USB class hotplug confusion

[Andrey Borzenkov <arvidjaar@mail.ru>]

Since some time running -mm produces

cat: /sys//class/usb/lp0/bNumConfigurations: No such file or directory
/etc/hotplug/usb.agent: line 144: [: too many arguments

there is no wonder as

{pts/2}% l /sys/class/usb/lp0
dev  device@  driver@

apparently in addition to "normal" USB events we get extra class
events; I must admit I do not understand what "class" is for and why
usblp is using it but e.g. joystick (that I have as well) does not.

Is there simple way to simply ignore those events in usb.agent? Or
better yet - is it possible to specify different agents for "device" and
"class" events? As kernel provides both they are presumed to be
different and require different actions?

-andrey