Hello,
Current serial.sys is stable for reading from the serial port. Writing works but is synchronous (ie never returns STATUS_PENDING and you can't use overlapped I/O in Win32) Flow handling is not implemented (XON/XOFF) Stopping/removing a serial port when running the system is not implemented yet A few other things, which are probably not important, except one (according to http://www.wd-3.com/archive/SerialFilter.htm): The WaitMask can be set with IOCTL_SERIAL_SET_WAIT_MASK, but IOCTL_SERIAL_WAIT_ON_MASK is not implemented yet. I can take a look at it if you want.
It's committed in revision 23712. http://www.reactos.org/archives/public/ros-diffs/2006-August/013843.html
Regards,
Hervé