I2C bus probe-able?

[Erik Fair <fair%netbsd.org@localhost>]

A Sun Netra T1 model 200 that I've upgraded to NetBSD 5.0 now says:

alipm0 at pci1 dev 3 function 0: 74KHz clock
iic0 at alipm0: I2C bus
spdmem0 at iic0 addr 0x54
spdmem0: SDRAM memory, data ECC, 512MB, 133MHz (PC-1100)
spdmem0: 13 rows, 11 cols, 1 banks, 4 banks/chip, 7.5ns cycle time
spdmem0: tAA-tRCD-tRP-tRAS: 3-20-20-45
spdmem0: voltage LvTTL (not 5V tolerant), refresh time 7.8us (self- 
refreshing)
[ ... repeat for four more DIMMs ... ]

However, a Sun Blade 150 that I've similarly upgraded to NetBSD 5.0  
doesn't attach spdmem on its RAM at all. I note that the relevant  
section of the GENERIC kernel config says:

# Netra X1 / T1 style environmental monitoring
alipm*          at pci?
iic*            at alipm?
spdmem*         at iic? addr 0x54
spdmem*         at iic? addr 0x55
spdmem*         at iic? addr 0x56
spdmem*         at iic? addr 0x57

And I wonder: is the iic (I2C) bus probe-able, such that we can  
dispense with the specific device addresses, thusly:

spdmem*         at iic? addr ?

Or must we enumerate the iic device addresses for each sparc64 system?

If the latter, it would be nice to have the I2C device address  
discovery procedure documented, and the information collected by each  
of us that has sparc64 hardware, so that we can more completely  
support sparc64 systems.

        Erik <fair%netbsd.org@localhost>