1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_ENUM_FREQ_BANDS:
5
6****************************
7ioctl VIDIOC_ENUM_FREQ_BANDS
8****************************
9
10Name
11====
12
13VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands
14
15Synopsis
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
22Arguments
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
31Description
32===========
33
34Enumerates the frequency bands that a tuner or modulator supports. To do
35this applications initialize the ``tuner``, ``type`` and ``index``
36fields, 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
40This ioctl is supported if the ``V4L2_TUNER_CAP_FREQ_BANDS`` capability
41of 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
130Return Value
131============
132
133On success 0 is returned, on error -1 and the ``errno`` variable is set
134appropriately. The generic error codes are described at the
135:ref:`Generic Error Codes <gen-errors>` chapter.
136
137EINVAL
138    The ``tuner`` or ``index`` is out of bounds or the ``type`` field is
139    wrong.
140