Kernel panic when loading snd_ai2s module

[Justin Hibbits]

When loading the snd_ai2s module, on both Nathan's livefs (20100418 livefs)
and r207303, I get the following panic (with details):

snapper0: <Texas Instruments TAS3004 Audio Codec> at addr 0x6a on iicbus0
panic: vm_fault: fault on nofault entry, addr: deadc000
KDB: enter: panic
[ thread pid 1741 tid 100145 ]
Stopped at      0x33feb4:       addi    r0, r0, 0x0
db>  where

Tracing pid 1741 tid 100145 td 0xbfea240
0xe5315420: at panic+0x13c
0xe5315470: at vm_fault+0x178
0xe5315590: at trap_pfault+0x174
0xe53155c0: at trap+0x6dc
0xe5315680: at powerpc_interrupt+0x100
0xe53156a0: kernel DSI read trap @ 0xdeadc0de by powerpc_config_intr+0x60:
srr1=0x9032
            r1=0xe5315750 cr=0x40002032 xer=0 ctr=0x1 sr=0x40000000
0xe5315750: at powerpc_config_intr+0x2c
0xe5315770: at aoagpio_attach+0xa8
0xe53157a0: at device_attach+0x338
0xe53157d0: at device_probe_and_attach+0x5c
0xe53157e0: at bus_generic_driver_added+0x90
0xe5315800: at devclass_driver_added+0xac
0xe5315830: at driver_module_handler+0x238
0xe5315860: at module_register_init+0xb8
0xe5315880: at linker_load_module+0x968
0xe5315a50: at kern_kldload+0xcc
0xe5315a80: at kldload+0x70
0xe5315ab0: at trap+0x384
0xe5315b70: at powerpc_interrupt+0x100
0xe5315b90: user SC trap by 0x418b9298: srr1=0xd032
            r1=0x7fffd850 cr=0x40022082 xer=0 ctr=0x418b9290
db> show registers
r0            0x33fea8  kdb_enter+0x54
r1          0xe5315400
r2            0x9d7a80  __pcpu
r3            0x9d7a80  __pcpu
r4                 0xa
r5            0x7ced64
r6                0xdf  dsisize+0x3b
r7            0x9d7d00  ofw_pmap
r8            0x3f168f  inm_release_locked+0x3
r9            0x850000  nd_prefix
r10                0xa
r11         0xe5315400
r12         0x20009034
r13                  0
r14         0xdeadc000
r15           0x86b004  Giant
r16           0x82fd98  linker_hintfile
r17                  0
r18                  0
r19           0x9d6e00  vm_page_queue_lock
r20           0x82f978  M_LINKER
r21           0x7f79ec
r22          0x126c500
r23                  0
r24                  0
r25         0xe53156a8
r26         0xdeadc000
r27          0xbfea240
r28           0x850000  nd_prefix
r29           0x850000  nd_prefix
r30           0x7d07b4
r31         0xe5315400
srr0          0x33feb4  kdb_enter+0x60
srr1            0x9032  dsisize+0x8f8e
lr            0x33feb4  kdb_enter+0x60
ctr                  0
cr          0x40009034
xer                  0
dar                  0
dsisr                0
0x33feb4:       addi    r0, r0, 0x0

Machine details:  PowerMac G4 MDD, 2GB RAM
I can provide more details if necessary.  It's fully reproducible.  I can't
be certain of when it started, as the last build I used regularly was from
February 18 (reinstalled from snapshot CD last weekend), and the sound
driver was compiled into the kernel.  I have not tried compiling the driver
into this kernel.

- Justin