mirror of https://gitee.com/openkylin/linux.git
151 lines
4.7 KiB
ReStructuredText
151 lines
4.7 KiB
ReStructuredText
.. Permission is granted to copy, distribute and/or modify this
|
|
.. document under the terms of the GNU Free Documentation License,
|
|
.. Version 1.1 or any later version published by the Free Software
|
|
.. Foundation, with no Invariant Sections, no Front-Cover Texts
|
|
.. and no Back-Cover Texts. A copy of the license is included at
|
|
.. Documentation/media/uapi/fdl-appendix.rst.
|
|
..
|
|
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
|
|
|
|
.. _VIDIOC_ENUM_FREQ_BANDS:
|
|
|
|
****************************
|
|
ioctl VIDIOC_ENUM_FREQ_BANDS
|
|
****************************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands
|
|
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:function:: int ioctl( int fd, VIDIOC_ENUM_FREQ_BANDS, struct v4l2_frequency_band *argp )
|
|
:name: VIDIOC_ENUM_FREQ_BANDS
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_frequency_band`.
|
|
|
|
|
|
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
|
|
:c:type:`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.
|
|
|
|
|
|
.. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{3.0cm}|
|
|
|
|
.. c:type:: v4l2_frequency_band
|
|
|
|
.. flat-table:: struct v4l2_frequency_band
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 1 1 2 1 1
|
|
|
|
* - __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
|
|
- ``index``
|
|
- Identifies the frequency band, set by the application.
|
|
* - __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.
|
|
* - __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.
|
|
* - __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.
|
|
* - __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.
|
|
* - __u32
|
|
- ``reserved``\ [9]
|
|
- Reserved for future extensions.
|
|
|
|
Applications and drivers must set the array to zero.
|
|
|
|
|
|
|
|
.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. _band-modulation:
|
|
|
|
.. flat-table:: Band Modulation Systems
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``V4L2_BAND_MODULATION_VSB``
|
|
- 0x02
|
|
- Vestigial Sideband modulation, used for analog TV.
|
|
* - ``V4L2_BAND_MODULATION_FM``
|
|
- 0x04
|
|
- Frequency Modulation, commonly used for analog radio.
|
|
* - ``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.
|