VideoPortDoDma function (video.h)
The VideoPortDoDma function is obsolete in Windows 2000 and later.
VideoPortDoDma causes the miniport driver's HwVidStartDma function to be called.
Syntax
VIDEOPORT_DEPRECATED VIDEOPORT_API PDMA VideoPortDoDma(
[in] IN PVOID HwDeviceExtension,
[in] IN PDMA pDma,
[in] IN DMA_FLAGS DmaFlags
);
Parameters
[in] HwDeviceExtension
Pointer to the miniport driver's device extension.
[in] 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.
[in] 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
| Requirement | Value |
|---|---|
| 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 |