Re: best way to handle LEDs

[Vojtech Pavlik <vojtech@suse.cz>]

On Thu, Nov 03, 2005 at 02:49:04PM +0000, Russell King wrote:
> On Thu, Nov 03, 2005 at 10:57:26AM +0100, Pavel Machek wrote:
> > Hi!
> > 
> > > > Except the led code that is being proposed CAN sit on top of a generic
> > > > GPIO layer.
> > > 
> > > 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.
> > 
> > Can't you just busywait? Yes, it is ugly in general, but perhaps it
> > is better than alternatives...
> 
> Does the i2c layer support busy waiting or are you suggesting something
> else?

It usually doesn't support anything else. At least on the controllers
I've seen the drivers for.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR