delay before open() works

[Brian Craft <bcboy@thecraftstudio.com>]

Hi -- I notice in 2.4 kernels that there's a delay between completion of
"modprobe scanner" and when the device file can be successfully opened. I'm
working on code to power-up devices on-demand.

I've played some with making scripts to work around this, like

  heyu turn on scanner
  modprobe scanner
  sleep 15
  xsane

This is pretty gross, since I have to determine the "15" by playing with it,
and I'm sure it will fail some of the time unless I make it reeeeeally long. I
suspected this was some hardware issue -- USB latencies on device discovery, or
boot time for the scanner -- but a friend who isn't attempting to power-up his
devices says he sees the same behavior when just scripting "modprobe". So it
appears there's some fairly long delay in the kernel itself.

Anyone know off-hand what causes this delay, or if there's some way to get
the open() to block?

(btw, I'm not subscribed to the list).
b.c.