The function comedi_find_subdevice_by_type() tries to locate a subdevice belonging to comedi device device, having type type, starting with the subdevice start_subdevice. If it finds a subdevice with the requested type, it returns its index. If it does not locate the requested subdevice, it returns -1 and sets the Comedilib error number to XXX "subdevice not found". If there is an error, the function returns -1 and sets the appropriate error.