Adding kqueue to /dev/dsp

Hello,

I already talked to christos@ and he's OK with me adding the support for 
kqueue to /dev/dsp, but I never saw any docs on how to implement it in 
the kernel. Could somebody advise on how to add kqueue support to 
existing device? I mean, if you could point out the simple device code 
with kqueue support, I would be glad to follow the logic there and 
learn, for start. Thank you!

Regards,
meka