vidioc-subdev-enum-frame-interval.rst

  1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
  2.. c:namespace:: V4L
  3
  4.. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
  5
  6***************************************
  7ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
  8***************************************
  9
 10Name
 11====
 12
 13VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals
 14
 15Synopsis
 16========
 17
 18.. c:macro:: VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
 19
 20``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp)``
 21
 22Arguments
 23=========
 24
 25``fd``
 26    File descriptor returned by :c:func:`open()`.
 27
 28``argp``
 29    Pointer to struct :c:type:`v4l2_subdev_frame_interval_enum`.
 30
 31Description
 32===========
 33
 34This ioctl lets applications enumerate available frame intervals on a
 35given sub-device pad. Frame intervals only makes sense for sub-devices
 36that can control the frame period on their own. This includes, for
 37instance, image sensors and TV tuners.
 38
 39For the common use case of image sensors, the frame intervals available
 40on the sub-device output pad depend on the frame format and size on the
 41same pad. Applications must thus specify the desired format and size
 42when enumerating frame intervals.
 43
 44To enumerate frame intervals applications initialize the ``index``,
 45``pad``, ``which``, ``code``, ``width`` and ``height`` fields of struct
 46:c:type:`v4l2_subdev_frame_interval_enum`
 47and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer
 48to this structure. Drivers fill the rest of the structure or return an
 49EINVAL error code if one of the input fields is invalid. All frame
 50intervals are enumerable by beginning at index zero and incrementing by
 51one until ``EINVAL`` is returned.
 52
 53Available frame intervals may depend on the current 'try' formats at
 54other pads of the sub-device, as well as on the current active links.
 55See :ref:`VIDIOC_SUBDEV_G_FMT` for more
 56information about the try formats.
 57
 58Sub-devices that support the frame interval enumeration ioctl should
 59implemented it on a single pad only. Its behaviour when supported on
 60multiple pads of the same sub-device is not defined.
 61
 62.. c:type:: v4l2_subdev_frame_interval_enum
 63
 64.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
 65
 66.. flat-table:: struct v4l2_subdev_frame_interval_enum
 67    :header-rows:  0
 68    :stub-columns: 0
 69    :widths:       1 1 2
 70
 71    * - __u32
 72      - ``index``
 73      - Number of the format in the enumeration, set by the application.
 74    * - __u32
 75      - ``pad``
 76      - Pad number as reported by the media controller API.
 77    * - __u32
 78      - ``code``
 79      - The media bus format code, as defined in
 80	:ref:`v4l2-mbus-format`.
 81    * - __u32
 82      - ``width``
 83      - Frame width, in pixels.
 84    * - __u32
 85      - ``height``
 86      - Frame height, in pixels.
 87    * - struct :c:type:`v4l2_fract`
 88      - ``interval``
 89      - Period, in seconds, between consecutive video frames.
 90    * - __u32
 91      - ``which``
 92      - Frame intervals to be enumerated, from enum
 93	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
 94    * - __u32
 95      - ``stream``
 96      - Stream identifier.
 97    * - __u32
 98      - ``reserved``\ [7]
 99      - Reserved for future extensions. Applications and drivers must set
100	the array to zero.
101
102Return Value
103============
104
105On success 0 is returned, on error -1 and the ``errno`` variable is set
106appropriately. The generic error codes are described at the
107:ref:`Generic Error Codes <gen-errors>` chapter.
108
109EINVAL
110    The struct :c:type:`v4l2_subdev_frame_interval_enum` ``pad`` references a
111    non-existing pad, the ``which`` field has an unsupported value, one of the
112    ``code``, ``width`` or ``height`` fields are invalid for the given pad, or
113    the ``index`` field is out of bounds.