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