1 .. -*- coding: utf-8; mode: rst -*-
3 .. _VIDIOC_G_FREQUENCY:
5 ********************************************
6 ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
7 ********************************************
12 VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
18 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_frequency *argp )
20 .. cpp:function:: int ioctl( int fd, int request, const struct v4l2_frequency *argp )
27 File descriptor returned by :ref:`open() <func-open>`.
30 VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
38 To get the current tuner or modulator radio frequency applications set
39 the ``tuner`` field of a struct
40 :ref:`v4l2_frequency <v4l2-frequency>` to the respective tuner or
41 modulator number (only input devices have tuners, only output devices
42 have modulators), zero out the ``reserved`` array and call the
43 :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this structure. The
44 driver stores the current frequency in the ``frequency`` field.
46 To change the current tuner or modulator radio frequency applications
47 initialize the ``tuner``, ``type`` and ``frequency`` fields, and the
48 ``reserved`` array of a struct :ref:`v4l2_frequency <v4l2-frequency>`
49 and call the :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this
50 structure. When the requested frequency is not possible the driver
51 assumes the closest possible value. However :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` is a
52 write-only ioctl, it does not return the actual new frequency.
57 .. flat-table:: struct v4l2_frequency
69 - The tuner or modulator index number. This is the same value as in
70 the struct :ref:`v4l2_input <v4l2-input>` ``tuner`` field and
71 the struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` field, or
72 the struct :ref:`v4l2_output <v4l2-output>` ``modulator`` field
73 and the struct :ref:`v4l2_modulator <v4l2-modulator>` ``index``
82 - The tuner type. This is the same value as in the struct
83 :ref:`v4l2_tuner <v4l2-tuner>` ``type`` field. The type must be
84 set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
85 to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
86 ``V4L2_TUNER_RADIO`` for modulators (currently only radio
87 modulators are supported). See :ref:`v4l2-tuner-type`
95 - Tuning frequency in units of 62.5 kHz, or if the struct
96 :ref:`v4l2_tuner <v4l2-tuner>` or struct
97 :ref:`v4l2_modulator <v4l2-modulator>` ``capability`` flag
98 ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
99 used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
107 - Reserved for future extensions. Drivers and applications must set
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.
119 The ``tuner`` index is out of bounds or the value in the ``type``
123 A hardware seek is in progress.