Re: [alsa-devel] Is the mixer interface in the kernel protect against concurrent access?

On Mon, 2007-12-17 at 16:43 +0100, Jaroslav Kysela wrote:

On Mon, 17 Dec 2007, Hans-Christian Egtvedt wrote:

...

I am solving a locking bug in the at73c213 SPI sound driver, and wondered if the mixer API is protected against concurrent access in ALSA? Or should I implement a mutex to protect my hardware against concurrent access?

Control r/w callbacks are protected with a semaphore - card->controls_rwsem . See sound/core/control.c for more details. Anyway, you need to protect your registers with spinlocks (if required of course).

Thanks for the feedback. I settled upon a mutex since the SPI driver can not use spinlocks due to a might sleepy spi_sync function call.