[haiku-development] Re: Free irq

Simon Taylor <simontaylor1@xxxxxxxxxxxx> wrote:
> On 16/10/11 09:44, Axel Dörfler wrote:
> > On 10/15/2011 06:30 PM, Stefano Ceccherini wrote:
> >> "If a timer is set for edge-triggered mode, the timers should not
> > > be
> >> shared with any PCI interrupts."
> >
> > That sounds plain wrong. Edge triggered is what should be used for
> > shareable interrupts (or for all interrupts, anyway, since it's not
> > possible to miss one).
>
> At least according to wikipedia, the original PCI standard mandates
> shareable level-triggered interrupts.

Yes, level triggerd interrupts are shareable: As long as at least one
device has a pending interrupt the level is kept asserted, hence
multiple devices can signal at the same time and all will be serviced
until the level isn't asserted anymore. The problem that this brings is
that when a driver doesn't properly make the device un-assert the line,
an endless interrupt storm will happen.

Regards
Michael

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