accelerometer driver

[Andy Green]

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Somebody in the thread at some point said:
| It seems like the accelerometers have the following:
|
| sensitive to losing an edge trigger

We just suspect it, nobody showed it yet... it would probably be a bug
in the driver handling or s3c stuff rather than accelerometer "feature".

| occur at a periodic rate
| access conflicts with other drivers so should be done outside of irq

I have a nice patch coming that just does it bitbang the whole way using
IRQs off as locking throughout.

| Does it make sense to just turn off the irq and have the driver use a
| delayed work queue to poll at a given rate?

Interrupts are at least somewhat synchronized to the source, I think it
will suffer from dropped samples otherwise.  But, at some point we have
to take more radical measures if we don't solve it...

- -Andy
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