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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_G_FREQUENCY:
+
+********************************************
+ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
+********************************************
+
+Name
+====
+
+VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct v4l2_frequency *argp )
+
+.. cpp:function:: int ioctl( int fd, int request, const struct v4l2_frequency *argp )
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``request``
+    VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
+
+``argp``
+
+
+Description
+===========
+
+To get the current tuner or modulator radio frequency applications set
+the ``tuner`` field of a struct
+:ref:`v4l2_frequency <v4l2-frequency>` to the respective tuner or
+modulator number (only input devices have tuners, only output devices
+have modulators), zero out the ``reserved`` array and call the
+:ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this structure. The
+driver stores the current frequency in the ``frequency`` field.
+
+To change the current tuner or modulator radio frequency applications
+initialize the ``tuner``, ``type`` and ``frequency`` fields, and the
+``reserved`` array of a struct :ref:`v4l2_frequency <v4l2-frequency>`
+and call the :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this
+structure. When the requested frequency is not possible the driver
+assumes the closest possible value. However :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` is a
+write-only ioctl, it does not return the actual new frequency.
+
+
+.. _v4l2-frequency:
+
+.. flat-table:: struct v4l2_frequency
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+
+    -  .. 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
+
+       -  ``frequency``
+
+       -  Tuning frequency in units of 62.5 kHz, or if the struct
+	  :ref:`v4l2_tuner <v4l2-tuner>` or struct
+	  :ref:`v4l2_modulator <v4l2-modulator>` ``capability`` flag
+	  ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
+	  used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
+
+    -  .. row 4
+
+       -  __u32
+
+       -  ``reserved``\ [8]
+
+       -  Reserved for future extensions. Drivers and applications must set
+	  the array to zero.
+
+
+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`` index is out of bounds or the value in the ``type``
+    field is wrong.
+
+EBUSY
+    A hardware seek is in progress.