tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_G_FREQUENCY:
5
6********************************************
7ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
8********************************************
9
10Name
11====
12
13VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
14
15Synopsis
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
26Arguments
27=========
28
29``fd``
30 File descriptor returned by :c:func:`open()`.
31
32``argp``
33 Pointer to struct :c:type:`v4l2_frequency`.
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.. 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
91Return Value
92============
93
94On success 0 is returned, on error -1 and the ``errno`` variable is set
95appropriately. The generic error codes are described at the
96:ref:`Generic Error Codes <gen-errors>` chapter.
97
98EINVAL
99 The ``tuner`` index is out of bounds or the value in the ``type``
100 field is wrong.
101
102EBUSY
103 A hardware seek is in progress.