123 lines
3.6 KiB
ReStructuredText
123 lines
3.6 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
|
|
|
|
.. _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
|
|
========
|
|
|
|
.. cpp:function:: int ioctl( int fd, int request, struct v4l2_subdev_frame_interval *argp )
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
|
|
|
``request``
|
|
VIDIOC_SUBDEV_G_FRAME_INTERVAL,
|
|
VIDIOC_SUBDEV_S_FRAME_INTERVAL
|
|
|
|
``argp``
|
|
|
|
|
|
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
|
|
:ref:`v4l2_subdev_frame_interval <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
|
|
:ref:`v4l2_subdev_frame_interval <v4l2-subdev-frame-interval>`
|
|
contains the current frame interval as would be returned by a
|
|
``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
|
|
.. _v4l2-subdev-frame-interval:
|
|
|
|
.. flat-table:: struct v4l2_subdev_frame_interval
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
|
|
- .. row 1
|
|
|
|
- __u32
|
|
|
|
- ``pad``
|
|
|
|
- Pad number as reported by the media controller API.
|
|
|
|
- .. row 2
|
|
|
|
- struct :ref:`v4l2_fract <v4l2-fract>`
|
|
|
|
- ``interval``
|
|
|
|
- Period, in seconds, between consecutive video frames.
|
|
|
|
- .. row 3
|
|
|
|
- __u32
|
|
|
|
- ``reserved``\ [9]
|
|
|
|
- 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
|
|
:ref:`v4l2_subdev_frame_interval <v4l2-subdev-frame-interval>`
|
|
``pad`` references a non-existing pad, or the pad doesn't support
|
|
frame intervals.
|