mirror of https://gitee.com/openkylin/linux.git
115 lines
3.7 KiB
ReStructuredText
115 lines
3.7 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
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.. document under the terms of the GNU Free Documentation License,
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.. Version 1.1 or any later version published by the Free Software
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.. Foundation, with no Invariant Sections, no Front-Cover Texts
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.. and no Back-Cover Texts. A copy of the license is included at
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.. Documentation/media/uapi/fdl-appendix.rst.
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..
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.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
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.. _VIDIOC_ENUM_DV_TIMINGS:
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***********************************************************
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ioctl VIDIOC_ENUM_DV_TIMINGS, VIDIOC_SUBDEV_ENUM_DV_TIMINGS
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***********************************************************
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Name
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====
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VIDIOC_ENUM_DV_TIMINGS - VIDIOC_SUBDEV_ENUM_DV_TIMINGS - Enumerate supported Digital Video timings
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_ENUM_DV_TIMINGS, struct v4l2_enum_dv_timings *argp )
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:name: VIDIOC_ENUM_DV_TIMINGS
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.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_ENUM_DV_TIMINGS, struct v4l2_enum_dv_timings *argp )
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:name: VIDIOC_SUBDEV_ENUM_DV_TIMINGS
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``argp``
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Pointer to struct :c:type:`v4l2_enum_dv_timings`.
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Description
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===========
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While some DV receivers or transmitters support a wide range of timings,
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others support only a limited number of timings. With this ioctl
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applications can enumerate a list of known supported timings. Call
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:ref:`VIDIOC_DV_TIMINGS_CAP` to check if it
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also supports other standards or even custom timings that are not in
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this list.
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To query the available timings, applications initialize the ``index``
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field, set the ``pad`` field to 0, zero the reserved array of struct
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:c:type:`v4l2_enum_dv_timings` and call the
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``VIDIOC_ENUM_DV_TIMINGS`` ioctl on a video node with a pointer to this
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structure. Drivers fill the rest of the structure or return an ``EINVAL``
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error code when the index is out of bounds. To enumerate all supported
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DV timings, applications shall begin at index zero, incrementing by one
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until the driver returns ``EINVAL``.
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.. note::
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Drivers may enumerate a different set of DV timings after
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switching the video input or output.
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When implemented by the driver DV timings of subdevices can be queried
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by calling the ``VIDIOC_SUBDEV_ENUM_DV_TIMINGS`` ioctl directly on a
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subdevice node. The DV timings are specific to inputs (for DV receivers)
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or outputs (for DV transmitters), applications must specify the desired
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pad number in the struct
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:c:type:`v4l2_enum_dv_timings` ``pad`` field.
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Attempts to enumerate timings on a pad that doesn't support them will
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return an ``EINVAL`` error code.
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.. c:type:: v4l2_enum_dv_timings
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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.. flat-table:: struct v4l2_enum_dv_timings
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:header-rows: 0
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:stub-columns: 0
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:widths: 1 1 2
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* - __u32
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- ``index``
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- Number of the DV timings, set by the application.
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* - __u32
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- ``pad``
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- Pad number as reported by the media controller API. This field is
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only used when operating on a subdevice node. When operating on a
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video node applications must set this field to zero.
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* - __u32
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- ``reserved``\ [2]
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- Reserved for future extensions. Drivers and applications must set
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the array to zero.
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* - struct :c:type:`v4l2_dv_timings`
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- ``timings``
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- The timings.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The struct :c:type:`v4l2_enum_dv_timings`
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``index`` is out of bounds or the ``pad`` number is invalid.
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ENODATA
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Digital video presets are not supported for this input or output.
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