114 lines
3.5 KiB
ReStructuredText
Executable file
114 lines
3.5 KiB
ReStructuredText
Executable file
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
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***************************************
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ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
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***************************************
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Name
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====
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VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp )
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:name: VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
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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_subdev_frame_interval_enum`.
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Description
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===========
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This ioctl lets applications enumerate available frame intervals on a
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given sub-device pad. Frame intervals only makes sense for sub-devices
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that can control the frame period on their own. This includes, for
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instance, image sensors and TV tuners.
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For the common use case of image sensors, the frame intervals available
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on the sub-device output pad depend on the frame format and size on the
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same pad. Applications must thus specify the desired format and size
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when enumerating frame intervals.
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To enumerate frame intervals applications initialize the ``index``,
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``pad``, ``which``, ``code``, ``width`` and ``height`` fields of struct
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:c:type:`v4l2_subdev_frame_interval_enum`
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and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer
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to this structure. Drivers fill the rest of the structure or return an
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EINVAL error code if one of the input fields is invalid. All frame
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intervals are enumerable by beginning at index zero and incrementing by
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one until ``EINVAL`` is returned.
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Available frame intervals may depend on the current 'try' formats at
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other pads of the sub-device, as well as on the current active links.
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See :ref:`VIDIOC_SUBDEV_G_FMT` for more
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information about the try formats.
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Sub-devices that support the frame interval enumeration ioctl should
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implemented it on a single pad only. Its behaviour when supported on
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multiple pads of the same sub-device is not defined.
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.. c:type:: v4l2_subdev_frame_interval_enum
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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.. flat-table:: struct v4l2_subdev_frame_interval_enum
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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 format in the enumeration, 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.
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* - __u32
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- ``code``
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- The media bus format code, as defined in
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:ref:`v4l2-mbus-format`.
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* - __u32
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- ``width``
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- Frame width, in pixels.
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* - __u32
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- ``height``
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- Frame height, in pixels.
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* - struct :c:type:`v4l2_fract`
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- ``interval``
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- Period, in seconds, between consecutive video frames.
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* - __u32
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- ``which``
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- Frame intervals to be enumerated, from enum
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:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
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* - __u32
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- ``reserved``\ [8]
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- Reserved for future extensions. Applications and drivers must set
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the array to zero.
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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
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:c:type:`v4l2_subdev_frame_interval_enum`
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``pad`` references a non-existing pad, one of the ``code``,
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``width`` or ``height`` fields are invalid for the given pad or the
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``index`` field is out of bounds.
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