[Gta04-owner] fm-tuner

[Andreas Kemnade]

On Thu, 24 Oct 2013 10:02:23 +0200
"Dr. H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> 
[...]
> 
> There is no platform data (yet) for our "si47xx_codec_audio", because we have no I2C control
> through the kernel driver. Usually it would be provided by such a struct si47xx_setup_data.
> 
> It is intended to add some amixer controls for this "sound card" to control the frequency and
> some other parameters.
> 
> Currently we leave all i2c control to user-space.
> 
> The reason is that the Linux kernel usually treats fm-radios completely different and not as
> a sound card... There are drivers for I2C-Si4721 but AFAIK they assume an analog signal
> path.
> 
> But then I don't know how to write such a driver but still using the McBSP interface because
> it must be enabled/disabled in sync with the Si4721.
> 
I have now looked more closely into various v4l devices. The common
structure I see is always:
video and control through v4l including some glue. Audio via an usual
soundcard interface, usually even through standard drivers. My usb
video capture thingy uses the standard usb audio driver.
Some years ago I came across a silabs FM usb stick. The standard usb
audio driver could be used. I wrote a simple driver using libusb for
setting the frequency. 

I would propose to write the sample rate via i2c in the corresponding
dai codec interface and register a v4l interface for the other stuff.

Greetings
Andreas Kemnade
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