On 09/02/2013 03:25 AM, Lars Poeschel wrote: > Am Freitag, 30. August 2013, 13:55:26 schrieb Stephen Warren: >> On 08/29/2013 06:24 PM, Javier Martinez Canillas wrote: >> ... >> >>> We have been trying to solve this issue for a few months by now and Linus' >>> approach seems to be the most sensible solution to me. >>> >>> Drivers that request an IRQ and assume that platform code will request and >>> setup the GPIO have been broken since the boards using these drivers were >>> migrated to DT (e.g: smsc911x on OMAP2+ boards). >> >> That's only true if the driver for the GPIO controller is buggy. >> Whatever request_irq() maps down to in the GPIO/IRQ controller driver >> simply needs to set up the pin as an interrupt input, then it doesn't >> matter which order the driver does things. > > Is it really that easy? Yes. > request_irq() should request the gpio and set it to input that it needs to > fulfill the irq request. That would then be the way to go for new drivers and > in the DT case. Either explicitly request the GPIO, or simply directly program the HW in whatever way is required for the pin to operate as an IRQ. > Some leagcy drivers currently do this: > > request_gpio(gpio); > gpio_direction_input(gpio); > request_irq(gpio_to_irq(gpio)); > > In that case request_irq should not fail because the driver is already the > correct owner of this gpio. But if some other entity owns this gpio it should > fail. Yes. > Also if I understand you correct the other way round should also possible: > > request_irq(gpio_to_irq(gpio)); > request_gpio(gpio); > gpio_direction_input(gpio); > > request_irq() also requests the gpio then but the following request_gpio() > should also not fail. I don't believe that code sequence is currently banned. If we want to ban it, we should document that. Until this is documented as being banned, I think we must fully support that code sequence. > To have it work that way we have to track the owners of all requested gpios > somewhere. Or am I wrong here? > Where and how to record these owners? Can gpio system achieve this? gpios are > requested without an owning device. Yes. But, I believe we need to fully track every GPIO/IRQ owner already right now; if a driver (not the GPIO/IRQ chip driver, but a driver that uses the GPIOs/IRQs) calls gpio_request()/request_irq(), and this patch has already requested them, then we already need to fully track GPIO/IRQ ownership to make sure that the driver's own requests aren't failed because the DT/GPIO core has already requested them on its behalf. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
