libusb, nut-ups and Powerware UPS's via USB

[Carl Brewer <carl%bl.echidna.id.au@localhost>]

G'day,
I've just replaced a faulty UPS at a client site with a nice new 
Powerware 5110 UPS, with  ... a USB port.

No worries, nut supports them, or should .. except .. NetBSD's pkgsrc 
libusb doesn't seem to have usb_clear_halt, so even with the current nut 
source (pkgsrc is ancient ... the current release is 2.4.3, pkgsrc is 
2.0.5!) it can't find this UPS :

./bcmxcp_usb -a pw5110 -u root
Network UPS Tools - BCMXCP UPS driver 0.23 (2.4.3)
USB communication subdriver 0.18
Can't reset POWERWARE USB endpoint: usb_clear_halt called, unimplemented 
on BSD
Unable to find POWERWARE UPS device on USB bus (USB)


But it's there, dmesg says so :

ugen0: Powerware Powerware UPS, rev 2.00/0.50, addr 2

and my ups.conf definition is (I think!) correct :

[pw5110]
        driver = bcmxcp_usb
        port = auto
        desc = "PowerWare 5110"
        shutdown_delay = 60


A lot of googling suggests that the (also pretty dated!) libusb 0.1.12 
in pkgsrc doesn't implement usb_clear_halt, which may be a show stopper?

This post suggests a patch for OpenBSD's pkg version :

http://old.nabble.com/Openbsd-and-libusb-td21558254.html#a21558709

Can anyone suggest what I should do to get this UPS running (that 
doesn't include changing OS to some variant of Linux!) with the USP 
interface?

Thanks!

Carl