mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-27 04:54:41 +08:00
8e080c2e6c
The V4L and DVB API's are there for a long time. however, up to now, no efforts were done to merge them to kernel DocBook. This patch adds the current versions of the specs as an unique compendium. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
58 lines
2.0 KiB
XML
58 lines
2.0 KiB
XML
<title>Radio Interface</title>
|
|
|
|
<para>This interface is intended for AM and FM (analog) radio
|
|
receivers and transmitters.</para>
|
|
|
|
<para>Conventionally V4L2 radio devices are accessed through
|
|
character device special files named <filename>/dev/radio</filename>
|
|
and <filename>/dev/radio0</filename> to
|
|
<filename>/dev/radio63</filename> with major number 81 and minor
|
|
numbers 64 to 127.</para>
|
|
|
|
<section>
|
|
<title>Querying Capabilities</title>
|
|
|
|
<para>Devices supporting the radio interface set the
|
|
<constant>V4L2_CAP_RADIO</constant> and
|
|
<constant>V4L2_CAP_TUNER</constant> or
|
|
<constant>V4L2_CAP_MODULATOR</constant> flag in the
|
|
<structfield>capabilities</structfield> field of &v4l2-capability;
|
|
returned by the &VIDIOC-QUERYCAP; ioctl. Other combinations of
|
|
capability flags are reserved for future extensions.</para>
|
|
</section>
|
|
|
|
<section>
|
|
<title>Supplemental Functions</title>
|
|
|
|
<para>Radio devices can support <link
|
|
linkend="control">controls</link>, and must support the <link
|
|
linkend="tuner">tuner or modulator</link> ioctls.</para>
|
|
|
|
<para>They do not support the video input or output, audio input
|
|
or output, video standard, cropping and scaling, compression and
|
|
streaming parameter, or overlay ioctls. All other ioctls and I/O
|
|
methods are reserved for future extensions.</para>
|
|
</section>
|
|
|
|
<section>
|
|
<title>Programming</title>
|
|
|
|
<para>Radio devices may have a couple audio controls (as discussed
|
|
in <xref linkend="control" />) such as a volume control, possibly custom
|
|
controls. Further all radio devices have one tuner or modulator (these are
|
|
discussed in <xref linkend="tuner" />) with index number zero to select
|
|
the radio frequency and to determine if a monaural or FM stereo
|
|
program is received/emitted. Drivers switch automatically between AM and FM
|
|
depending on the selected frequency. The &VIDIOC-G-TUNER; or
|
|
&VIDIOC-G-MODULATOR; ioctl
|
|
reports the supported frequency range.</para>
|
|
</section>
|
|
|
|
<!--
|
|
Local Variables:
|
|
mode: sgml
|
|
sgml-parent-document: "v4l2.sgml"
|
|
indent-tabs-mode: nil
|
|
End:
|
|
-->
|