On Sun, Jul 28, 2013 at 8:06 PM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > On Sun, Jul 28, 2013 at 6:45 PM, Alexander Holler <holler@xxxxxxxxxxxxx> wrote: >> Am 28.07.2013 18:25, schrieb Linus Walleij: >>> On Sun, Jul 28, 2013 at 4:25 PM, Alexander Holler <holler@xxxxxxxxxxxxx> wrote: >>> >>>> By the way, if someone decides to touch omap_hsmmc, the driver wrongly >>>> assumes that 0 is not a valid IRQ number and it doesn't check if >>>> gpio_to_irq() returns a negative value. ;) >>> >>> Zero *is* *not* a valid IRQ number. >> >> Where is that mentioned? > > This has been a major debate in the kernel in recent months, and we are > agreed to remove 0 as a valid Linux IRQ number. The fact that up until > two years ago the ARM kernel allowed it is a historical artifact. > > Please see this article for background: > http://lwn.net/Articles/470820/ > > Which falls back to this posting from Torvalds: > http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-11/7628.html > >> gpio.txt states: >> >> ---- >> Non-error values returned from gpio_to_irq() can be passed to request_irq() >> or free_irq(). They will often be stored into IRQ resources for platform > > While IRQ 0 is not an error, it means that this particular GPIO line > does not have an IRQ, or cannot be translated into an IRQ, and > should not be passed to request_irq(). > > Patches to the documentation is welcome. > >> With the new patches gpio_to_irq() returns 0. > > This is not good. Under which circumstances does that happen? > >> Documentation/IRQ-domain.txt: >> ---- >> The legacy map should only be used if fixed IRQ mappings must be >> supported. For example, ISA controllers would use the legacy map for >> mapping Linux IRQs 0-15 so that existing ISA drivers get the correct IRQ >> numbers. >> ---- >> >> You see the 0 too? > > Is OMAP still using the legacy map? I don't think that works > on any system utilizing the GIC driver. It is called legacy because > it is not supposed to be used :-/ > Not anymore, it was changed recently to use the linear domain mapping instead in commit ede4d7a5 ("gpio/omap: convert gpio irq domain to linear mapping"). The commit message says Reported-by: Linus Walleij <linus.walleij@xxxxxxxxxx> ;-) >> Of ourse, I might be wrong, but you just stated that 0 isn't valid, and >> I would be happy to find a source for your statement. > > See above. > > Yours, > Linus Walleij > -- Best regards, Javier -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
