vidioc-g-frequency.rst

.. -*- coding: utf-8; mode: rst -*-

.. _vidioc-g-frequency:

********************************************
ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
********************************************

*man VIDIOC_G_FREQUENCY(2)*

VIDIOC_S_FREQUENCY
Get or set tuner or modulator radio frequency


Synopsis
========

.. c:function:: int ioctl( int fd, int request, struct v4l2_frequency *argp )

.. c: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
``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 ``VIDIOC_S_FREQUENCY`` ioctl with a pointer to this
structure. When the requested frequency is not possible the driver
assumes the closest possible value. However ``VIDIOC_S_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.


.. ------------------------------------------------------------------------------
.. This file was automatically converted from DocBook-XML with the dbxml
.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
.. from the linux kernel, refer to:
..
.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
.. ------------------------------------------------------------------------------