NdisBufferVirtualAddressSafe (Windows CE 5.0)
This function is the safe version of NdisBufferVirtualAddress. Unlike NdisBufferVirtualAddress, this function will not cause a bug check if system resources are low or exhausted. Drivers should call this function instead of NdisBufferVirtualAddress. NDIS 5.1 miniport drivers must call this function instead of NdisBufferVirtualAddress.
PVOID NdisBufferVirtualAddressSafe(PNDIS_BUFFERBuffer,MM_PAGE_PRIORITYPriority);
Parameters
- Buffer
[in] Points to a buffer descriptor from which the base virtual address is to be returned. - Priority
[in] Indicates the priority of the request as one of the following:LowPagePriority
Specifies a low priority. It is acceptable for NdisBufferVirtualAddressSafe to fail if system resources are low.
NormalPagePriority
Specifies a normal priority. It is acceptable for NdisBufferVirtualAddressSafe to fail if system resources are low.
HighPagePriority
Specifies a high priority. It is not acceptable for NdisBufferVirtualAddressSafe to fail unless system resources are exhausted.
Return Values
The following table shows the values returned from NdisBufferVirtualAddressSafe.
| Value | Description |
|---|---|
| NDISBUFFERVIRTUALADDRESSSAFE | The base system-space virtual address that maps the physical pages described by the given buffer descriptor. |
| NULL | The value returned if system resources are low (if Priority was set to LowPagePriority or NormalPagePriority) or exhausted (if Priority was set to HighPagePriority). |
Remarks
NdisBufferVirtualAddressSafe returns the base virtual address for the buffer mapped by a given buffer descriptor. It maps the physical pages described by the given buffer descriptor onto system space if these pages are not already mapped to system space.
Drivers of PIO devices call this routine to translate a virtual address range, described by the buffer, for a user buffer to a system-space address range.
The returned base address has the same offset as the virtual address in the buffer.
If Priority was set to LowPagePriority or NormalPagePriority, NdisBufferVirtualAddressSafe returns NULL if system resources are low or exhausted. If Priority was set to HighPagePriority, NdisBufferVirtualAddressSafe returns NULL if system resources are exhausted.
Drivers should call NdisBufferVirtualAddressSafe instead of NdisBufferVirtualAddress. If system resources are low or exhausted, calling NdisBufferVirtualAddress causes a bug check. NDIS 5.1 miniports must call NdisBufferVirtualAddressSafe instead of NdisBufferVirtualAddress.
Requirements
OS Versions: Windows CE .NET 4.0 and later.
Header: Ndis.h.
Link Library: Ndis.lib
See Also
NdisAllocateBuffer | NdisAllocateBufferPool | NdisAllocateMemory | NdisBufferVirtualAddress | NdisFreeBuffer
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