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diff --git a/Documentation/DocBook/media/v4l/dev-radio.xml b/Documentation/DocBook/media/v4l/dev-radio.xml new file mode 100644 index 00000000000..73aa90b45b3 --- /dev/null +++ b/Documentation/DocBook/media/v4l/dev-radio.xml @@ -0,0 +1,57 @@ + <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: + --> |