On 09/24/2013 02:26 AM, Linus Walleij wrote: > On Mon, Sep 23, 2013 at 10:12 PM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: >> On 09/23/2013 01:53 PM, Linus Walleij wrote: > >>> I think the kernel should prevent such things. >> >> It might be nice if it could do that. >> >> However, that is 100% unrelated to the problem at hand. > > I don't think it is unrelated when the old OMAP boardfile-based > code definately prevents such uses by its strict usage > of gpio_request() for all IRQ-bound GPIOs. > > I think not preventing it for the DT boot path is setting lower > standards for DT code than for boardfile code which is not > what we should be doing. Semantics matter. In the old board file code, the gpio_request()s were present to work around the bug in the OMAP driver where request_irq() wouldn't configure the IRQ signal correctly. That's the primary reason those calls were there. Now, this had the side-effect of also preventing anything else from calling gpio_request() on those GPIOs, but that wasn't the primary motivation; just a convenient effect. ... > Solving the issue that e.g. two different drivers competing about the > same resource (as in one driver requesting an IRQ and another one > requesting a GPIO) is not what I'm after here. > > I'm more after the GPIO subsystem having knowledge of a certain > GPIO line being requested for IRQ, and denying that line to be set > as input. s/input/output/ I assume. ... > Maybe this can actually be achieved quite easily with > an additional API? Like gpio_lock_as_irq(gpio) which flags this > in .flags of struct gpio_desc and prevent such things? > > Alexandre what do you think about this idea? > >> Equally, I am actually not 100% sure we want the core to prevent this. >> Why shouldn't two different drivers request the same IRQ? Why shouldn't >> at least one driver, perhaps more, request the pin as a GPIO (assuming >> it will only read the GPIO value, not flip the pin to output). > > But I have already stated that this is OK? > > Are we talking past each other now? If all you want to do is prevent gpio_direction_input() on a GPIO that's in use as a GPIO, then that's probably OK. However, the interrupt consistency patch that was posted implemented that restriction by calling gpio_request(), and the wording of most of what you've written implies to me that implementing the restriction by calling gpio_request() is what you're after. That approach imposes far more restrictions than just preventing gpio_direction_input(). Imposing those additional restrictions is what I'm objecting to. -- 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
