usbHub.getAttachedUsbDevices() returns 0 with HEAD JNI.
I have build javax-usb-ri-linux from the CVS head on kernel 18.104.22.168 (which needs modifications on kernel header mod_devicetable.h before compiling, but this is probably a kernel issue). This build does not return any usb devices at all, only the hubs in the showtopology example.
Reverting the JNI lib to tag 1.0.1 solves the problem. My best guess it has something to do with the changes in /proc/usb paths which I see in a revision compare.
I you need more information, contact me at r.vandermeer-at-gmail-com.