Unbreak slot_irq_handler(). The problem here is that slot_irq_handler() abuses its argument, which is supposed to be an integer unit number, as a pointer to the head of the 'struct slot' list. When this code was hacked^Wupdated for newbus, a new mechanism for registering slot_irq_handler() was put in place and the significance of the unit number was overlooked. When registering an interrupt, we have both device_id and unit. The unit number is passed as 'unit' but /sys/i386/usa/intr_machdep.c:register_intr() drops unit on the floor and uses device_id instead. Since pccard_alloc_intr() always sets device_id to 0, this means the unit number is always zero, and slot_irq_handler() is always called with 0, which becomes a NULL pointer which slot_irq_handler() tries to dereference and the kernel explodes.
Unbreak slot_irq_handler(). The problem here is that slot_irq_handler()
abuses its argument, which is supposed to be an integer unit number, as
a pointer to the head of the 'struct slot' list. When this code was
hacked^Wupdated for newbus, a new mechanism for registering slot_irq_handler()
was put in place and the significance of the unit number was overlooked.
When registering an interrupt, we have both device_id and unit. The unit
number is passed as 'unit' but /sys/i386/usa/intr_machdep.c:register_intr()
drops unit on the floor and uses device_id instead. Since pccard_alloc_intr()
always sets device_id to 0, this means the unit number is always zero, and
slot_irq_handler() is always called with 0, which becomes a NULL pointer
which slot_irq_handler() tries to dereference and the kernel explodes.

Result: if you assign a PCMCIA driver in the kernel config file like this:

device wi0 at isa? port? irq?

Then the system will panic the moment a PCMCIA device is attached and
an interrupt is triggered.

The quick fix: make pccard_alloc_intr() pass the unit number as both
the device_id and unit arguments to register_pcic_intr(). The correct fix
would be to rewrite /sys/pccard to be less disgusting.

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