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 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_subdev_frame_interval_enum * argp )
  19
  20
  21 Arguments
  22 =========
  23
  24 ``fd``
  25     File descriptor returned by :ref:`open() <func-open>`.
  26
  27 ``request``
  28     VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL
  29
  30 ``argp``
  31
  32
  33 Description
  34 ===========
  35
  36 This ioctl lets applications enumerate available frame intervals on a
  37 given sub-device pad. Frame intervals only makes sense for sub-devices
  38 that can control the frame period on their own. This includes, for
  39 instance, image sensors and TV tuners.
  40
  41 For the common use case of image sensors, the frame intervals available
  42 on the sub-device output pad depend on the frame format and size on the
  43 same pad. Applications must thus specify the desired format and size
  44 when enumerating frame intervals.
  45
  46 To enumerate frame intervals applications initialize the ``index``,
  47 ``pad``, ``which``, ``code``, ``width`` and ``height`` fields of struct
  48 :ref:`v4l2_subdev_frame_interval_enum <v4l2-subdev-frame-interval-enum>`
  49 and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer
  50 to this structure. Drivers fill the rest of the structure or return an
  51 EINVAL error code if one of the input fields is invalid. All frame
  52 intervals are enumerable by beginning at index zero and incrementing by
  53 one until ``EINVAL`` is returned.
  54
  55 Available frame intervals may depend on the current 'try' formats at
  56 other pads of the sub-device, as well as on the current active links.
  57 See :ref:`VIDIOC_SUBDEV_G_FMT` for more
  58 information about the try formats.
  59
  60 Sub-devices that support the frame interval enumeration ioctl should
  61 implemented it on a single pad only. Its behaviour when supported on
  62 multiple pads of the same sub-device is not defined.
  63
  64
  65 .. _v4l2-subdev-frame-interval-enum:
  66
  67 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
  68
  69 .. flat-table:: struct v4l2_subdev_frame_interval_enum
  70     :header-rows:  0
  71     :stub-columns: 0
  72     :widths:       1 1 2
  73
  74
  75     -  .. row 1
  76
  77        -  __u32
  78
  79        -  ``index``
  80
  81        -  Number of the format in the enumeration, set by the application.
  82
  83     -  .. row 2
  84
  85        -  __u32
  86
  87        -  ``pad``
  88
  89        -  Pad number as reported by the media controller API.
  90
  91     -  .. row 3
  92
  93        -  __u32
  94
  95        -  ``code``
  96
  97        -  The media bus format code, as defined in
  98           :ref:`v4l2-mbus-format`.
  99
 100     -  .. row 4
 101
 102        -  __u32
 103
 104        -  ``width``
 105
 106        -  Frame width, in pixels.
 107
 108     -  .. row 5
 109
 110        -  __u32
 111
 112        -  ``height``
 113
 114        -  Frame height, in pixels.
 115
 116     -  .. row 6
 117
 118        -  struct :ref:`v4l2_fract <v4l2-fract>`
 119
 120        -  ``interval``
 121
 122        -  Period, in seconds, between consecutive video frames.
 123
 124     -  .. row 7
 125
 126        -  __u32
 127
 128        -  ``which``
 129
 130        -  Frame intervals to be enumerated, from enum
 131           :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
 132
 133     -  .. row 8
 134
 135        -  __u32
 136
 137        -  ``reserved``\ [8]
 138
 139        -  Reserved for future extensions. Applications and drivers must set
 140           the array to zero.
 141
 142
 143 Return Value
 144 ============
 145
 146 On success 0 is returned, on error -1 and the ``errno`` variable is set
 147 appropriately. The generic error codes are described at the
 148 :ref:`Generic Error Codes <gen-errors>` chapter.
 149
 150 EINVAL
 151     The struct
 152     :ref:`v4l2_subdev_frame_interval_enum <v4l2-subdev-frame-interval-enum>`
 153     ``pad`` references a non-existing pad, one of the ``code``,
 154     ``width`` or ``height`` fields are invalid for the given pad or the
 155     ``index`` field is out of bounds.