Are pre-2.6.15 kernels incompatible with udev?

[David Jarvie <lists@astrojar.org.uk>]

I have updated my etch installation with the latest updates, which include 
kernel 2.6.15 and udev. I find now that when I boot up an older (customised) 
2.6.12 kernel, X fails to start up because it can't find the 
device /dev/psaux which is used for the mouse. Can somebody tell me how I can 
run my older kernel with etch and udev?

I need to run the older kernel because there are as yet no customised patches 
available for 2.6.15 which will allow me to upgrade my customised kernel.

-- 
David Jarvie.