On Wed, Oct 17, 2012 at 8:32 PM, Stephen Warren <swar...@wwwdotorg.org> wrote: > On 10/16/2012 04:33 PM, Stephen Warren wrote: >> On 10/16/2012 01:23 PM, Linus Walleij wrote: >>> The MXS driver tries to do the work of irq_domain_add_linear() >>> by reserving a bunch of descriptors somewhere and keeping track >>> of the base offset, then calling irq_domain_add_legacy(). Let's >>> stop doing that and simply use the linear IRQ domain. >> >> This /looks/ fine, but appears to break users of GPIOs from this module, >> and causes a backtrace when cat /sys/kernel/debug/gpio: > ... > > The following additional diff makes it work: > >> diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c >> index 0234162..c7c175a 100644 >> --- a/drivers/gpio/gpio-tegra.c >> +++ b/drivers/gpio/gpio-tegra.c >> @@ -460,7 +460,7 @@ static int __devinit tegra_gpio_probe(struct >> platform_device *pdev) >> gpiochip_add(&tegra_gpio_chip); >> >> for (gpio = 0; gpio < tegra_gpio_chip.ngpio; gpio++) { >> - int irq = irq_find_mapping(irq_domain, gpio); >> + int irq = irq_create_mapping(irq_domain, gpio); >> /* No validity check; all Tegra GPIOs are valid IRQs */ >> >> bank = &tegra_gpio_banks[GPIO_BANK(gpio)]; > > I wonder if perhaps the entirety of that loop and perhaps the one after > it should be in the IRQ domain's map op - is that how all this is > intended to work?
I've been asking the same kind of question... Basically as far as I understand: - If you use a linear IRQ domain you need to call irq_create_mapping() atleast once, and at that point the IRQ descriptor will be dynamically allocated. On subsequent calls, irq_find_mapping() can be used. - If using legacy IRQ domains, descriptors are supposed to be allocated elsewhere, and you can just use irq_find_mapping(), but irq_create_mapping() does not hurt, because that call will check if a descriptor is already available. - With the simple domain (as augmented by myself) the mappins will be dynamically created if the passed IRQ base is <= 0 else it falls through to creating a linear domain, so in this case to be certain irq_create_mapping() should also be called at least once. I'm not overly happy with these semantics :-( Basically irq_find_mapping() may be a fragile and dangerous optimization path. I've folded the above into my patch. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/