[alsa-devel] Unregister a card from userspace?

[Ricard Wanderlof]

On Wed, 11 Nov 2015, Felipe Ferreri Tonello wrote:

> > But that is precisely the problem. The framework that manages the 
> > insertion and deletion of modules notes that my module has a usage count 
> > that is > 0 (in my case it is 2, which I'm convinced is because the card 
> > has been registered with ALSA), and refuses to free the module. So there 
> > is now way any unregister_card call can be made when my module is freed, 
> > as due to the usage count it would never even be attempted.
> 
> Do you mean that unbind is never called? Well, the framework should call
> bind/unbind for each user of your module.

Ok, I didn't know that. It's the first time I've been writing an ALSA 
driver as a loadable module.

> How is your architecture? If you use one card for each probe of module
> then each bind should create one device, right?

In this case, it is a device which is located on the SoC. There is only 
one instance of it. When the module is loaded, it loads a codec driver 
with its associated DAI driver, a PCM driver, snd-soc-dummy-dai, and then 
a machine driver to tie it all together, finally registering the card with 
ALSA.

Looking in /sys/bus/platform/devices, there seems to be one device created 
for the codec itself, and one for the machine driver. I don't know if 
that's right or wrong, the ALSA driver hierarchy works in the sense that I 
can capture audio from it anyway.

/Ricard
-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30