V4L/DVB (9482): Documentation, especially regarding audio and informational links

This patch adds a recommendation to select SND_USB_AUDIO for listing and
adds a documentation file for si470x.

Signed-off-by: Tobias Lorenz <tobias.lorenz@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/si470x.txt

@@ -0,0 +1,118 @@
+Driver for USB radios for the Silicon Labs Si470x FM Radio Receivers
+
+Copyright (c) 2008 Tobias Lorenz <tobias.lorenz@gmx.net>
+
+
+Information from Silicon Labs
+=============================
+Silicon Laboratories is the manufacturer of the radio ICs, that nowadays are the
+most often used radio receivers in cell phones. Usually they are connected with
+I2C. But SiLabs also provides a reference design, which integrates this IC,
+together with a small microcontroller C8051F321, to form a USB radio.
+Part of this reference design is also a radio application in binary and source
+code. The software also contains an automatic firmware upgrade to the most
+current version. Information on these can be downloaded here:
+http://www.silabs.com/usbradio
+
+
+Supported ICs
+=============
+The following ICs have a very similar register set, so that they are or will be
+supported somewhen by the driver:
+- Si4700: FM radio receiver
+- Si4701: FM radio receiver, RDS Support
+- Si4702: FM radio receiver
+- Si4703: FM radio receiver, RDS Support
+- Si4704: FM radio receiver, no external antenna required
+- Si4705: FM radio receiver, no external antenna required, RDS support, Dig I/O
+- Si4706: Enhanced FM RDS/TMC radio receiver, no external antenna required, RDS
+	  Support
+- Si4707: Dedicated weather band radio receiver with SAME decoder, RDS Support
+- Si4708: Smallest FM receivers
+- Si4709: Smallest FM receivers, RDS Support
+More information on these can be downloaded here:
+http://www.silabs.com/products/mcu/Pages/USBFMRadioRD.aspx
+
+
+Supported USB devices
+=====================
+Currently the following USB radios (vendor:product) with the Silicon Labs si470x
+chips are known to work:
+- 10c4:818a: Silicon Labs USB FM Radio Reference Design
+- 06e1:a155: ADS/Tech FM Radio Receiver (formerly Instant FM Music) (RDX-155-EF)
+- 1b80:d700: KWorld USB FM Radio SnapMusic Mobile 700 (FM700)
+
+
+Software
+========
+Testing is usually done with most application under Debian/testing:
+- fmtools - Utility for managing FM tuner cards
+- gnomeradio - FM-radio tuner for the GNOME desktop
+- gradio - GTK FM radio tuner
+- kradio - Comfortable Radio Application for KDE
+- radio - ncurses-based radio application
+
+There is also a library libv4l, which can be used. It's going to have a function
+for frequency seeking, either by using hardware functionality as in radio-si470x
+or by implementing a function as we currently have in every of the mentioned
+programs. Somewhen the radio programs should make use of libv4l.
+
+For processing RDS information, there is a project ongoing at:
+http://rdsd.berlios.de/
+
+There is currently no project for making TMC sentences human readable.
+
+
+Audio Listing
+=============
+USB Audio is provided by the ALSA snd_usb_audio module. It is recommended to
+also select SND_USB_AUDIO, as this is required to get sound from the radio. For
+listing you have to redirect the sound, for example using one of the following
+commands.
+
+If you just want to test audio (very poor quality):
+cat /dev/dsp1 > /dev/dsp
+
+If you use OSS try:
+sox -2 --endian little -r 96000 -t oss /dev/dsp1 -t oss /dev/dsp
+
+If you use arts try:
+arecord -D hw:1,0 -r96000 -c2 -f S16_LE | artsdsp aplay -B -
+
+
+Module Parameters
+=================
+After loading the module, you still have access to some of them in the sysfs
+mount under /sys/module/radio_si470x/parameters. The contents of read-only files
+(0444) are not updated, even if space, band and de are changed using private
+video controls. The others are runtime changeable.
+
+
+Errors
+======
+Increase tune_timeout, if you often get -EIO errors.
+
+When timed out or band limit is reached, hw_freq_seek returns -EAGAIN.
+
+If you get any errors from snd_usb_audio, please report them to the ALSA people.
+
+
+Open Issues
+===========
+V4L minor device allocation and parameter setting is not perfect. A solution is
+currently under discussion.
+
+There is an USB interface for downloading/uploading new firmware images. Support
+for it can be implemented using the request_firmware interface.
+
+There is a RDS interrupt mode. The driver is already using the same interface
+for polling RDS information, but is currently not using the interrupt mode.
+
+There is a LED interface, which can be used to override the LED control
+programmed in the firmware. This can be made available using the LED support
+functions in the kernel.
+
+
+Other useful information and links
+==================================
+http://www.silabs.com/usbradio

drivers/media/radio/Kconfig

@@ -355,6 +355,20 @@ config USB_SI470X
 	tristate "Silicon Labs Si470x FM Radio Receiver support"
 	depends on USB && VIDEO_V4L2
 	---help---
+	  This is a driver for USB devices with the Silicon Labs SI470x
+	  chip. Currently these devices are known to work:
+	  - 10c4:818a: Silicon Labs USB FM Radio Reference Design
+	  - 06e1:a155: ADS/Tech FM Radio Receiver (formerly Instant FM Music)
+	  - 1b80:d700: KWorld USB FM Radio SnapMusic Mobile 700 (FM700)
+
+	  Sound is provided by the ALSA USB Audio/MIDI driver. Therefore
+	  if you don't want to use the device solely for RDS receiving,
+	  it is recommended to also select SND_USB_AUDIO.
+
+	  Please have a look at the documentation, especially on how
+	  to redirect the audio stream from the radio to your sound device:
+	  Documentation/video4linux/si470x.txt
+
 	  Say Y here if you want to connect this type of radio to your
 	  computer's USB port.
 

drivers/media/radio/radio-si470x.c

@@ -24,19 +24,6 @@
  */
 
 
-/*
- * User Notes:
- * - USB Audio is provided by the alsa snd_usb_audio module.
- *   For listing you have to redirect the sound, for example using:
- *   arecord -D hw:1,0 -r96000 -c2 -f S16_LE | artsdsp aplay -B -
- * - regarding module parameters in /sys/module/radio_si470x/parameters:
- *   the contents of read-only files (0444) are not updated, even if
- *   space, band and de are changed using private video controls
- * - increase tune_timeout, if you often get -EIO errors
- * - hw_freq_seek returns -EAGAIN, when timed out or band limit is reached
- */
-
-
 /*
  * History:
  * 2008-01-12	Tobias Lorenz <tobias.lorenz@gmx.net>