Documentation/media/uapi/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 Name
  10 ====
  11
  12 VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. c:function:: int ioctl( int fd, VIDIOC_G_FREQUENCY, struct v4l2_frequency *argp )
  19     :name: VIDIOC_G_FREQUENCY
  20
  21 .. c:function:: int ioctl( int fd, VIDIOC_S_FREQUENCY, const struct v4l2_frequency *argp )
  22     :name: VIDIOC_S_FREQUENCY
  23
  24
  25 Arguments
  26 =========
  27
  28 ``fd``
  29     File descriptor returned by :ref:`open() <func-open>`.
  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 :c:type:`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 :c:type:`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 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
  55
  56 .. c:type:: v4l2_frequency
  57
  58 .. flat-table:: struct v4l2_frequency
  59     :header-rows:  0
  60     :stub-columns: 0
  61     :widths:       1 1 2
  62
  63
  64     -  .. row 1
  65
  66        -  __u32
  67
  68        -  ``tuner``
  69
  70        -  The tuner or modulator index number. This is the same value as in
  71           the struct :c:type:`v4l2_input` ``tuner`` field and
  72           the struct :c:type:`v4l2_tuner` ``index`` field, or
  73           the struct :c:type:`v4l2_output` ``modulator`` field
  74           and the struct :c:type:`v4l2_modulator` ``index``
  75           field.
  76
  77     -  .. row 2
  78
  79        -  __u32
  80
  81        -  ``type``
  82
  83        -  The tuner type. This is the same value as in the struct
  84           :c:type:`v4l2_tuner` ``type`` field. The type must be
  85           set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
  86           to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
  87           ``V4L2_TUNER_RADIO`` for modulators (currently only radio
  88           modulators are supported). See :c:type:`v4l2_tuner_type`
  89
  90     -  .. row 3
  91
  92        -  __u32
  93
  94        -  ``frequency``
  95
  96        -  Tuning frequency in units of 62.5 kHz, or if the struct
  97           :c:type:`v4l2_tuner` or struct
  98           :c:type:`v4l2_modulator` ``capability`` flag
  99           ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
 100           used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
 101
 102     -  .. row 4
 103
 104        -  __u32
 105
 106        -  ``reserved``\ [8]
 107
 108        -  Reserved for future extensions. Drivers and applications must set
 109           the array to zero.
 110
 111
 112 Return Value
 113 ============
 114
 115 On success 0 is returned, on error -1 and the ``errno`` variable is set
 116 appropriately. The generic error codes are described at the
 117 :ref:`Generic Error Codes <gen-errors>` chapter.
 118
 119 EINVAL
 120     The ``tuner`` index is out of bounds or the value in the ``type``
 121     field is wrong.
 122
 123 EBUSY
 124     A hardware seek is in progress.