kernel panic with pccard insert on recent 7.0 CURRENT

John-Mark Gurney gurney_j at
Sun Jun 17 08:50:10 UTC 2007

Wilkinson, Alex wrote this message on Sun, Jun 17, 2007 at 15:13 +0800:
>     0n Sat, Jun 16, 2007 at 11:56:59PM -0600, M. Warner Losh wrote: 
>     >Yes.  I'm pretty sure that's wrong.  All ISA and PC Card devices use
>     >edge triggered interrupts.  Also, it is inefficient for level
>     >triggered interrupts, since two interrupt sources on the same
>     >interrupt may trigger at about the same time...
> What is meant by "edge triggered interrupts" ?

Old ISA (edge) interrupts are only noticed when going from low (sometimes
lines are driven opposite, I'm not sure which way ISA interrupt lines
are driven) to high...  This means that if you ack the interrupt, but
the device never lowers the interrupt line, you will never see another
low->high edge, and hence, never another interrupt from that line...

PCI interrupts are level, which means as long as the interrupt line is
"high" an interrupt will be delivered...  This has the disadvantage
that if you can't shut up the device, you get a storm and will need to
disable that interrupt line... 

  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."

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