It really doesn't matter. CopyTo and CopyFrom are essentially the same function, just a generic data copy helper (has optimized assembly code on x86 and calls RtlCopyMemory on non-x86). You just need to pick the appropriate Destination and Source addresses when you call it. Ken From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Yong Liu Sent: Thursday, February 15, 2007 6:27 AM To: wdmaudiodev Subject: [wdmaudiodev] question about copyto and copyfrom I am some confused in using IDmaChannel::copyto and copyfrom. I am writing a virtual wdm audio catpute driver, since it is a virtual driver, the audio data is not from a real device, it is from an application. Which function copyto or coypfrom I should use to send the data to the driver? Thank you very much. Yong