windows - How to call MmGetPhysicalMemoryRanges in driver to get memory range? -

i writing driver in want exact range of ram. came know memory manager routines inside windows kernel. planning include mmgetphysicalmemoryranges routine in driver memory range. don't know how add these routines driver.. please tell me how write routine??what syntax???

ntkernelapi  pphysical_memory_range  mmgetphysicalmemoryranges (  void  ); 

where physical_memory_range is:

typedef struct _physical_memory_range {  physical_address baseaddress;  large_integer numberofbytes;  } physical_memory_range, *pphysical_memory_range;