Tested on Kubuntu 16.04 64 bit only. I have an application which source is not under my control. It uses some libusb calls which ends up in e.g.:
libusb: error [_get_usbfs_fd] libusb couldn't open USB device /dev/bus/usb/001/031: Permission denied
libusb: error [_get_usbfs_fd] libusb requires write access to USB device nodes.
sudo chmod a+w /dev/bus/usb/001/031
I suggest that you add a new file in
usb.rules. It should have the following contents:
This will make all USB devices readable and writable by all users.
You could also narrow it down to specific USB devices using
idProduct attributes mentioned in Ignacio's answer.