1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_G_FREQUENCY:
5
6 ********************************************
7 ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
8 ********************************************
9
10 Name
11 ====
12
13 VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_G_FREQUENCY
19
20 ``int ioctl(int fd, VIDIOC_G_FREQUENCY, struct v4l2_frequency *argp)``
21
22 .. c:macro:: VIDIOC_S_FREQUENCY
23
24 ``int ioctl(int fd, VIDIOC_S_FREQUENCY, const struct v4l2_frequency *argp)``
25
26 Arguments
27 =========
28
29 ``fd``
30 File descriptor returned by :c:func:`open()`.
31
32 ``argp``
33 Pointer to struct :c:type:`v4l2_frequency`.
34
35 Description
36 ===========
37
38 To get the current tuner or modulator radio frequency applications set
39 the ``tuner`` field of a struct
40 :c:type:`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.
45
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 :c:type:`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.
53
54 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
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 * - __u32
64 - ``tuner``
65 - The tuner or modulator index number. This is the same value as in
66 the struct :c:type:`v4l2_input` ``tuner`` field and
67 the struct :c:type:`v4l2_tuner` ``index`` field, or
68 the struct :c:type:`v4l2_output` ``modulator`` field
69 and the struct :c:type:`v4l2_modulator` ``index``
70 field.
71 * - __u32
72 - ``type``
73 - The tuner type. This is the same value as in the struct
74 :c:type:`v4l2_tuner` ``type`` field. The type must be
75 set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
76 to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
77 ``V4L2_TUNER_RADIO`` for modulators (currently only radio
78 modulators are supported). See :c:type:`v4l2_tuner_type`
79 * - __u32
80 - ``frequency``
81 - Tuning frequency in units of 62.5 kHz, or if the struct
82 :c:type:`v4l2_tuner` or struct
83 :c:type:`v4l2_modulator` ``capability`` flag
84 ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
85 used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
86 * - __u32
87 - ``reserved``\ [8]
88 - Reserved for future extensions. Drivers and applications must set
89 the array to zero.
90
91 Return Value
92 ============
93
94 On success 0 is returned, on error -1 and the ``errno`` variable is set
95 appropriately. The generic error codes are described at the
96 :ref:`Generic Error Codes <gen-errors>` chapter.
97
98 EINVAL
99 The ``tuner`` index is out of bounds or the value in the ``type``
100 field is wrong.
101
102 EBUSY
103 A hardware seek is in progress.
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