Subject: tty device names for Cyclades Z
To: None <>
From: Bill Studenmund <>
List: tech-kern
Date: 06/01/2000 14:30:24
I'd like some input on what we should do for the naming of the tty devices
for the Cyclades Z device. It's a multi-port serial interface. It comes in
an 8-port version, and another version which uses externally connected
boxes each with 16 ports. Right now you can have 4 such boxes hanging off
of one pci card. So it's real easy to have 128 of these serial ports real
quick, and 256 is not unfeasable.

Right now the tty's are named [dt]tyCZ0000 on up. I have a few concerns
about this. First off, ps only prints the first two letters of a tty
device name which appear after the [dt]ty - thus all of these ports show
up as "CZ". That's not good. Also, I'm not sure if decemal is really the
best solution here. Using something more hex-based, we could cram quite a
lot of tty's into two letters.

So what do we do? One suggestion was to just have all the ps tools print
out the full name. So these tty's show up as CZ0000. That would mean
growing the tty field in ALL programs which show tty info (ps, w, etc.).
Also, I'm not sure if widening these fields would break anything.

My idea is to leave the tt field in these programs at 2 letters, and to
start numbering the Cyclades tty's from tty10. This idea has the advantage
of fitting upto 256 into the system with little change (tty10 -> ttygf).
Of all of the pci ports, only macppc has a tty in this range, tty10. The
latter is for a com serial port on a pcmcia card. Moving it wouldn't be
too bad as it hasn't made it in a release. :-) All the others have tty10
-> ttygf open AFAICT.

I admit the idea's a bit controversial. Using hex isn't common for
tty's. In NetBSD, only tye pty's use hex, sort of (pa -> qf by default, ->
vf in MAKEDEV). The FreeBSD script uses hex by default.

Also, it's a bit unusual to have two different drivers using a similar tty
numbering space. All of the other tty drivers have a differning letter in
there (ttyA0, ttyB1, etc.). But all of these drivers don't have the
possability of having over 100 such tty's installed. :-)

What did the old vaxen do with lots of tty's?


Take care,