MmMapIoSpaceEx function (wdm.h)
The MmMapIoSpaceEx routine maps the given physical address range to non-paged system space using the specified page protection.
Syntax
PVOID MmMapIoSpaceEx(
[in] PHYSICAL_ADDRESS PhysicalAddress,
[in] SIZE_T NumberOfBytes,
[in] ULONG Protect
);
Parameters
[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] Protect
Flag bits that specify the protection to use for the mapped range. The caller must set one of the following flag bits in the Protect parameter.
| Flag bit | Meaning |
|---|---|
| PAGE_READONLY | The mapped range can only be read, not written. |
| PAGE_READWRITE | The mapped range can be read or written. |
| PAGE_EXECUTE | The mapped range can be executed, but not read or written. |
| PAGE_EXECUTE_READ | The mapped range can be executed or read, but not written. |
| PAGE_EXECUTE_READWRITE | The mapped range can be executed, read, or written. |
In addition, the caller can set one (but not both) of the following optional flag bits in the Protect parameter.
| Flag bit | Meaning |
|---|---|
| PAGE_NOCACHE | Specifies non-cached memory. |
| PAGE_WRITECOMBINE | Specifies write-combined memory (the memory should not be cached by the processor, but writes to the memory can be combined by the processor). |
Return value
MmMapIoSpaceEx 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.
Remarks
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. MmMapIoSpaceEx maps the physical address returned in the resource list to a virtual address through which the driver can access device registers.
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.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Available starting with Windows 10. |
| Target Platform | Universal |
| Header | wdm.h (include Wdm.h, Ntddk.h, Ntifs.h) |
| Library | NtosKrnl.lib |
| DLL | NtosKrnl.exe |
| IRQL | <=DISPATCH_LEVEL |