include vcomm.inc
mov edx, Win32_DCB
mov eax, Ring0_DCB
VxDCall _VCOMM_Map_Ring0DCB_To_Win32
The port driver functions PortGetCommConfig and PortSetCommConfig are called from Win32 and use a Win32-style DCB, not a Ring0 DCB. These port driver functions call _VCOMM_Map_Ring0DCB_To_Win32 to convert the DCBs.