Am 25.07.2014 13:38, wrote Linus Walleij: > On Thu, Jul 24, 2014 at 10:12 AM, Markus Niebel > <list-09_linux_arm@xxxxxxx> wrote: >> Am 23.07.2014 18:14, wrote Linus Walleij: > >>> So always prepare the hardware and make it ready for action in respective >>> callbacks from the GPIO and irqchip APIs. Do not rely on gpiod_to_irq() having >>> been called first. >>> >> >> So a gpio driver is responsible to read status of gpio lines and flag any gpio line >> currently configured as out (base on the information read from hardware registers) >> on driver probe time - correct? > > I don't think anyone reads that information explicitly to set up > these flags. > > Drivers just leave the pins in their power-on maiden state without > trying to figure out how they're set-up. But as you say, if you call > gpiod_get_direction() on them, the flag gets set up indeed. > > So usually these flags are set by code, calling > gpiod_[get/set]_direction(). > Then they do get flagged as outputs or inputs. > >> If yes is the driver allowed to call >> gpiod_get_direction() to have the FLAG_IS_OUT set in the gpiolib layer? > > I don't know if it'd be a good idea to loop over all gpios in a new > irqchip and fetch the direction just to get the flags right, so far > we haven't done that and I don't know what the usecase would be. > I've came to a situation where it would have been helpful to know - bootloader configured a pin as output and linux tried to configure the pin as IRQ input. *YES I KNOW THIS IS NOT CORRECT* but it took some time to see, what happened. > If we need that we should do it in gpiolib for all drivers don't you > think? A pragmatic / lean solution would be to deny the IRQ configuration when seeing the pin configured as output in hardware and print out an error on the gpio driver level. > > But then we need a rationale for doing it, other than it's nice :-) > It is already called on-the-fly by debugfs when a user needs that > info. See above, I think an error on a misconfigured system would be enough. Maybe the documentation for gpio drivers should have a hint for driver implementors. So first step would be to convert the driver to the irqchip helper and then add calls to gpiod_[un]lock_as_irq at the right places. Will try to do that after my holiday. > > Yours, > Linus Walleij > Yours, Markus Niebel -- 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
