I don't know how to do an async i2c driver.
Queue transfer descriptors in a linked list and have the i2c interrupt service them, in queue order, calling a callback when each is completed. Yes, it must be interrupt based.
I guess it's just the codec i2c driver on AMS that is like that. On i.MX31 it's the serial driver.
IMO, the simplest is to
do not too much in the interrupt itself. Hence the interrupt in my proposal just wakes up a thread that does the actual work.
It's not the cheapest if the other way is possible. Threads have a pretty large structure and the required stack to go with it.
On the AMS targets, i2c to the fm tuner is done by "bit-banging" (GPIO toggling) using udelays to do the timing. Can you do async with that?
Forgot about that. A pity but no, that's out of the question.
The idea is that the fm tuner driver knows when a channel is switched, tuner is powered off or on, etc. You can't just re-read it, because we want fresh data from the current station.
I think that's basically what I meant-- clear it when someone messes with the tuner in certain ways but push that up to any UI so it can keep in sync.
Mike
