Dear Maintainer, The maximum allowed speed of mgetty is 460800 bauds. There are some serial adapters that can reach higher speeds like 3 Mbauds. Other serial communication programs such as agetty or minicom allow up to 4 Mbauds. It would only be necessary to add the speeds between 460800 bauds and 4000000 bauds to the tio.c and gettydefs.c files.