As suggested the legacy device count is set to zero. A new module parameter

As suggested the legacy device count is set to zero. A new module parameter
for comedi_fops allows setting the number of legacy devices: comedi_num_legacy_minors. The default is zero.
usbdux and usbduxfast upload now their firmware via the firmware kernel meachanism. No udev rules are needed for that except the default ones. The firmware will usually be loaded from /lib/firmware. Upload via comedi_config is still possible for static comedi devices (comedi_num_legacy_minors>0). Frank, thanks for the example code which sped up rewriting of the code substantially.