linux-kernel - Re: [PATCH] fix return value of i8042_aux_test

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Date:	Thu, 26 Jul 2007 16:38:04 +0200
From:	Vojtech Pavlik <vojtech@...e.cz>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] fix return value of i8042_aux_test_irq

On Thu, Jul 26, 2007 at 09:54:50AM -0400, Dmitry Torokhov wrote:
> Hi,
> 
> On 7/26/07, Fernando Luis Vázquez Cao <fernando@....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?
 
I believe it was needed on PPC.

-- 
Vojtech Pavlik
Director SuSE Labs
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