any harm in allowing only ctrl-Q to restart output?

[David Sherman]

Almost all of the terminals on our UNIX system are VT-100-compatible
Esprit terminals. They have a NO SCROLL key which transmits ctrl-S
and stops terminal output locally. The terminal will only restart on
receipt of a ctrl-Q.

If you press the NO SCROLL key (which, incidentally, is easy to do
by accident on these terminals), UNIX will see the ctrl-S and stop;
but then _any_ key will let UNIX restart, not just ctrl-Q. This means
data can be lost, if you press NO SCROLL, any other key, and then
wait a bit before ctrl-Q -- UNIX starts resending, but the terminal
won't display it until it gets the ctrl-Q (or you press NO SCROLL again).

I'd like to change UNIX to require ctrl-Q (actually t_startc)
to restart output. With our terminals, it can only improve things -
as it is, users have to know to press the NO SCROLL again (or hit
ctrl-Q explicitly). Is this likely to cause any problems anywhere
else?

We're running v7 on a Perkin-Elmer 3220, by the way. The change is
trivial - commenting out two lines in /usr/sys/dev/tty.c.

As an alternative, I'm thinking of creating a new ioctl setting
(TIOCQSTART?) which controls this behaviour, so it's user-settable.
Any comments on that idea?

Dave Sherman
The Law Society of Upper Canada
Toronto
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