USB / udev only work for root

[Sarah Messer <ikustosu@yahoo.com>]

Hello,

I can only communicate with a USB device using libusb when I'm logged in as root.  I reported this previously for libusb-0.1.12, and have since tried upgrading to libusb-1.0 with the libusb-compat patch.

My system:
OpenSUSE 10.3, i386
communication is with a Tektronix TDS2014B oscilloscope using pyusb (a Python wrapper for libusb-0.1)
udev version 114-19

The problem is not present on an OpenSUSE 10.0 machine running identical code with straight libusb-0.1/pyusb

/etc/udev/rules.d/55-libsane.rules contains the following lines (among many others):

# ENV{DEVTYPE}="usb_device", NAME="bus/usb/$env{BUSNUM}/$env{DEVNUM}", MODE="0664", OWNER="root", GROUP="root"

SUBSYSTEM="usb", ACTION="add|change", SYSFS{idVendor}="0699", SYSFS{idProduct}="0368", GROUP="usb", MODE="0664"

The 'scope's /dev/bus/usb/ entry looks like:
crw-rw-r-- 1 root usb  189, 132 2009-01-02 17:09 005

The non-root user who tried to use this scope is a member of these groups:
users dialout uucp video usb

Further notes:
1)  Other USB devices which aren't being accessed via libusb are accessible to non-root users (e.g. printer, thumbdrive)
2)  System seems to require an external hub between the scope and PC for reliable communication, but I _think_ that's a separate hardware issue since it's present on both machines.
3)  The exact error message is "error sending control message: Operation not permitted"
4)  I can get an (apparently valid) DeviceHandle, but both reset() and getString() calls fail - with permissions as the cited reason.

Any guidance you can provide on the likely source of the problem (or troubleshooting tricks) would be welcome.

Thanks

-Sarah