Hi Ricard,
On 11/11/15 12:59, Ricard Wanderlof wrote:
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.
Well, this is not ALSA specific, it really depends on which framework your driver is based on, but they all share similar flow on probe and remove driver.
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.
What exactly do you want? If it is driver that register and unregister cards based on the user interaction of probing and removing that module from user-space, then you are not looking for a driver. What you are looking for is just a kernel module. The only way of interacting with it is dealing with module_init and module_exit.
On the other hand, if in fact you want a driver, then check sound/drivers/dummy.c for an example. You can also read the Documentation/driver-model/platform.txt for more info.