Questions on interrupt vector assignment on MPC8641D

[david.hagood at gmail.com]

OK, using 224 as the MPIC interrupt number, and attempting to map it via
irq_create_mapping(0,224) gives me a kernel seg fault:

Unable to handle kernel paging request for data at address 0x00000000
Faulting instruction address: 0xc0016540
Oops: Kernel access of bad area, sig: 11 [#1]
PREEMPT SMP NR_CPUS=2 EP8641A
Modules linked in: Endpoint_driver(+)
NIP: c0016540 LR: c0050b38 CTR: c00163b8
REGS: ef8c1ab0 TRAP: 0300   Not tainted  (2.6.26.2-ep1.10)
MSR: 00001032 <ME,IR,DR>  CR: 24024482  XER: 00000000
DAR: 00000000, DSISR: 40000000
TASK = eedec6a0[60] 'insmod' THREAD: ef8c0000 CPU: 1
GPR00: 00000000 ef8c1b60 eedec6a0 ffffffea 00000000 00000000 c035c17c
000000e0
GPR08: 00400000 00000000 c035c020 00000000 24024422 100a7264 00000000
00000095
GPR16: 00000095 00000000 0000000d 00000124 f102fd98 00000000 c004a4fc
f102c000
GPR24: 0000001a f1038400 00000000 c031e610 fffffffa 00009032 c031e5e0
000000e0
NIP [c0016540] mpic_set_irq_type+0x188/0x1c4
LR [c0050b38] set_irq_type+0x84/0xc8
Call Trace:
[ef8c1b60] [c0050b1c] set_irq_type+0x68/0xc8 (unreliable)
[ef8c1b80] [c001572c] mpic_host_map+0xec/0xf4
[ef8c1b90] [c00064a0] irq_setup_virq+0x60/0x98
[ef8c1bb0] [c00065dc] irq_create_mapping+0x104/0x114
[ef8c1bd0] [f1034798] Endpoint_device_ctor+0x258/0x3b8 [Endpoint_driver]

Reading the source (since these calls don't seem to have any other
documentation), it *looks* like it ought to be valid to call
irq_create_mapping with a null irq_host *host - which is good, since I
can't see anything obvious that would give me some other irq_host (again,
since none of this seems to be documented anywhere).

I am assuming the default host used by the system would be correct.

However, then I get this fault.