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1 | .. -*- coding: utf-8; mode: rst -*- |
2 | ||
3 | .. _radio: | |
4 | ||
5 | *************** | |
6 | Radio Interface | |
7 | *************** | |
8 | ||
9 | This interface is intended for AM and FM (analog) radio receivers and | |
10 | transmitters. | |
11 | ||
12 | Conventionally V4L2 radio devices are accessed through character device | |
13 | special files named ``/dev/radio`` and ``/dev/radio0`` to | |
14 | ``/dev/radio63`` with major number 81 and minor numbers 64 to 127. | |
15 | ||
16 | ||
17 | Querying Capabilities | |
18 | ===================== | |
19 | ||
20 | Devices supporting the radio interface set the ``V4L2_CAP_RADIO`` and | |
21 | ``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` flag in the | |
22 | ``capabilities`` field of struct | |
23 | :ref:`v4l2_capability <v4l2-capability>` returned by the | |
7347081e | 24 | :ref:`VIDIOC_QUERYCAP` ioctl. Other combinations of |
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25 | capability flags are reserved for future extensions. |
26 | ||
27 | ||
28 | Supplemental Functions | |
29 | ====================== | |
30 | ||
31 | Radio devices can support :ref:`controls <control>`, and must support | |
32 | the :ref:`tuner or modulator <tuner>` ioctls. | |
33 | ||
34 | They do not support the video input or output, audio input or output, | |
35 | video standard, cropping and scaling, compression and streaming | |
36 | parameter, or overlay ioctls. All other ioctls and I/O methods are | |
37 | reserved for future extensions. | |
38 | ||
39 | ||
40 | Programming | |
41 | =========== | |
42 | ||
43 | Radio devices may have a couple audio controls (as discussed in | |
44 | :ref:`control`) such as a volume control, possibly custom controls. | |
45 | Further all radio devices have one tuner or modulator (these are | |
46 | discussed in :ref:`tuner`) with index number zero to select the radio | |
47 | frequency and to determine if a monaural or FM stereo program is | |
48 | received/emitted. Drivers switch automatically between AM and FM | |
49 | depending on the selected frequency. The | |
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50 | :ref:`VIDIOC_G_TUNER` or |
51 | :ref:`VIDIOC_G_MODULATOR` ioctl reports the | |
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52 | supported frequency range. |
53 | ||
54 | ||
55 | .. ------------------------------------------------------------------------------ | |
56 | .. This file was automatically converted from DocBook-XML with the dbxml | |
57 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes | |
58 | .. from the linux kernel, refer to: | |
59 | .. | |
60 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook | |
61 | .. ------------------------------------------------------------------------------ |