The parameter comedi needs to be set to a valid Comedi device handle, i.e., needs to be set to the record member dh of a ComediConfig record instance.
Uses the Comedi function comedi_from_phys(..) to support providing a physical value (volts or milliamps) as input to the DAC. See the Comedi documentation for the meanings of the parameters subDevice, channel, range, aref.
Only supported for Linux, since Comedi is only available for linux (http://www.comedi.org/). Requires that Comedilib is installed and that the simulation process has sufficient privileges to access the intended device (usually that means "root" privileges).