Hello Linus, On Tue, Dec 06, 2011 at 11:20:49AM -0800, Linus Torvalds wrote: > On Tue, Dec 6, 2011 at 2:46 AM, Russell King - ARM Linux > <linux@xxxxxxxxxxxxxxxx> wrote: > > > > But.. let's make one thing clear: Alan Cox and Linus have been going on > > about how IRQ0 should not be used. Let's be crystal clear: even x86 > > uses IRQ0. > > Not for any device driver, though. > > It's used entirely internally, and it doesn't even use > "request_irq()". It uses the magic internal "setup_irq()" and never > *ever* exposes irq0 as anything that a driver can see. > > That's what matters. You can use irq0 in ARM land all you like, AS > LONG AS IT'S SOME HIDDEN INTERNAL USE. No drivers. No *nothing* that > ever uses that absolutely *idiotic* NO_IRQ crap. > > In fact, you may be *forced* to use what is "physically" irq0 - it's > just that you should never expose it as such to drivers. And x86 > doesn't. > > So Russell, if you think this has anything to do with NO_IRQ, and how > x86 isn't doing things right, you're wrong. It's just like the > internal exception thing, or the magical "cascade interrupt", or the > "x87 exception mapped through the PIC". They are magic hidden > interrupts that are set up in one place (well, one place *each*), and > are never exposed anywhere else. Well there is try_misrouted_irq in kernel/irq/spurious.c that assumes irq0 to be something that it never is on ARM (and maybe all other platforms apart from x86). So at least it's not internal to a single (x86 specific) place. I tried to patch that two years ago, but that only ended in people saying "don't use irq0". I don't know if try_misrouted_irq sees hardware irqs, but if it does it's a bug even on archs != X86 that use virtual irqs. (Note that this doesn't oppose to your statement that using NO_IRQ is crap.) > The problem with NO_IRQ is that stupid "we expose our mind-numbingly > stupid interfaces across the whole kernel". > > x86 never did that. ARM still does. x86 doesn't have to fix anything. ARM does. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
