VideoPortAllocateCommonBuffer function (video.h)

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

Syntax

VIDEOPORT_DEPRECATED VIDEOPORT_API PVOID VideoPortAllocateCommonBuffer(
  [in]  IN PVOID              HwDeviceExtension,
  [in]  IN PVP_DMA_ADAPTER    VpDmaAdapter,
  [in]  IN ULONG              DesiredLength,
  [out] OUT PPHYSICAL_ADDRESS LogicalAddress,
  [in]  IN BOOLEAN            CacheEnabled,
  [out] OUT PVOID             Reserved
);

Parameters

[in] HwDeviceExtension

Pointer to the miniport driver's device extension.

[in] VpDmaAdapter

Pointer to the VP_DMA_ADAPTER structure that represents the bus-master adapter. This structure was returned by a previous call to VideoPortGetDmaAdapter.

[in] DesiredLength

Specifies the requested number of bytes of memory.

[out] LogicalAddress

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

[in] CacheEnabled

Specifies whether the allocated memory can be cached. For more information, see the description of the CacheEnabled parameter for AllocateCommonBuffer.

[out] Reserved

Is currently ignored by the video port driver; should be set to NULL.

Return value

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

Remarks

When the buffer is no longer needed, the video miniport driver should release it by calling VideoPortReleaseCommonBuffer.

Requirements

Requirement	Value
Minimum supported client	Available in Windows XP and later versions of the Windows operating systems.
Target Platform	Desktop
Header	video.h (include Video.h)
Library	Videoprt.lib
DLL	Videoprt.sys
IRQL	PASSIVE_LEVEL

See also

AllocateCommonBuffer

VP_DMA_ADAPTER

VideoPortGetDmaAdapter

VideoPortReleaseCommonBuffer