enum DEVICE_RELATION_TYPE

typedef enum _DEVICE_RELATION_TYPE
{
         BusRelations = 0,
         EjectionRelations = 1,
         PowerRelations = 2,
         RemovalRelations = 3,
         TargetDeviceRelation = 4,
         SingleBusRelations = 5
} DEVICE_RELATION_TYPE;

Windows Vista Kernel Structures