more usb keyboard (and mouse) troubles with 6.X

FreeBSD dirk.no.domain 6.0-RC1 FreeBSD 6.0-RC1 #0: Tue Oct 11 15:51:46
EST 2005     sam_at_dirk.no.domain:/usr/src/sys/i386/compile/GENERIC  i386

This one is interesting.

I have two USB keyboard/mouse combination devices here:

- An IBM (0x04b3) IBM Standard USB Keyboard (0x3001).
  Mouse has 2 buttons + Z-dir.
- And a Belkin wireless which shows up as something generic
  (vendor 0x05fe device 0x1010). Mouse has 5 buttons + Z-dir.

The IBM setup works fine.  No troubles in console or X, both kbd and
mouse work as expected.

The Belkin setup works OK initially.  But as soon as I move the mouse,
all keyboard and mouse input is locked up.  The system is not frozen -
if I reboot, run top and repeat, it continues to run and shows
nothing ominous. The result is the same in console or X.

Since the IBM works, I guess something about the Belkin is tickling a
fairly specific problem somewhere.  A ktrace of moused shows:

   265 moused   0.000000 RET   select 1
   265 moused   0.000204 CALL  read(0x3,0xbfbfe73f,0x1)
   265 moused   0.000221 GIO   fd 3 read 1 byte
       0x0000 83                                                           |.|

   265 moused   0.000292 RET   read 1
   265 moused   0.000294 CALL  select(0x400,0xbfbfe780,0,0,0)
   265 moused   0.000296 RET   select 1
   265 moused   0.000298 CALL  read(0x3,0xbfbfe73f,0x1)
   265 moused   0.000301 GIO   fd 3 read 1 byte
       "\0"

   (6 more of the previous block)

   265 moused   0.000302 RET   read 1
   265 moused   0.000305 CALL  select(0x400,0xbfbfe780,0,0,0)
   265 moused   0.000307 RET   select 1
   265 moused   0.000309 CALL  read(0x3,0xbfbfe73f,0x1)
   265 moused   0.000312 GIO   fd 3 read 1 byte
       0x0000 7f                                                           |.|

   265 moused   0.000313 RET   read 1
   265 moused   0.000319 CALL  gettimeofday(0xbfbfe6d0,0)
   265 moused   0.000322 RET   gettimeofday 0
   265 moused   0.000331 CALL  ioctl(0x5,CONS_MOUSECTL,0xbfbfe6b0)
   265 moused   0.000354 RET   ioctl 0
   265 moused   0.000357 CALL  select(0x400,0xbfbfe780,0,0,0)
   265 moused   22.376219 RET   select -1 errno 4 Interrupted system call
   265 moused   22.376229 PSIG  SIGTERM caught handler=0x8049874 mask=0x0 code=0x0
   265 moused   22.376322 CALL  exit(0)

You can see I waited about 20 seconds before rebooting.  Lots of
mouse-wiggling and key-bashing in that time to no avail.

Any ideas where to look next?  I'm building a kernel now with debugging
and USB debugging turned on.