Disabling an arbitrary device

[Arnaud Lacombe]

Hi,

I will be bringing up an old thread there, but it would seem the
situation did not evolve in the past 9 years. I have a machine running
7.1 whose UHCI controller is generating some interrupt storm:

# vmstat -i
interrupt                          total       rate
irq4: sio0                          1328          2
irq19: uhci1+                   63514509      96380
[...]

generating useless load on one CPU:

# top -SH
last pid:  5223;  load averages:  0.00,  0.00,  0.00    up 0+00:17:21  13:10:35
117 processes: 14 running, 79 sleeping, 24 waiting
CPU:  0.2% user,  0.0% nice,  0.2% system,  6.6% interrupt, 93.0% idle
Mem: 33M Active, 9348K Inact, 67M Wired, 400K Cache, 29M Buf, 2892M Free
[...]
   57 root          -64    -     0K     8K CPU0   0  11:59 86.57% irq19: uhci1+

I thought I could use an hint to forbid uhci(4) attachment, ala:

hint.uhci.0.disabled="1"
hint.uhci.1.disabled="1"

in /boot/loader.conf. However, it would seem that what should be
usable with any arbitrary devices, ie. be an integral part of
device(9), has to be hardcoded in every driver, sad.

 - Arnaud

ps: the original thread I found is from September 2004:
http://lists.freebsd.org/pipermail/freebsd-questions/2004-September/058717.html