1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3.. _VIDIOC_G_FREQUENCY:
4
5********************************************
6ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
7********************************************
8
9Name
10====
11
12VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
13
14
15Synopsis
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
25Arguments
26=========
27
28``fd``
29    File descriptor returned by :ref:`open() <func-open>`.
30
31``argp``
32    Pointer to struct :c:type:`v4l2_frequency`.
33
34
35Description
36===========
37
38To get the current tuner or modulator radio frequency applications set
39the ``tuner`` field of a struct
40:c:type:`v4l2_frequency` to the respective tuner or
41modulator number (only input devices have tuners, only output devices
42have 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
44driver stores the current frequency in the ``frequency`` field.
45
46To change the current tuner or modulator radio frequency applications
47initialize the ``tuner``, ``type`` and ``frequency`` fields, and the
48``reserved`` array of a struct :c:type:`v4l2_frequency`
49and call the :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this
50structure. When the requested frequency is not possible the driver
51assumes the closest possible value. However :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` is a
52write-only ioctl, it does not return the actual new frequency.
53
54
55.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
56
57.. c:type:: v4l2_frequency
58
59.. flat-table:: struct v4l2_frequency
60    :header-rows:  0
61    :stub-columns: 0
62    :widths:       1 1 2
63
64    * - __u32
65      - ``tuner``
66      - The tuner or modulator index number. This is the same value as in
67	the struct :c:type:`v4l2_input` ``tuner`` field and
68	the struct :c:type:`v4l2_tuner` ``index`` field, or
69	the struct :c:type:`v4l2_output` ``modulator`` field
70	and the struct :c:type:`v4l2_modulator` ``index``
71	field.
72    * - __u32
73      - ``type``
74      - The tuner type. This is the same value as in the struct
75	:c:type:`v4l2_tuner` ``type`` field. The type must be
76	set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
77	to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
78	``V4L2_TUNER_RADIO`` for modulators (currently only radio
79	modulators are supported). See :c:type:`v4l2_tuner_type`
80    * - __u32
81      - ``frequency``
82      - Tuning frequency in units of 62.5 kHz, or if the struct
83	:c:type:`v4l2_tuner` or struct
84	:c:type:`v4l2_modulator` ``capability`` flag
85	``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
86	used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
87    * - __u32
88      - ``reserved``\ [8]
89      - Reserved for future extensions. Drivers and applications must set
90	the array to zero.
91
92
93Return Value
94============
95
96On success 0 is returned, on error -1 and the ``errno`` variable is set
97appropriately. The generic error codes are described at the
98:ref:`Generic Error Codes <gen-errors>` chapter.
99
100EINVAL
101    The ``tuner`` index is out of bounds or the value in the ``type``
102    field is wrong.
103
104EBUSY
105    A hardware seek is in progress.
106