autobauding on UNIX?

[smb at ulysses.UUCP]

Has anyone implemented any sort of "autobaud" capability on any version
of UNIX?  That is, I'd like to get away from clumsy mechanisms like
cycling through the speed table.  Many (most?) port selectors and the
like can recognize your speed from a simple CR or some such; has anyone
modified UNIX to do the same?  My guess is that on 4.1/4.2bsd, it would
take changes to getty.c and the tty driver; on 5.0, it might just be
possible to do it all in getty.c.