Messages in this thread | | | Date | Thu, 26 Jul 2007 23:39:13 +0900 (JST) | Subject | Re: [PATCH] fix return value of i8042_aux_test_irq | From | fernando@oss ... |
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On Thu, July 26, 2007 10:54 pm, Dmitry Torokhov wrote: > Hi, > > On 7/26/07, Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp> wrote: >> I made an interesting finding while testing the two patches below. >> >> http://lkml.org/lkml/2007/7/19/685 >> http://lkml.org/lkml/2007/7/19/687 >> >> These patches modify the traditional CONFIG_DEBUG_KERNEL in such a way >> that the request_irq prints a warning if after calling the handler it >> returned IRQ_HANDLED . >> >> The code looks like this: >> >> int request_irq(unsigned int irq, irq_handler_t handler, >> unsigned long irqflags, const char *devname, void >> *dev_id) >> ..... >> if (irqflags & IRQF_DISABLED) { >> unsigned long flags; >> >> local_irq_save(flags); >> retval = handler(irq, dev_id); >> local_irq_restore(flags); >> } else >> retval = handler(irq, dev_id); >> if (retval == IRQ_HANDLED) { >> printk(KERN_WARNING >> "%s (IRQ %d) handled a spurious interrupt\n", >> devname, irq); >> } >> ..... >> >> I discovered that i8042_aux_test_irq handles the "fake" interrupt, >> which, in principle, is not correct because it obviously isn't a real >> interrupt and it could have been a spurious interrupt as well. >> >> The problem is that the interrupt handler unconditionally returns IRQ >> handled, which does not seem correct. Anyway I am not very familiar with >> this code so I may be missing the whole point. I would appreciate your >> comments on this. >> > > The handler does handle the interrupt - both status and data registers > are read so from the keyboard controller point of view the interrupt > has been handled even if we happen to discard the data. As far as I > know IRQ12 is never shared by BIOS... Vojtech, do you remember why we > request IRQ12 with IRQF_SHARED? Hi Dmitry,
Thank you for the feedback.
Isn't there a way to tell whether the interrupt came from a different source? If it is not possible the IRQF_SHARED flag does not seem appropriate to me. If we return IRQ_HANDLED unconditionally we may end up preventing the right interrupt handler from executing. Am I missing something?
Fernando
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