The kernel doesn't really have any way to change the physical
device/slot to IRQ mapping. In some cases there are BIOS settings which
might influence this, but in most cases it's impossible to change (i.e.
Thanks for your quick reply. I know there are 4 physical interrupt
lines, interleaved for the many devices connected to a bus, so that, if
most of the devices issue INTA, the interrupts are actually asserted on
different pins of the apic (an almost uniform distribution of the
interrupts, but still, two devices can share the same physical line). I
also know that it's possible to change the (logical) irq levels assigned
to physical INTA-INTD (perhaps using the pirq= parameter).
As I have limited knowledge of hardware implementations, I'm asking you
if it's usual/possible for a dual-processor system to have the same
physical irq pin connected to the same irq line of _different_ pci
buses. To put it in other words, is it possible for two devices on
_separate_ pci buses to physically share the same irq pin?
Most of the systems I've seen with multiple PCI buses (servers, mostly)
have normally had separate IRQ pins for each slot for at least INTA, in
fact. However, I don't think there's any reason why you couldn't have
the same IRQ pin routed to slots on different buses..