|
|
EINVAL
|
|
The struct
|
|
:c:type:`v4l2_subdev_frame_interval`
|
|
``pad`` references a non-existing pad, or the pad doesn't support
|
|
frame intervals.
|
|
|
|
EPERM
|
|
The ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl has been called on a read-only
|
|
subdevice.
|