VideoPortGetCommonBuffer function

Description

The VideoPortGetCommonBuffer function is obsolete in Windows XP and later, and is supported only for backward compatibility with existing drivers. In its place, driver writers should use VideoPortAllocateCommonBuffer.

VideoPortGetCommonBuffer allocates and maps system memory so that it is simultaneously accessible from both the processor and a device for common-buffer DMA operations.

Parameters

HwDeviceExtension [in]

Pointer to the miniport driver's device extension.

DesiredLength [in]

Specifies the requested number of bytes of memory.

Alignment [in]

Specifies the requested alignment of the buffer. The video port driver currently ignores this parameter.

LogicalAddress [out]

Pointer to a variable that receives the logical address to be used by the adapter to access the allocated buffer.

pActualLength [out]

Pointer to a variable that receives the actual size, in bytes, of the buffer allocated for this request.

CacheEnabled [in]

Specifies whether the allocated memory can be cached.

Return value

VideoPortGetCommonBuffer returns the base virtual address of the allocated buffer if successful; otherwise, returns NULL if the buffer cannot be allocated.

Remarks

See Bus-Master DMA in Video Miniport Drivers for information about packet-based and common-buffer DMA transfers.

See also

VideoPortAllocateCommonBuffer