.. 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 `__) 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 ` chapter. EINVAL The ``tuner`` or ``index`` is out of bounds or the ``type`` field is wrong.