vidioc-enum-freq-bands.rst (4414B)
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.