Documentation/linux_tv/media/v4l/vidioc-g-frequency.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_G_FREQUENCY:
   4
   5 ********************************************
   6 ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
   7 ********************************************
   8
   9 *man VIDIOC_G_FREQUENCY(2)*
  10
  11 VIDIOC_S_FREQUENCY
  12 Get or set tuner or modulator radio frequency
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. c:function:: int ioctl( int fd, int request, struct v4l2_frequency *argp )
  19
  20 .. c:function:: int ioctl( int fd, int request, const struct v4l2_frequency *argp )
  21
  22 Arguments
  23 =========
  24
  25 ``fd``
  26     File descriptor returned by :ref:`open() <func-open>`.
  27
  28 ``request``
  29     VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
  30
  31 ``argp``
  32
  33
  34 Description
  35 ===========
  36
  37 To get the current tuner or modulator radio frequency applications set
  38 the ``tuner`` field of a struct
  39 :ref:`v4l2_frequency <v4l2-frequency>` to the respective tuner or
  40 modulator number (only input devices have tuners, only output devices
  41 have modulators), zero out the ``reserved`` array and call the
  42 :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this structure. The
  43 driver stores the current frequency in the ``frequency`` field.
  44
  45 To change the current tuner or modulator radio frequency applications
  46 initialize the ``tuner``, ``type`` and ``frequency`` fields, and the
  47 ``reserved`` array of a struct :ref:`v4l2_frequency <v4l2-frequency>`
  48 and call the :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this
  49 structure. When the requested frequency is not possible the driver
  50 assumes the closest possible value. However :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` is a
  51 write-only ioctl, it does not return the actual new frequency.
  52
  53
  54 .. _v4l2-frequency:
  55
  56 .. flat-table:: struct v4l2_frequency
  57     :header-rows:  0
  58     :stub-columns: 0
  59     :widths:       1 1 2
  60
  61
  62     -  .. row 1
  63
  64        -  __u32
  65
  66        -  ``tuner``
  67
  68        -  The tuner or modulator index number. This is the same value as in
  69           the struct :ref:`v4l2_input <v4l2-input>` ``tuner`` field and
  70           the struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` field, or
  71           the struct :ref:`v4l2_output <v4l2-output>` ``modulator`` field
  72           and the struct :ref:`v4l2_modulator <v4l2-modulator>` ``index``
  73           field.
  74
  75     -  .. row 2
  76
  77        -  __u32
  78
  79        -  ``type``
  80
  81        -  The tuner type. This is the same value as in the struct
  82           :ref:`v4l2_tuner <v4l2-tuner>` ``type`` field. The type must be
  83           set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
  84           to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
  85           ``V4L2_TUNER_RADIO`` for modulators (currently only radio
  86           modulators are supported). See :ref:`v4l2-tuner-type`
  87
  88     -  .. row 3
  89
  90        -  __u32
  91
  92        -  ``frequency``
  93
  94        -  Tuning frequency in units of 62.5 kHz, or if the struct
  95           :ref:`v4l2_tuner <v4l2-tuner>` or struct
  96           :ref:`v4l2_modulator <v4l2-modulator>` ``capability`` flag
  97           ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
  98           used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
  99
 100     -  .. row 4
 101
 102        -  __u32
 103
 104        -  ``reserved``\ [8]
 105
 106        -  Reserved for future extensions. Drivers and applications must set
 107           the array to zero.
 108
 109
 110
 111 Return Value
 112 ============
 113
 114 On success 0 is returned, on error -1 and the ``errno`` variable is set
 115 appropriately. The generic error codes are described at the
 116 :ref:`Generic Error Codes <gen-errors>` chapter.
 117
 118 EINVAL
 119     The ``tuner`` index is out of bounds or the value in the ``type``
 120     field is wrong.
 121
 122 EBUSY
 123     A hardware seek is in progress.
 124
 125
 126 .. ------------------------------------------------------------------------------
 127 .. This file was automatically converted from DocBook-XML with the dbxml
 128 .. library (https://github.com/return42/sphkerneldoc). The origin XML comes
 129 .. from the linux kernel, refer to:
 130 ..
 131 .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
 132 .. ------------------------------------------------------------------------------