MmMapIoSpace function (wdm.h)

The MmMapIoSpace routine maps the given physical address range to nonpaged system space.


PVOID MmMapIoSpace(
  [in] PHYSICAL_ADDRESS    PhysicalAddress,
  [in] SIZE_T              NumberOfBytes,


[in] PhysicalAddress

Specifies the starting physical address of the I/O range to be mapped.

[in] NumberOfBytes

Specifies a value greater than zero, indicating the number of bytes to be mapped.

[in] CacheType

Specifies a MEMORY_CACHING_TYPE value, which indicates the cache attribute to use to map the physical address range.

Return value

MmMapIoSpace returns the base virtual address that maps the base physical address for the range. If space for mapping the range is insufficient, it returns NULL.


A driver must call this routine during device start-up if it receives translated resources of type CmResourceTypeMemory in a CM_PARTIAL_RESOURCE_DESCRIPTOR structure. MmMapIoSpace maps the physical address returned in the resource list to a logical address through which the driver can access device registers.

MmMapIoSpace should only be used with pages that are locked down (belong to the locked pages of an MDL or I/O space), otherwise the owner of the memory could free it (or the memory could be paged in/out, etc.).

For example, drivers of PIO devices that allocate long-term I/O buffers can call this routine to make such buffers accessible or to make device memory accessible.

For more information about using this routine, see Mapping Bus-Relative Addresses to Virtual Addresses.


Target Platform Universal
Header wdm.h (include Wdm.h, Ntddk.h, Ntifs.h)
Library NtosKrnl.lib
DLL NtosKrnl.exe

See also