Bug in cac/ld drivers (was: `cannot mount root, error = 79' since upgrade)

[Tom Ivar Helbekkmo <tih%hamartun.priv.no@localhost>]

I wrote:

> Turns out it was data corruption.  How it happened, I don't know, [...]

I do now.  Sometime over the last year, something in the cac and/or ld
drivers must have broken.  Turns out, /dev/*ld0? and /dev/*ld1? are the
exact same devices.  That is, they are different sets of device nodes,
but they access the same (first) actual disk device from the RAID
controller.

I have two such devices:

cac0 at pci0 dev 1 function 0: Compaq Integrated Array
cac0: interrupting at ioapic0 pin 19
cac0: 2 channels, firmware <1.50>
ld0 at cac0 unit 0: standalone disk or RAID0 array
ld0: 34707 MB, 8814 cyl, 128 head, 63 sec, 512 bytes/sect x 71081760 sectors
ld1 at cac0 unit 1: standalone disk or RAID0 array
ld1: 34707 MB, 8814 cyl, 128 head, 63 sec, 512 bytes/sect x 71081760 sectors

This is wrong - ld1 is actually much larger than ld0.  The RAID
controller itself is not confused: its BIOS configuration software shows
everything correctly.  Trying to access /dev/*ld2? doesn't work; "device
not configured" -- so it knows how many devices it has.

-tih
-- 
Self documenting code isn't. User application constraints don't. --Ed Prochak