[Gta04-owner] first tries with si4721

Dr. H. Nikolaus Schaller hns at goldelico.com
Fri Feb 10 09:10:05 CET 2012

Am 09.02.2012 um 22:30 schrieb Andreas Kemnade:

> Hi,
> I played a bit with the si4721 from userspace using /dev/i2c-2. According
> to SNR/RSSI values it seems to find something.
> Now I am wondering how I can hear that.
> In 2.6.32 arecord -l does not list a gta04fm pcm
> aplay -l does
> What needs to be done there? That's not a part of the kernel
> I know well. Is the clock really from the si4721? 

Well, the ALSA driver is just a stub that compiles and presents
some more or less useful interface.

The driver for the PCM interface to the Si47xx is here


And the ALSA driver here:


They do not initialize much more than the McBSP link.
And they do not define amixer capabilities like recording or play back volume etc.

> I understand the datasheet so that the clock comes from host.

If I remember correctly, this is a parameter of the McBSP interface
and can be defined in the gta04-fm.c source where the setup of
the DAI link is done.

Generally, it is not clear to me if the Si47xx driver shall be an ALSA
device and e.g. the frequency tuning should be done through an amixer

Or if it should be a V4L device (without video). I think the existing
drivers take this approach.

Any of both approaches may be the right path but IMHO they are
very incompatible and can not be operated in parallel. I.e. we, the
kernel developers, have to decide.


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