64e4954619
The conversion script added some comments at the end. They point to the original DocBook files, with will be removed after the manual fixes. So, they'll be pointing to nowere. So, remove those comments. They'll be forever stored at the Kernel tree. So, if someone wants the references, it is just a matter of looking at the backlog. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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53 lines
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.. -*- coding: utf-8; mode: rst -*-
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.. _radio:
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***************
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Radio Interface
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***************
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This interface is intended for AM and FM (analog) radio receivers and
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transmitters.
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Conventionally V4L2 radio devices are accessed through character device
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special files named ``/dev/radio`` and ``/dev/radio0`` to
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``/dev/radio63`` with major number 81 and minor numbers 64 to 127.
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Querying Capabilities
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=====================
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Devices supporting the radio interface set the ``V4L2_CAP_RADIO`` and
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``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` flag in the
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``capabilities`` field of struct
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:ref:`v4l2_capability <v4l2-capability>` returned by the
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:ref:`VIDIOC_QUERYCAP` ioctl. Other combinations of
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capability flags are reserved for future extensions.
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Supplemental Functions
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======================
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Radio devices can support :ref:`controls <control>`, and must support
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the :ref:`tuner or modulator <tuner>` ioctls.
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They do not support the video input or output, audio input or output,
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video standard, cropping and scaling, compression and streaming
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parameter, or overlay ioctls. All other ioctls and I/O methods are
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reserved for future extensions.
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Programming
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===========
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Radio devices may have a couple audio controls (as discussed in
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:ref:`control`) such as a volume control, possibly custom controls.
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Further all radio devices have one tuner or modulator (these are
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discussed in :ref:`tuner`) with index number zero to select the radio
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frequency and to determine if a monaural or FM stereo program is
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received/emitted. Drivers switch automatically between AM and FM
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depending on the selected frequency. The
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:ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` or
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:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl reports the
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supported frequency range.
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