This read-only enum reports the role of the Matrix module this switch is attached to: primary(1) or secondary(2) for redundant Matrix modules, none(3) if the switch isn't connected to a Matrix at all, or failed(4) if the Matrix has malfunctioned. An admin polls this after a Matrix module swap to confirm the new module has taken over as primary(1) rather than staying at failed(4). Seeing none(3) on a switch that's supposed to be in prostack-matrix mode points straight at a bad Matrix cable or slot.