Re: best way to handle LEDs

[Rich Walker]

Russell King <rmk+lkml@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxx
technical director     251 Liverpool Road   |
need a Hand?           London  N1 1LX       | +UK 20 7700 2487
www.shadow.org.uk/products/newhand.shtml

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/