Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Driving Parameter
DRIVERTAG_DRIVERPARAMETERParameter: Use Direction
DRIVERTAG_DRIVERVECTORMODEParameter: Min
DRIVERTAG_DRIVERVECTORMINParameter: Max
DRIVERTAG_DRIVERVECTORMAXParameter: X Resolution
DRIVERTAG_DRIVERGRIDXParameter: Y Resolution
DRIVERTAG_DRIVERGRIDYParameter: Clamp
DRIVERTAG_CLAMPParameter: Driven Object
DRIVERTAG_DRIVENOBJECTParameter: Mode
DRIVERTAG_MODEParameter: Parameter
DRIVERTAG_DRIVENPARAMETERParameter: Mix
DRIVERTAG_DRIVERMIXParameter: Relative
DRIVERTAG_DRIVERRELATIVEParameter: Method
DRIVERTAG_ABSMODEParameter: Min
DRIVERTAG_DRIVERMINParameter: Max
DRIVERTAG_DRIVERMAX