Ultrix 3.1C uucp will not dial a LAT terminal modem

[Ian! D. Allen [CGL]]

I have a host-initiated LAT tty pointing at a DS200/MC port.  I thought
I'd check to see that the Ultrix 3.1C kernel knows how to deal with modem
control on LAT tty lines.  I configure /dev/tty55 using

    lcp -h /dev/tty55:CGLDSB:PORT_3

I verify that I can "tip" to it (not using /etc/acucap, though) and talk
to my modem.  No problem.  I then run this:

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/file.h>

main()
{
	int r;
	static int yes = 1;
	static int no = 0;

	int u = open("/dev/tty55", O_RDWR|O_NDELAY, 0);

	if( u < 0 ){
		perror("/dev/tty55 open");
	}

	r = ioctl(u, TIOCMODEM, &yes);
	if( r < 0 ){
		perror("/dev/tty55 TIOCMODEM");
	}

	r = ioctl(u, TIOCCAR, &yes);
	if( r < 0 ){
		perror("/dev/tty55 TIOCCAR");
	}

	alarm(60);
	r = ioctl(u, TIOCWONLINE, &yes);
	if( r < 0 ){
		perror("/dev/tty55 TIOCWONLINE");
	}
	alarm(0);

	exit(0);
}

I run the above program and get this:

    /dev/tty55 TIOCMODEM: Not a typewriter
    /dev/tty55 TIOCWONLINE: Not a typewriter

So much for that.  Looks like LAT ttys are not full ttys.  I wish it said
this somewhere in the documentation, so I didn't have to waste all this
time trying to use them.  Uucp and tip use the TIOCWONLINE ioctl via the
aculib code to wait for carrier, and since they don't check the return
code from the ioctl, it appears to "succeed", only to have it fail
immediately because no "CONNECT" string is found.

Please, people, check the return codes of your system calls!

I think I finally have to admit defeat and move my uucp call-out modem
off my DS200/MC onto a MVII serial card.  Does Ultrix 4.0 support real
modem signals on host-initiated LAT connections?  (Oh please?)
-- 
-IAN! (Ian! D. Allen) idallen at watcgl.uwaterloo.ca idallen at watcgl.waterloo.edu
 [129.97.128.64]  Computer Graphics Lab/University of Waterloo/Ontario/Canada