1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_ENUM_FREQ_BANDS:
5
6 ****************************
7 ioctl VIDIOC_ENUM_FREQ_BANDS
8 ****************************
9
10 Name
11 ====
12
13 VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands
14
15 Synopsis
16 ========
17
18 .. c:macro:: VIDIOC_ENUM_FREQ_BANDS
19
20 ``int ioctl(int fd, VIDIOC_ENUM_FREQ_BANDS, struct v4l2_frequency_band *argp)``
21
22 Arguments
23 =========
24
25 ``fd``
26 File descriptor returned by :c:func:`open()`.
27
28 ``argp``
29 Pointer to struct :c:type:`v4l2_frequency_band`.
30
31 Description
32 ===========
33
34 Enumerates the frequency bands that a tuner or modulator supports. To do
35 this applications initialize the ``tuner``, ``type`` and ``index``
36 fields, and zero out the ``reserved`` array of a struct
37 :c:type:`v4l2_frequency_band` and call the
38 :ref:`VIDIOC_ENUM_FREQ_BANDS` ioctl with a pointer to this structure.
39
40 This ioctl is supported if the ``V4L2_TUNER_CAP_FREQ_BANDS`` capability
41 of the corresponding tuner/modulator is set.
42
43 .. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{2.4cm}|
44
45 .. c:type:: v4l2_frequency_band
46
47 .. flat-table:: struct v4l2_frequency_band
48 :header-rows: 0
49 :stub-columns: 0
50 :widths: 1 1 2 1 1
51
52 * - __u32
53 - ``tuner``
54 - The tuner or modulator index number. This is the same value as in
55 the struct :c:type:`v4l2_input` ``tuner`` field and
56 the struct :c:type:`v4l2_tuner` ``index`` field, or
57 the struct :c:type:`v4l2_output` ``modulator`` field
58 and the struct :c:type:`v4l2_modulator` ``index``
59 field.
60 * - __u32
61 - ``type``
62 - The tuner type. This is the same value as in the struct
63 :c:type:`v4l2_tuner` ``type`` field. The type must be
64 set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
65 to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
66 ``V4L2_TUNER_RADIO`` for modulators (currently only radio
67 modulators are supported). See :c:type:`v4l2_tuner_type`
68 * - __u32
69 - ``index``
70 - Identifies the frequency band, set by the application.
71 * - __u32
72 - ``capability``
73 - :cspan:`2` The tuner/modulator capability flags for this
74 frequency band, see :ref:`tuner-capability`. The
75 ``V4L2_TUNER_CAP_LOW`` or ``V4L2_TUNER_CAP_1HZ`` capability must
76 be the same for all frequency bands of the selected
77 tuner/modulator. So either all bands have that capability set, or
78 none of them have that capability.
79 * - __u32
80 - ``rangelow``
81 - :cspan:`2` The lowest tunable frequency in units of 62.5 kHz, or
82 if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units
83 of 62.5 Hz, for this frequency band. A 1 Hz unit is used when the
84 ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
85 * - __u32
86 - ``rangehigh``
87 - :cspan:`2` The highest tunable frequency in units of 62.5 kHz,
88 or if the ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in
89 units of 62.5 Hz, for this frequency band. A 1 Hz unit is used
90 when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
91 * - __u32
92 - ``modulation``
93 - :cspan:`2` The supported modulation systems of this frequency
94 band. See :ref:`band-modulation`.
95
96 .. note::
97
98 Currently only one modulation system per frequency band
99 is supported. More work will need to be done if multiple
100 modulation systems are possible. Contact the linux-media
101 mailing list
102 (`https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__)
103 if you need such functionality.
104 * - __u32
105 - ``reserved``\ [9]
106 - Reserved for future extensions.
107
108 Applications and drivers must set the array to zero.
109
110
111 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
112
113 .. _band-modulation:
114
115 .. flat-table:: Band Modulation Systems
116 :header-rows: 0
117 :stub-columns: 0
118 :widths: 3 1 4
119
120 * - ``V4L2_BAND_MODULATION_VSB``
121 - 0x02
122 - Vestigial Sideband modulation, used for analog TV.
123 * - ``V4L2_BAND_MODULATION_FM``
124 - 0x04
125 - Frequency Modulation, commonly used for analog radio.
126 * - ``V4L2_BAND_MODULATION_AM``
127 - 0x08
128 - Amplitude Modulation, commonly used for analog radio.
129
130 Return Value
131 ============
132
133 On success 0 is returned, on error -1 and the ``errno`` variable is set
134 appropriately. The generic error codes are described at the
135 :ref:`Generic Error Codes <gen-errors>` chapter.
136
137 EINVAL
138 The ``tuner`` or ``index`` is out of bounds or the ``type`` field is
139 wrong.
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