When I try to start the io-usb-dcd server, it looks good:
# io-usb-dcd -dusbser-mx6sabrelite-ci ioport=0x02184100,irq=73

until I look at the system log where irq is logged as an unknown option
# sloginfo
Time             Sev Major Minor Args
Jan 01 00:00:08    2    12     0 mx6sabrelite_extra_process_args_callout : unknown option - irq=73
Jan 01 00:00:08    2    12     0 io-usb : Error Initializing Host Controller

However, if I run the server command without the irq option:
# io-usb-dcd -dusbser-mx6sabrelite-ci ioport=0x02184500

It knows something is missing as I get:  
Must specify irq with ioport option

I feel like I am chasing my tail. Any clues?
thanks