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).