No trace of uevent_helper in udev code. http://git.kernel.org/?p=linux%2Fhotplug%2Fudev.git&a=search&h=HEAD&st=grep&s=uevent_helper No trace of uevent_helper or hotplug in /lib/udev/rules.d/
From http://lwn.net/Articles/166954/ The hotplug helper /sbin/hotplug is now officially deprecated. The control file /proc/sys/kernel/hotplug has moved to /sys/kernel/uevent_helper, but it is expected to be disabled on most systems in favor of udev and the netlink interface.
So this is an old legagy. We should drop it.
Signed-off-by: Sebastien Luttringer