A better way to sequence driver initialization?

[Paul Mundt]

On Sat, Apr 10, 2010 at 08:33:53PM -0500, Bill Gatliff wrote:
> Grant Likely wrote:
> > On Sat, Apr 10, 2010 at 5:39 PM, Paul Mundt <lethal at linux-sh.org> wrote:
> >   
> >> In cases where you can specifically note that dependencies, doing so will
> >> save you a world of pain. Despite that, it's simply not possible to do
> >> this as a free-for-all. Devices or busses that can tolerate multi-threaded
> >> probing need to be converted over one at a time, but even then you still
> >> need the dependency tracking for those that depend on link order today.
> >>     
> 
> Who's to say a function like gpio_request_wait_for_it(GPIO_NUMBER,
> "dependent-driver") isn't the way to do the dependency tracking?  I
> can't even implement that without a context that can sleep...
> 
In some cases that might be valid, but there are many cases where drivers
can reconfigure their capability sets based on which GPIOs are and aren't
available. Just because a pin isn't available doesn't make it a
show-stopper for the probe path..