Re: Am I just crazy...?

[Peter Jones <pjones@redhat.com>]

On Fri, 26 Mar 1999, Jakub Jelinek wrote:

> > [pjones@bart 01]$ od -tx1 -Ax 03.0 
> > 000000 95 10 46 06 05 00 80 02 03 8f 01 01 00 40 00 00
> > 000010 01 00 c0 00 09 00 c0 00 11 00 c0 00 19 00 c0 00
> > 000020 21 00 c0 00 00 00 00 00 00 00 00 00 95 10 46 06
> > 000030 00 00 00 00 00 00 00 00 00 00 00 00 00 01 02 04
> > 000040
> > 
> > That says its on IRQ 4, right?  (I'm actually somewhat unsure that its not
> > saying IRQ of 02, becuase there appears to be some byte order wierdness
> > here) 
> 
> PCI_INTERRUPT_LINE is at offset 0x3c, AFAIK, so it is IRQ_LINE 0, IRQ_PIN 1, 
> I think.

OK, right.  That makes sense.  I had been looking at a book that appears
to be fairly accurate regarding PCI, but doesn't really take byte ordering
into account as much as it should.  You're right, include/linux/pci.h
says its at 0x3c.

> But really, interrupts are not so straightforward on sparc64.
> PCI bridge sends interrupt packets with identification which
> device/function/pin is pending (and btw you can disable/enable each such
> pin individually), so this is the second interrupt number (called INO), then
> Linux receives a IRQ trap and based on this INO finds out which interrupt to
> post, thus a third and final irq number comes in, this one is called PIL
> (and this is the number you see in /proc/interrupts) and queues that PIL for
> delivery.

Oh.  Well, ok, that kindof makes sense.  It explains why I'm seeing
numbers that don't seem related, at least ;)  Thanks.

> Cheers,
>     Jakub