VideoPortDoDma function

The VideoPortDoDma function is obsolete in Windows 2000 and later.

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

Syntax

VIDEOPORT_API PDMA VideoPortDoDma(
  IN PVOID     HwDeviceExtension,
  IN PDMA      pDma,
  IN DMA_FLAGS DmaFlags
);

Parameters

HwDeviceExtension

Pointer to the miniport driver's device extension.

pDma

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

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

Value Meaning
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

   
Minimum supported client Available in Windows 2000 and later versions of the Windows operating systems.
Target Platform Desktop
Header video.h (include Video.h)
Library Videoprt.lib
DLL Videoprt.sys

See Also

VIDEO_REQUEST_PACKET

VideoPortLockPages