[comp.unix.programmer] ptem's limitations

cat@pluto.dss.com (Iain Wacey) (05/21/91)

of some limitation of ptem. It does not handle flow control
leaving it to any lower module or driver to handle STOPI
messages from ldterm. Ptem also doesn't deal with parity. Has
anyone else run into these problems? If so how did you get around
them? Has anyone written a replacement for ptem that handles these
things. In search of a real psuedo physical terminal.

Iain Wacey
cat@pluto.dss.com

cat@pluto.dss.com (Iain Wacey) (05/21/91)

 I have been using ptem and ldterm to provide a terminal like
Message-ID: <4333@pluto.dss.com>
Date: 20 May 91 20:42:56 GMT
Followup-To: comp.unix.wizards
Organization: Datability Software Systems, New York, NY
Lines: 9
Xref: usc comp.unix.wizards:26796 comp.unix.programmer:1964

of some limitation of ptem. It does not handle flow control
leaving it to any lower module or driver to handle STOPI
messages from ldterm. Ptem also doesn't deal with parity. Has
anyone else run into these problems? If so how did you get around
them? Has anyone written a replacement for ptem that handles these
things. In search of a real psuedo physical terminal.

Iain Wacey
cat@pluto.dss.com

cat@pluto.dss.com (Iain Wacey) (05/21/91)

 I have been using ptem and ldterm to provide a terminal like
Message-ID: <4333@pluto.dss.com>
Date: 20 May 91 20:42:56 GMT
Followup-To: comp.unix.wizards
Organization: Datability Software Systems, New York, NY
Lines: 9
Xref: arizona comp.unix.wizards:1890 comp.unix.programmer:1925

of some limitation of ptem. It does not handle flow control
leaving it to any lower module or driver to handle STOPI
messages from ldterm. Ptem also doesn't deal with parity. Has
anyone else run into these problems? If so how did you get around
them? Has anyone written a replacement for ptem that handles these
things. In search of a real psuedo physical terminal.

Iain Wacey
cat@pluto.dss.com

cat@pluto.dss.com (Iain Wacey) (05/21/91)

 I have been using ptem and ldterm to provide a terminal like
Message-ID: <4333@pluto.dss.com>
Date: 20 May 91 20:42:56 GMT
Followup-To: comp.unix.wizards
Organization: Datability Software Systems, New York, NY
Lines: 9
Xref: emory comp.unix.wizards:1912 comp.unix.programmer:2123

of some limitation of ptem. It does not handle flow control
leaving it to any lower module or driver to handle STOPI
messages from ldterm. Ptem also doesn't deal with parity. Has
anyone else run into these problems? If so how did you get around
them? Has anyone written a replacement for ptem that handles these
things. In search of a real psuedo physical terminal.

Iain Wacey
cat@pluto.dss.com

cat@pluto.dss.com (Iain Wacey) (05/21/91)

 I have been using ptem and ldterm to provide a terminal like
Message-ID: <4333@pluto.dss.com>
Date: 20 May 91 20:42:56 GMT
Followup-To: comp.unix.wizards
Organization: Datability Software Systems, New York, NY
Lines: 9

of some limitation of ptem. It does not handle flow control
leaving it to any lower module or driver to handle STOPI
messages from ldterm. Ptem also doesn't deal with parity. Has
anyone else run into these problems? If so how did you get around
them? Has anyone written a replacement for ptem that handles these
things. In search of a real psuedo physical terminal.

Iain Wacey
cat@pluto.dss.com

guy@auspex.auspex.com (Guy Harris) (05/23/91)

In article <1991May20.145454.682@arizona.edu> cat@pluto.dss.com (Iain
  Wacey) writes:

Some stuff with the first line of the message in the middle of the
headers.  You might want to fix your news software, or tell whoever
maintains it to fix it....

>of some limitation of ptem. It does not handle flow control
>leaving it to any lower module or driver to handle STOPI
>messages from ldterm.

It doesn't handle flow control coming into the pseudo-tty, no; it leaves
that up to the streams mechanism to handle, just as other pseudo-tty
mechanisms do.

>Ptem also doesn't deal with parity.

The data path that a pseudo-terminal sends its data over isn't an
asynchronous serial line, as is the case with real terminals; it's
generally called "main memory", and it often not only has parity but
ECC; why do you want "ptem" to deal with the parity or ECC on main
memory?

The same is true of the BSD pseudo-tty mechanism, BTW; has anybody
*ever* implemented a pseudo-tty mechanism that "deals with parity" in
that sense?  If so, why?

If you're ultimately connecting the process on the controller side of
the pseudo-tty to a real serial line, and want to handle parity on the
real serial line, let the hardware on the real serial line do it for
you.  If you want mode settings done on the pseudo-tty propagate through
to the real serial line, have the process on the controller side request
that M_IOCTL messages be copied to it, and have it propagate settings
done on the pseudo-tty to the serial port (although I remember hearing
from somebody that the "ioctl snooping" code has bugs in it).