Hello Jeff, > it suggests there might be something suspicious going on in the > MappingAvailable - GetMapping logic. It looks like PortCls holds KS_READ/KS_WRITE IRP for some reason. When IRP arrives, PortCls calls MappingAvailable but doesn't return a mapping from GetMapping. Some time later or when another IRP arrives, PortCls calls MappingAvailable again and returns a mapping from GetMapping. > I've only ever observed my problem on Vista - all my WavePCI drivers > on XP have been quite well behaved as far as I'm aware. I suspect this problem is due to DMA_ADAPTER/DmaOperations emulation because my driver is virtual and controls no read hardware. For virtual drivers, DMA logic is emulated by HAL. I implemented my own emulation for 64-bit systems but it follows the same logic. Regards, Eugene ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.com/