Re: Why no interrupt priorities?

[Richard B. Johnson]

On Fri, 27 Feb 2004, Chris Friesen wrote:

> Grover, Andrew wrote:
>
> > If a device later in the handler chain is also interrupting, then the
> > interrupt will immediately trigger again. The irq line will remain
> > asserted until nobody is asserting it.
>
> I thought I saw examples of edge-triggered shared interrupts earlier in
> the thread.  Doesn't that give the reason for this behaviour?
>
> Chris
>
> --
> Chris Friesen                    | MailStop: 043/33/F10
> Nortel Networks                  | work: (613) 765-0557
> 3500 Carling Avenue              | fax:  (613) 765-2986
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In the early IBM/AT, there was a port to which a user of
a shared "edge" interrupt could write. If the interrupt
line was still asserted, this would generate another edge.

This meant that any ISR needed to know about other users
of the same interrupt. This is probably why it didn't
catch on.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
            Note 96.31% of all statistics are fiction.


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