path: root/Documentation/DocBook/media/v4l/dev-radio.xml
diff options
authorFathi Boudra <fathi.boudra@linaro.org>2013-04-28 09:33:08 +0300
committerFathi Boudra <fathi.boudra@linaro.org>2013-04-28 09:33:08 +0300
commit3b4bd47f8f4ed3aaf7c81c9b5d2d37ad79fadf4a (patch)
treeb9996006addfd7ae70a39672b76843b49aebc189 /Documentation/DocBook/media/v4l/dev-radio.xml
Imported Upstream version 3.9.0HEADupstream/3.9.0upstreammaster
Diffstat (limited to 'Documentation/DocBook/media/v4l/dev-radio.xml')
1 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/dev-radio.xml b/Documentation/DocBook/media/v4l/dev-radio.xml
new file mode 100644
index 00000000..3e6ac73b
--- /dev/null
+++ b/Documentation/DocBook/media/v4l/dev-radio.xml
@@ -0,0 +1,49 @@
+ <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
+reports the supported frequency range.</para>
+ </section>