Hello, I have added a new test to frontend/tstbackend . When enabled, the tstfrontend program loops calling sane_get_devices() function and print detected devices each second, until a given time elapsed. This way you can plug/unplug/replug scanners and see if they are correctly reported. For instance: ./tstbackend -l0 -r1 -dgt68xx -g35 loops 35 seconds getting devices from gt68xx backend.
I have used it to check and fix device detection of the gt68xx. This backend, like quite a number of USB backends built its device list only in sane_init(), which was wrong, it must be done each time sane_get_devices() is called. Failure to do so prevent the backend from correctly handling hotplug/unplug of scanners. The gt68xx is now fixed regarding this issue. Regards, Stef