On Mon, Sep 23, 2013 at 10:21 PM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > On 09/23/2013 02:01 PM, Linus Walleij wrote: >> And how to you block the same line from being gpio_request()ed >> and set as output? > > To be honest, I really don't think this problem is terribly likely to > occur, so I'm really not convinced that it's worth putting a lot of > effort into solving it. I have a different opionion, I think this is important. As GPIO subsystem maintainer I need to be convinced of the integrity of the system. > If the problem does occur, it's trivial to see that this has happened by > looking at /proc/interrupts and /sys/kernel/debug/gpio, I basically want /sys/kernel/debug/gpio to say if a certain line is tied for IRQ. > That driver needs to maintain some state that indicates which of its > IRQs have been requested. Any time a GPIO request (I mean e.g. > set_output() not request_gpio)) comes in, the request needs to be > validated against that IRQ usage state. If there's a conflict, deny the > GPIO request. I think this should be done by gpiolib, and I think it is trivial given the right APIs. Putting it in the drivers will just create an array of similar-look Rube Goldberg-machines and code duplication. There is no point. > Now, it's quite possible that the code to maintain this state and > perform the checks will be similar/common across multiple drivers. If > so, by all means implement the code somewhere common, and have the > various irq_chip/gpio_chip drivers call into it. And this is what we should do in gpiolib. > The main thing is that all of this has to be driven/controlled/enabled > by the gpio_chip/irq_chip driver itself, not as some global/blanket > feature of the GPIO or IRQ subsystems. Sure. > Perhaps rather than having the gpio_chip/irq_chip drivers physically > implement a function which calls this common code, they could set some > flags/data/... in the struct gpio_chip/irq_chip indicating that they > desire the core code that implements the error-checking to be enabled. I think it should more be like a function they can call to flag a GPIO as used for IRQ. Yours, Linus Walleij -- 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
