1 .. SPDX-License-Identifier: GFDL-1.1-no-invari
2
3 .. _radio:
4
5 ***************
6 Radio Interface
7 ***************
8
9 This interface is intended for AM and FM (anal
10 transmitters.
11
12 Conventionally V4L2 radio devices are accessed
13 special files named ``/dev/radio`` and ``/dev/
14 ``/dev/radio63`` with major number 81 and mino
15
16
17 Querying Capabilities
18 =====================
19
20 Devices supporting the radio interface set the
21 ``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` f
22 ``capabilities`` field of struct
23 :c:type:`v4l2_capability` returned by the
24 :ref:`VIDIOC_QUERYCAP` ioctl. Other combinatio
25 capability flags are reserved for future exten
26
27
28 Supplemental Functions
29 ======================
30
31 Radio devices can support :ref:`controls <cont
32 the :ref:`tuner or modulator <tuner>` ioctls.
33
34 They do not support the video input or output,
35 video standard, cropping and scaling, compress
36 parameter, or overlay ioctls. All other ioctls
37 reserved for future extensions.
38
39
40 Programming
41 ===========
42
43 Radio devices may have a couple audio controls
44 :ref:`control`) such as a volume control, poss
45 Further all radio devices have one tuner or mo
46 discussed in :ref:`tuner`) with index number z
47 frequency and to determine if a monaural or FM
48 received/emitted. Drivers switch automatically
49 depending on the selected frequency. The
50 :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` or
51 :ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>`
52 supported frequency range.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.