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diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-freq-bands.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-freq-bands.rst new file mode 100644 index 000000000..e385929be --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-freq-bands.rst @@ -0,0 +1,139 @@ +.. 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. |