Re: APIC, changing level/edge interrupt

Pierre Ossman
2005-01-01T21:22:47Z

Tim Hockin wrote:

>Of course. My point was that if it does not, it's a bug in the BIOS.
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Something Windows doesn't seem to be affected by so I don't think we'll
get much help fixing the bios.

>>But since BIOS can configure the APIC then the kernel should be able to
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>Of course, but the kernel has no way to know whether a device should be
>edge or level triggered unless you have a driver for that device. And
>even if you do, I don't know that there is an API in kernel to say
>set_irq_mode(IRQ_EDGE) (though there could be).
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There are some calls in the ACPI layer which plays with the level/edge
stuff but they don't seem very generic. Besides, what I want right now
is just some possibility of confirming that this level/edge business is
the cause of all these problems.

>>What is the default mode and what does the XT-PIC expect? (it works fine
>>with the apic disabled).
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>I think default is PIC-compatible which is edge by default. I think. I
>don;t have the book here.
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Ok. The default from the device is level mode which works fine on PIC
systems. I'm not sure that the hardware actually respects this bit
because level/pulse mode doesn't make any difference on either PIC or
APIC systems.

Rgds
Pierre