vidioc-enum-freq-bands.rst

  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.