On Fri, Aug 05, 2011 at 10:40:17AM +0100, Russell King - ARM Linux wrote: > On Thu, Aug 04, 2011 at 05:00:17PM -0600, Stephen Warren wrote: > > In http://www.spinics.net/lists/linux-tegra/msg01731.html, Mark Brown > > pointed out that it was a little silly forcing every board or driver > > to gpio_request() a GPIO that is later converted to an IRQ, and passed > > to request_irq. The first patch in this series instead makes the core > > IRQ code perform these calls when appropriate, to avoid duplicating it > > everywhere. > > Trying to go from IRQ to GPIO is not a good idea - most of the > IRQ <-> GPIO macros we have today are just plain broken. Many of them > just add or subtract a constant, which means non-GPIO IRQs have an > apparant GPIO number too. Couple this with the fact that all positive > GPIO numbers are valid, and this is a recipe for wrong GPIOs getting > used and GPIOs being requested for non-GPIO IRQs. Yes, and there's a pile without these defined/ > I think this was also discussed in the past, and the conclusion was that > IRQs should be kept separate from GPIOs. Maybe views have changed since > then... > > However, if we do want to do this, then it would be much better to provide > a new API for requesting GPIO IRQs, eg: > > gpio_request_irq() > > which would wrap around request_threaded_irq(), takes a GPIO number, > does the GPIO->IRQ conversion internally, and whatever GPIO setup is > required. Something like this: > > int gpio_request_threaded_irq(int gpio, irq_handler_t handler, > irq_handler_t thread_fn, unsigned long flags, const char *name, > void *dev) > { > int ret; > > if (!gpio_valid(gpio)) > return -EINVAL; > > ret = gpio_request_one(gpio, GPIOF_IN, name); > if (ret) > return ret; > > ret = request_threaded_irq(gpio_to_irq(gpio), handler, thread_fn, > flags, name, dev); > if (ret) > gpio_free(gpio); > > return ret; > } > > This then limits the exposure of the GPIO<->IRQ conversion macros to just > GPIOs, where the buggy nature of the existing conversions won't impact on > non-GPIO IRQs. What about the case where we need to turn GPIO numbers into interrupts to pass to other drivers? In the case where we have a gpio chip that is providing interrupt services to other drivers (such as serial chip). Having looked at a couple of IIO drivers, it seems that the need to use irq_to_gpio() seems to be to check if the device needs to be service. It would be useful to see if this is due to a problem with the threadder IRQ handler (and if so, may need fixing for the general case). -- Ben Dooks, ben@xxxxxxxxx, http://www.fluff.org/ben/ Large Hadron Colada: A large Pina Colada that makes the universe disappear. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
