IDMAChannel::RequestTransfer (Windows Embedded CE 6.0)

1/6/2010

This method sets up the DMA transfer of a contiguous memory segment with a given physical address and length. After the transfer has been set up, it returns the current number of pending requests.

Syntax

HRESULT RequestTransfer(
  PHYSICAL_ADDRESS physStart,
  DWORD dwSize, 
  VOID* pva,
  DWORD* pdwPending
);

Parameters

• physStart
  [in] Physical address of the memory segment to be transferred.

• dwSize
  [in] Size, in bytes, of the memory segment to be transferred. This value should not exceed the maximum size specified by IDMAChannel::GetMaxOutstandingTransfers.

• pva
  Virtual address of the memory segment to be transferred.

• pdwPending
  [out] Returns the number of pending requests after this request is placed. This value can be NULL.

Return Value

The following table shows a list of possible return values.

Return value	Description
S_OK	The request completed successfully.
E_INVALIDARG	An invalid argument was encountered.
E_UNEXPECTED	The queue is full.

Remarks

It must be confirmed prior to calling this method that there is room in the channel to place a transfer request.

Notification that a transfer has been completed is done not on the basis of individual transfer completion, but on reaching a low-water threshold. You can use the callback in IDMAChannel::SetDataNotificationThreshold.

Requirements

Header	dvddrvr.idl
Windows Embedded CE	Windows CE .NET 4.0 and later

See Also

Reference

IDMAChannel
IDMAChannel::GetMaxOutstandingTransfers
IDMAChannel::SetDataNotificationThreshold