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VideoPortDoDma function

The VideoPortDoDma function is obsolete in Windows 2000 and later.

VideoPortDoDma causes the miniport driver's HwVidStartDma function to be called.

Syntax


PDMA VideoPortDoDma(
  _In_  PVOID HwDeviceExtension,
  _In_  PDMA pDma,
  _In_  DMA_FLAGS DmaFlags
);

Parameters

HwDeviceExtension [in]

Pointer to the miniport driver's device extension.

pDma [in]

Specifies a non-NULL DMA handle. This handle was obtained from a prior call to VideoPortDoDma or from the OutputBuffer member of the VIDEO_REQUEST_PACKET returned by VideoPortLockPages.

DmaFlags [in]

Specifies the action to be performed. This member can be one of the following values:

ValueMeaning

VideoPortKeepPagesLockedVideoPortDmaInitOnly

If possible, the video port driver should keep the memory locked for subsequent DMA operation(s).

VideoPortUnlockAfterDma

The video port driver should unlock the memory after the DMA operation is performed.

 

Return value

VideoPortDoDma always returns NULL.

Remarks

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

Requirements

Version

Available in Windows 2000 and later versions of the Windows operating systems.

Header

Video.h (include Video.h)

Library

Videoprt.lib

DLL

Videoprt.sys

See also

VideoPortLockPages
VIDEO_REQUEST_PACKET

 

 

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