RE: [PATCH 1/3] irq: If an IRQ is a GPIO, request and configure it

[Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

Mark Brown wrote at Thursday, August 04, 2011 6:02 PM:
> On Thu, Aug 04, 2011 at 05:00:18PM -0600, Stephen Warren wrote:
> 
> > +	} else {
> > +		gpio = irq_to_gpio(irq);
> > +		if (gpio_is_valid(gpio)) {
> > +			ret = gpio_request(gpio, new->name);
> > +			if (ret < 0)
> > +				goto out_mask;
> > +			ret = gpio_direction_input(gpio);
> > +			if (ret < 0)
> > +				goto out_mask;
> > +		}
> 
> If you treat failures as an error what happens when a driver is using a
> GPIO as both an interrupt and a GPIO?  For example a driver which
> monitors the level on a GPIO and uses edge triggered IRQs to be notified
> of state changes.

Well, things break. This is essentially the problem I was describing in
the PATCH 0 email, just with a slightly different motivation.

I suppose that an alternative here would be to simply ignore any errors
from gpio_request. This might have the benefit of removing the need for
the other two patches I posted in the series. However, it seems a little
dirty; one benefit of the IRQ code calling gpio_request and honoring
errors would be to detect when some completely unrelated code had a bug
and had called gpio_request on the GPIO before. Such detection would be
non-existent if we don't error out on gpio_request. Perhaps some mechanism
is needed to indicate that the driver has explicitly already called
gpio_request for a legitimate shared purpose, and only then ignore
errors?

--
nvpublic