106 lines
3.3 KiB
ReStructuredText
106 lines
3.3 KiB
ReStructuredText
.. -*- 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.
|