Re: best way to handle LEDs

Rich Walker
2005-11-03T15:17:01Z

Russell King <rmk+lkml@arm.linux.org.uk> writes:

>
> I also have issues with a generic GPIO layer. As I mentioned in the
> past, there's serious locking issues with any generic abstraction of
> GPIOs.
>
> 1. You want to be able to change GPIO state from interrupts. This
> implies you can not sleep in GPIO state changing functions.
>
> 2. Some GPIOs are implemented on I2C devices. This means that to
> change state, you must sleep.
>
> (1) and (2) are incompatible requirements, so you can not offer a
> generic interface for these GPIOs which has a consistent behaviour -
> where users of the interface know whether the function may sleep or
> may be used from interrupt context.
>

So you have a request_gpio API, where you specify usage characteristics
and get back a handle?

cheers, Rich.

--
rich walker | Shadow Robot Company | rw@shadow.org.uk
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