I am interested in writing a driver for the I2S interface but unfortunately even the full datasheet that is circulating on the internet is a bit light on the details on how the "MBOX" DMA subsystem should be set up. Unfortunately DMA looks like the only way to actually do any I2S transfers.

Does anyone has access to the AR9331 SDK or any example code from Atheros? Of course I can sign an NDA if this is what it takes.

There's a source code taken out from SDK, however it only can be used as a reference for Your own driver writing, because the driver is not ALSA compatible.

I am thinking of two things I would like to do with this and for the first "experiment" I don't need ALSA. But I am pretty sure I can also handle rewriting it for the ALSA framework. I am only started doing kernel development recently but I have plenty of both embedded and Linux/OS X user-space programming experience.

Would it be possible for me to get said source code fragments from you?

Thank you very much.

Socrates: I went through the code today and unfortunately it looks like it was made for other Atheros chips (the Virian board with the AR7241 processor and the Wasp board with the ar934x SoC). It should be possible to reverse engineer the missing parts using the datasheet but it's a pity this won't work as is.

I found some additional files in the Fritzbox GPL source releases:
http://gpl.back2roots.org/source/fritzb ... ps/ar7240/
http://gpl.back2roots.org/source/fritzb ... ch-ar7240/

They have header files (and even some function implementations) for the AR933x SoC.

I believe the peripheral is almost the same. It should be possible to write a driver using those files as reference.