Documentation/admin-guide/media/si4713.rst

Source file repositories/reference/linux-study-clean/Documentation/admin-guide/media/si4713.rst

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Documentation/admin-guide/media/si4713.rst
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GPL-2.0

.. include:: <isonum.txt>

The Silicon Labs Si4713 FM Radio Transmitter Driver
===================================================

Copyright |copy| 2009 Nokia Corporation

Contact: Eduardo Valentin <eduardo.valentin@nokia.com>


Information about the Device
----------------------------

This chip is a Silicon Labs product. It is an I2C device, currently on 0x63 address.
Basically, it has transmission and signal noise level measurement features.

The Si4713 integrates transmit functions for FM broadcast stereo transmission.
The chip also allows integrated receive power scanning to identify low signal
power FM channels.

The chip is programmed using commands and responses. There are also several
properties which can change the behavior of this chip.

Users must comply with local regulations on radio frequency (RF) transmission.

Device driver description
-------------------------

There are two modules to handle this device. One is an I2C device driver
and the other is a platform driver.

The I2C device driver exports a v4l2-subdev interface to the kernel.
All properties can also be accessed by v4l2 extended controls interface, by
using the v4l2-subdev calls (g_ext_ctrls, s_ext_ctrls).

The platform device driver exports a v4l2 radio device interface to user land.
So, it uses the I2C device driver as a sub device in order to send the user
commands to the actual device. Basically it is a wrapper to the I2C device driver.

Applications can use v4l2 radio API to specify frequency of operation, mute state,
etc. But mostly of its properties will be present in the extended controls.

When the v4l2 mute property is set to 1 (true), the driver will turn the chip off.

Properties description
----------------------

The properties can be accessed using v4l2 extended controls.
Here is an output from v4l2-ctl util:

.. code-block:: none

	/ # v4l2-ctl -d /dev/radio0 --all -L
	Driver Info:
		Driver name   : radio-si4713
		Card type     : Silicon Labs Si4713 Modulator
		Bus info      :
		Driver version: 0
		Capabilities  : 0x00080800
			RDS Output
			Modulator
	Audio output: 0 (FM Modulator Audio Out)
	Frequency: 1408000 (88.000000 MHz)
	Video Standard = 0x00000000
	Modulator:
		Name                 : FM Modulator
		Capabilities         : 62.5 Hz stereo rds
		Frequency range      : 76.0 MHz - 108.0 MHz

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