TTY minor device numbers

[Vernon Schryver]

In article <619 at alias.UUCP>, chk at alias.UUCP (C. Harald Koch) writes:
> What is the difference between the ttyd*, ttym*, and ttyf* devices? What do
> the various bits in the minor device number really do?

ttyd* use RD,TD, and SG RS-232-C fashion. DTR & RTS will be + when the
    device is open, unless HUPCL has been fiddled.
ttym* is the same ttyd*, except that DCD is waited for on open (unless
    NODELAY is set--used by uugetty), and causes SIGHUP and forced-close
    upon a falling edge.
ttyf* is the same as ttym*, except CTS controls output as RS-232-C directs,
    and RTS follows the industry practice, non-RS-232-C-standard flow
    control scheme.  That is, RTS low tells the device to stop talking.

> From scouring the manuals, I have managed to find that ttym* is meant for
> modems, which probably means that an open() call won't return until DCD is
> set. I can't find anything else, other than an obscure reference to the
> Owner's Guide (which doesn't say anything useful).
> -- 
> C. Harald Koch                        Alias Research, Inc., Toronto ON Canada
> chk%alias at csri.utoronto.ca      chk at gpu.utcs.toronto.edu      chk at chk.mef.org

Essentially the preceding words are in text and tables in at least one
of the manuals.  I know because I regularly get the help necessary to find them,
and because we spent lots of memorable time arguing over exactly what would
be enough but not so much as to be confusing.  Unfortunately, I must have
a mental block about where these words are, because I can NEVER find them
without help.

Use ttym for slow modems.  Use ttyf for fast modems which want "hardware
flow control", such as TB's.


Vernon Schryver
Silicon Graphics
vjs at sgi.com