Documentation/media/uapi/v4l/dev-radio.rst - linux - Git at Google

 .. Permission is granted to copy, distribute and/or modify this
 .. document under the terms of the GNU Free Documentation License,
 .. Version 1.1 or any later version published by the Free Software
 .. Foundation, with no Invariant Sections, no Front-Cover Texts
 .. and no Back-Cover Texts. A copy of the license is included at
 .. Documentation/media/uapi/fdl-appendix.rst.
 ..
 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

 .. _radio:

 ***************
 Radio Interface
 ***************

 This interface is intended for AM and FM (analog) radio receivers and
 transmitters.

 Conventionally V4L2 radio devices are accessed through character device
 special files named ``/dev/radio`` and ``/dev/radio0`` to
 ``/dev/radio63`` with major number 81 and minor numbers 64 to 127.


 Querying Capabilities
 =====================

 Devices supporting the radio interface set the ``V4L2_CAP_RADIO`` and
 ``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` flag in the
 ``capabilities`` field of struct
 :c:type:`v4l2_capability` returned by the
 :ref:`VIDIOC_QUERYCAP` ioctl. Other combinations of
 capability flags are reserved for future extensions.


 Supplemental Functions
 ======================

 Radio devices can support :ref:`controls <control>`, and must support
 the :ref:`tuner or modulator <tuner>` ioctls.

 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.


 Programming
 ===========

 Radio devices may have a couple audio controls (as discussed in
 :ref:`control`) such as a volume control, possibly custom controls.
 Further all radio devices have one tuner or modulator (these are
 discussed in :ref:`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
 :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` or
 :ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl reports the
 supported frequency range.
	.. Permission is granted to copy, distribute and/or modify this
	.. document under the terms of the GNU Free Documentation License,
	.. Version 1.1 or any later version published by the Free Software
	.. Foundation, with no Invariant Sections, no Front-Cover Texts
	.. and no Back-Cover Texts. A copy of the license is included at
	.. Documentation/media/uapi/fdl-appendix.rst.
	..
	.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

	.. _radio:

	***************
	Radio Interface
	***************

	This interface is intended for AM and FM (analog) radio receivers and
	transmitters.

	Conventionally V4L2 radio devices are accessed through character device
	special files named ``/dev/radio`` and ``/dev/radio0`` to
	``/dev/radio63`` with major number 81 and minor numbers 64 to 127.


	Querying Capabilities
	=====================

	Devices supporting the radio interface set the ``V4L2_CAP_RADIO`` and
	``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` flag in the
	``capabilities`` field of struct
	:c:type:`v4l2_capability` returned by the
	:ref:`VIDIOC_QUERYCAP` ioctl. Other combinations of
	capability flags are reserved for future extensions.


	Supplemental Functions
	======================

	Radio devices can support :ref:`controls <control>`, and must support
	the :ref:`tuner or modulator <tuner>` ioctls.

	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.


	Programming
	===========

	Radio devices may have a couple audio controls (as discussed in
	:ref:`control`) such as a volume control, possibly custom controls.
	Further all radio devices have one tuner or modulator (these are
	discussed in :ref:`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
	:ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` or
	:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl reports the
	supported frequency range.