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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
========
.. c:function:: int ioctl( int fd, VIDIOC_G_FREQUENCY, struct v4l2_frequency *argp )
:name: VIDIOC_G_FREQUENCY
.. c:function:: int ioctl( int fd, VIDIOC_S_FREQUENCY, const struct v4l2_frequency *argp )
:name: VIDIOC_S_FREQUENCY
Arguments
=========
``fd``
File descriptor returned by :ref:`open() <func-open>`.
``argp``
Pointer to struct :c:type:`v4l2_frequency`.
Description
===========
To get the current tuner or modulator radio frequency applications set
the ``tuner`` field of a struct
:c:type:`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 :c:type:`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.
.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
.. c:type:: v4l2_frequency
.. flat-table:: struct v4l2_frequency
:header-rows: 0
:stub-columns: 0
:widths: 1 1 2
* - __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
- ``frequency``
- Tuning frequency in units of 62.5 kHz, or if the struct
:c:type:`v4l2_tuner` or struct
:c:type:`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.
* - __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.
|
