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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_ENUM_FREQ_BANDS:
+
+****************************
+ioctl VIDIOC_ENUM_FREQ_BANDS
+****************************
+
+Name
+====
+
+VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct v4l2_frequency_band *argp )
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``request``
+ VIDIOC_ENUM_FREQ_BANDS
+
+``argp``
+
+
+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
+:ref:`v4l2_frequency_band <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.
+
+
+.. _v4l2-frequency-band:
+
+.. flat-table:: struct v4l2_frequency_band
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2 1 1
+
+
+ - .. row 1
+
+ - __u32
+
+ - ``tuner``
+
+ - The tuner or modulator index number. This is the same value as in
+ the struct :ref:`v4l2_input <v4l2-input>` ``tuner`` field and
+ the struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` field, or
+ the struct :ref:`v4l2_output <v4l2-output>` ``modulator`` field
+ and the struct :ref:`v4l2_modulator <v4l2-modulator>` ``index``
+ field.
+
+ - .. row 2
+
+ - __u32
+
+ - ``type``
+
+ - The tuner type. This is the same value as in the struct
+ :ref:`v4l2_tuner <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 :ref:`v4l2-tuner-type`
+
+ - .. row 3
+
+ - __u32
+
+ - ``index``
+
+ - Identifies the frequency band, set by the application.
+
+ - .. row 4
+
+ - __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.
+
+ - .. row 5
+
+ - __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.
+
+ - .. row 6
+
+ - __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.
+
+ - .. row 7
+
+ - __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.
+
+ - .. row 8
+
+ - __u32
+
+ - ``reserved``\ [9]
+
+ - Reserved for future extensions. Applications and drivers must set
+ the array to zero.
+
+
+
+.. _band-modulation:
+
+.. flat-table:: Band Modulation Systems
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+
+ - .. row 1
+
+ - ``V4L2_BAND_MODULATION_VSB``
+
+ - 0x02
+
+ - Vestigial Sideband modulation, used for analog TV.
+
+ - .. row 2
+
+ - ``V4L2_BAND_MODULATION_FM``
+
+ - 0x04
+
+ - Frequency Modulation, commonly used for analog radio.
+
+ - .. row 3
+
+ - ``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.