mirror of https://gitee.com/openkylin/linux.git
121 lines
3.9 KiB
ReStructuredText
121 lines
3.9 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
|
|
.. document under the terms of the GNU Free Documentation License,
|
|
.. Version 1.1 or any later version published by the Free Software
|
|
.. Foundation, with no Invariant Sections, no Front-Cover Texts
|
|
.. and no Back-Cover Texts. A copy of the license is included at
|
|
.. Documentation/userspace-api/media/fdl-appendix.rst.
|
|
..
|
|
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
|
|
|
|
.. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
|
|
|
|
***************************************
|
|
ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
|
|
***************************************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals
|
|
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp )
|
|
:name: VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_subdev_frame_interval_enum`.
|
|
|
|
|
|
Description
|
|
===========
|
|
|
|
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
|
|
:c:type:`v4l2_subdev_frame_interval_enum`
|
|
and call the :ref:`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 :ref:`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.
|
|
|
|
.. c:type:: v4l2_subdev_frame_interval_enum
|
|
|
|
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
|
|
|
|
.. flat-table:: struct v4l2_subdev_frame_interval_enum
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2
|
|
|
|
* - __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
|
|
:ref:`v4l2-mbus-format`.
|
|
* - __u32
|
|
- ``width``
|
|
- Frame width, in pixels.
|
|
* - __u32
|
|
- ``height``
|
|
- Frame height, in pixels.
|
|
* - struct :c:type:`v4l2_fract`
|
|
- ``interval``
|
|
- Period, in seconds, between consecutive video frames.
|
|
* - __u32
|
|
- ``which``
|
|
- Frame intervals to be enumerated, from enum
|
|
:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
|
|
* - __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.
|
|
|
|
EINVAL
|
|
The struct
|
|
:c:type:`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.
|