TANDEM mode bugs in 4.3bsd

[Brian Kantor]

In article <973 at tymix.UUCP> feldman at tymix.UUCP (Steve Feldman) writes:
>Description:
>	There are two problems in the TANDEM mode handling in the
>	4.3 bsd tty driver.  (They were in 4.2 as well.)
>
>	First, if you have a device which is slow responding to
>	a control-S, the driver can send additional control-S's
>	when the last few characters arrive.

This may not be a bug, depending upon how you view it.  It is ALSO
possible for the remote device to lose the XOFF character which means
that you MUST send it again or it will NEVER stop.  Very very few devices
queue an incoming XOFF, which means that extra ones don't hurt and are
likely more often to help.

Conjecture:
What may have prompted this is using terminal i/o with TANDEM set to
communicate with some other computer system which does not obey the same
XOFF/XON semantics as Unix does.  CP/M systems, for example, use XOFF to
stop output, but will restart it again on ANY character, including
another XOFF.  In this situation, the behaviour of TANDEM is not
optimal.  But the real solution may be to fix the remote host/device.

	Brian Kantor	UCSD Office of Academic Computing
			Academic Network Operations Group  
			UCSD B-028, La Jolla, CA 92093 USA