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SubjectRe: better leve triggered IRQ management needed

On Sat, 29 Apr 2006, Alan Cox wrote:
> Trying to guess the current IRQ level v edge on a PC is very hard.
> Trying to set it correctly from the driver is rather easier.

I disagree. It's not any easier at all.

On PC's (x86 and x86-64) we actually already set the ELCR as well as we
can (look for "eisa_set_level_irq()"). And a driver _literally_ cannot
change it from the system value, because of the polarity confusion.

In the other cases (IO-APIC) we usually have it level, but when we have it
marked as an edge, there is almost always a real reason for that too (ie
legacy interrupt, it really _is_ edge-high, not level-low).

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