Hi Linus, Sorry for the late reply. On Thursday 22 August 2013 00:02:39 Linus Walleij wrote: > On Tue, Aug 20, 2013 at 12:04 AM, Laurent Pinchart wrote: > > On Wednesday 31 July 2013 01:44:53 Linus Walleij wrote: > >> I don't see how sharing works here, or how another user, i.e. another one > >> than the user wanting to recieve the IRQ, can validly request such a > >> line? What would the usecase for that valid request be? > > > > When the GPIO is wired to a status signal (such as an MMC card detect > > signal) the driver might want to read the state of the signal > > independently of the interrupt handler. > > That is true. But for such a complex usecase I think it's reasonable that > we only specify the GPIO in the device tree, and the driver utilizing the > IRQ need to take that and perform gpio_to_irq() on it, and then it still > works to use it both ways. I'm pretty sure I would have had an objection a couple of weeks ago when I was looking into this, but I can't think of another use case for now, so I agree with you. > >> Basically I believe these two things need to be exclusive in the DT > >> world: > >> > >> A: request_irq(a resource passed from "interrupts"); > >> -> core implicitly performs gpio_request() > >> gpio_direction_input() > >> > >> B: gpio_request(a resource passed from "gpios"); > >> gpio_direction_input() > >> request_irq(gpio_to_irq()) > >> > >> Never both. And IIUC that was what happened in the OMAP case. > > > > Isn't the core issue that we can translate a GPIO number to an IRQ number, > > but not the other way around ? If that could be done, we could request > > the GPIO and configure it as an input when the IRQ is requested. > > That is true. It would be easier if all GPIO drivers has an irqchip and > and irqdomain, then we could implement irq_to_gpio() properly in gpiolib > and this would not be a problem. Alas, not all do. > > But I also think that the DT contains (as demonstrated by the patch) > all information about what interrupts and GPIOs may conflict, so I > also see this as something of a consistency check, but it could go > in either way. -- Regards, Laurent Pinchart -- 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
