Messages in this thread | | | From | Stephen Warren <> | Date | Fri, 5 Aug 2011 08:29:38 -0700 | Subject | RE: [PATCH 1/3] irq: If an IRQ is a GPIO, request and configure it |
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Mark Brown wrote at Thursday, August 04, 2011 11:35 PM: > On Thu, Aug 04, 2011 at 08:53:34PM -0700, Stephen Warren wrote: > > > Well, things break. This is essentially the problem I was describing in > > the PATCH 0 email, just with a slightly different motivation. > > There's a bunch of existing code using that idiom.
Certainly.
> > 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? > > But it's not a bug to use a GPIO as an IRQ source, otherwise we wouldn't > have gpio_to_irq() in the first place.
True, but I think there are two cases:
1) Some code legitimately uses a pin as both a GPIO and IRQ, and is fully cognizant of the fact, just like in your example -> no bug.
2) Two pieces of unrelated code somehow accidentally get a GPIO and IRQ number that map to the same resource, e.g. due to incorrect board files or Device Tree content. This is probably a bug, but ends up looking exactly the same as far as the IRQ code's gpio_request call failing in the patch I posted.
> Feels like we need a backchannel > between gpiolib and the IRQ code to do this. Or perhaps the drivers > that implement this should be taking care of setting up the GPIO mode?
-- nvpublic
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