On Fri, Aug 05, 2011 at 08:43:20AM -0700, Stephen Warren wrote: > Russell King - ARM Linux wrote at Friday, August 05, 2011 3:40 AM: > > 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. > > > > 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: > > With that approach, drivers need to explicitly know whether they're > passed a GPIO or an IRQ, and do something different, or they need to > choose to only accept a GPIO or IRQ. You completely missed the biggest reason why your approach is broken. + gpio = irq_to_gpio(irq); + if (gpio_is_valid(gpio)) Let's look at the code: #define ARCH_NR_GPIOS 256 static inline bool gpio_is_valid(int number) { return number >= 0 && number < ARCH_NR_GPIOS; } Now, let's take AT91: #define irq_to_gpio(irq) (irq) This doesn't define ARCH_NR_GPIOS, so it gets the default 256. Now lets take a random selection of the AT91 interrupt numbers: #define AT91RM9200_ID_US3 9 /* USART 3 */ #define AT91RM9200_ID_MCI 10 /* Multimedia Card Interface */ #define AT91RM9200_ID_UDP 11 /* USB Device Port */ #define AT91RM9200_ID_TWI 12 /* Two-Wire Interface */ #define AT91RM9200_ID_SPI 13 /* Serial Peripheral Interface */ #define AT91RM9200_ID_SSC0 14 /* Serial Synchronous Controller 0 */ #define AT91RM9200_ID_SSC1 15 /* Serial Synchronous Controller 1 */ None of these are GPIOs. Yet gpio_is_valid(irq_to_gpio(AT91RM9200_ID_TWI)) is true. That's the problem - it's undefined whether gpio_is_valid(irq_to_gpio(irq)) returns true or false for any particular interrupt. There's no multiplexing through gpiolib for the IRQ-to-GPIO mapping either, so it doesn't work for off-SoC GPIOs. So, you can't reliably go from interrupt numbers to GPIO numbers - it's just not supported. So to throw this into the IRQ layer is just going to end up breaking a hell of a lot of platforms. Now, stack on top of that a discussion at the Linaro Connect conference this week where we discussed getting rid of IRQ numbers entirely, and our desire to kill off irq_to_gpio() and I think it makes this approach a non-starter. > So it seems like, as was mentioned elsewhere in this thread, the upshot of > this conversation is that interrupt chip drivers should do this internally, > both to avoid requiring a general irq_to_gpio function, and because calling > gpio_direction_input for GPIOs-used-as-IRQs isn't appropriate for all > hardware. That would be more appropriate, because the IRQ chip stuff at least knows if there's a GPIO associated with it. There's still the unanswered question whether we even want the IRQ layer to do this kind of stuff, and the previous decision on that I believe was in the negative. So I think Thomas needs to respond to that point first. -- 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
