Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL:
   4
   5 ***************************************
   6 ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
   7 ***************************************
   8
   9 Name
  10 ====
  11
  12 VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp )
  19     :name: VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
  20
  21
  22 Arguments
  23 =========
  24
  25 ``fd``
  26     File descriptor returned by :ref:`open() <func-open>`.
  27
  28 ``argp``
  29
  30
  31 Description
  32 ===========
  33
  34 This ioctl lets applications enumerate available frame intervals on a
  35 given sub-device pad. Frame intervals only makes sense for sub-devices
  36 that can control the frame period on their own. This includes, for
  37 instance, image sensors and TV tuners.
  38
  39 For the common use case of image sensors, the frame intervals available
  40 on the sub-device output pad depend on the frame format and size on the
  41 same pad. Applications must thus specify the desired format and size
  42 when enumerating frame intervals.
  43
  44 To 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`
  47 and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer
  48 to this structure. Drivers fill the rest of the structure or return an
  49 EINVAL error code if one of the input fields is invalid. All frame
  50 intervals are enumerable by beginning at index zero and incrementing by
  51 one until ``EINVAL`` is returned.
  52
  53 Available frame intervals may depend on the current 'try' formats at
  54 other pads of the sub-device, as well as on the current active links.
  55 See :ref:`VIDIOC_SUBDEV_G_FMT` for more
  56 information about the try formats.
  57
  58 Sub-devices that support the frame interval enumeration ioctl should
  59 implemented it on a single pad only. Its behaviour when supported on
  60 multiple 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{8.7cm}|
  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
  72     -  .. row 1
  73
  74        -  __u32
  75
  76        -  ``index``
  77
  78        -  Number of the format in the enumeration, set by the application.
  79
  80     -  .. row 2
  81
  82        -  __u32
  83
  84        -  ``pad``
  85
  86        -  Pad number as reported by the media controller API.
  87
  88     -  .. row 3
  89
  90        -  __u32
  91
  92        -  ``code``
  93
  94        -  The media bus format code, as defined in
  95           :ref:`v4l2-mbus-format`.
  96
  97     -  .. row 4
  98
  99        -  __u32
 100
 101        -  ``width``
 102
 103        -  Frame width, in pixels.
 104
 105     -  .. row 5
 106
 107        -  __u32
 108
 109        -  ``height``
 110
 111        -  Frame height, in pixels.
 112
 113     -  .. row 6
 114
 115        -  struct :c:type:`v4l2_fract`
 116
 117        -  ``interval``
 118
 119        -  Period, in seconds, between consecutive video frames.
 120
 121     -  .. row 7
 122
 123        -  __u32
 124
 125        -  ``which``
 126
 127        -  Frame intervals to be enumerated, from enum
 128           :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
 129
 130     -  .. row 8
 131
 132        -  __u32
 133
 134        -  ``reserved``\ [8]
 135
 136        -  Reserved for future extensions. Applications and drivers must set
 137           the array to zero.
 138
 139
 140 Return Value
 141 ============
 142
 143 On success 0 is returned, on error -1 and the ``errno`` variable is set
 144 appropriately. The generic error codes are described at the
 145 :ref:`Generic Error Codes <gen-errors>` chapter.
 146
 147 EINVAL
 148     The struct
 149     :c:type:`v4l2_subdev_frame_interval_enum`
 150     ``pad`` references a non-existing pad, one of the ``code``,
 151     ``width`` or ``height`` fields are invalid for the given pad or the
 152     ``index`` field is out of bounds.