NdisAllocateMdl function (ndis/mdlapi.h)
The NdisAllocateMdl function allocates an MDL that describes the memory buffer at the specified virtual address.
Syntax
NDIS_EXPORTED_ROUTINE MDL * NdisAllocateMdl(
[in] NDIS_HANDLE NdisHandle,
[in] PVOID VirtualAddress,
[in] ULONG Length
);
Parameters
[in] NdisHandle
An NDIS handle that was obtained during caller initialization. For more information, see Obtaining Pool Handles.
[in] VirtualAddress
A pointer to the base virtual address of the buffer that the MDL is to describe.
The VirtualAddress parameter for NdisAllocateMdl only accepts memory from the nonpaged pool. In other words, it requires memory from ExAllocatePool*(NonPagedNx), NdisAllocateMemoryWithTagPriority, or NdisMAllocateSharedMemory. In particular, it should not be used with memory from the stack, paged pool, driver global data, or other memory regions.
If a driver needs to build an MDL for one of these non-nonpaged pool regions, it should use the appropriate kernel APIs for that type of memory, such as IoAllocateMdl combined with MmProbeAndLockPages.
[in] Length
The size, in bytes, of the memory buffer.
Return value
NdisAllocateMdl returns a pointer to the allocated MDL. If the allocation fails, the return value is NULL.
Remarks
All MDLs that are allocated by calling NdisAllocateMdl must be freed by calling the NdisFreeMdl function.
NdisAllocateMdl allocates memory and builds the MDL in one step. This process is different from IoAllocateMdl, which only allocates memory for the MDL, meaning the caller must build the MDL by calling either MmBuildMdlForNonPagedPool or MmProbeAndLockPages.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Supported in NDIS 6.0 and later. |
| Target Platform | Universal |
| Minimum UMDF version | 2.33 |
| Header | ndis/mdlapi.h (include ndis.h) |
| Library | Ndis.lib |
| IRQL | <= DISPATCH_LEVEL |
| DDI compliance rules | Irql_NetBuffer_Function(ndis), NdisAllocateMdl(ndis) |