and see if anything responds. if nothing (that's attributable to the
PCI IDE controller) responds, then that channel either has no devices on
it or has been disabled (via a non-standard mechanism) by the BIOS. If nothing
responds, don't map the compat.-mode interrupt or attach the wdc to that
channel, because the BIOS is likely to assign that IRQ to a different PCI
device. If that happens, the kernel will panic because that device will
try to map the IRQ level-triggered, but the compat interrupt will have been
mapped edge-triggered. (One possible way around this is to map the compat
interrupt edge-triggered, but it's not clear reading the spec that this
is correct or desirable.)
insert a check to see whether a channel appears to be enabled. Shouldn't
be necessary, according to the spec, but some PC chipsets allow individual
compatibility channels to be disabled. "I hate PCs."
thorpej