On Wed, Mar 22, 2000 at 07:24:33PM +0100, Maciej W. Rozycki wrote:
> It looks like a spurious 8259A interrupt detection, i.e. it checks if bit
> 7 of ISR is set. An 8259A feeds a default IRQ 7 to the host whenever no
> IRQ is active upon receipt of an interrupt acknowledge. No ISR bit is set
> in this case.
Anyway, it won't detect spurious interrupts from PIC 2 (IRQ 15).
> The code looks right provided the 8259A is configured to return the
> contents of ISR (Interrupt Service Register) on read by default.
It _is_ configured to IRR at least on lx164 and sx164, so that
code is wrong. And a generic kernel code seems to be relying
on the status read returning IRR - see isa_no_iack_sc_device_interrupt().
So I think the patch I posted is correct because
- spurious interrupts should be harmless for current kernels
- duplicating i386 code for spurious interrupt detection
would buy nothing except the warning about broken hardware
- it would be a pain checking such code on an each possible
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