I made the following change to "fix" my problems with using the serial
ports. It allows one to set the process group (for SIGIO) on a
terminal if the session has no controlling terminal (like a daemon)
and the terminal is not associated with a session. (I don't believe
this breaks the posix-ness of the code).

[I hope sending diffs like this is the "right thing"]

-brad

*** tty.c.~1~   Sun Nov  7 04:39:52 1993
--- tty.c       Tue Nov 16 08:52:07 1993
***************
*** 544,550 ****
        case TIOCSPGRP: {
                register struct pgrp *pgrp = pgfind(*(int *)data);

!               if (!isctty(p, tp))
                        return (ENOTTY);
                else if (pgrp == NULL || pgrp->pg_session != p->p_session)
                        return (EPERM);
--- 544,550 ----
        case TIOCSPGRP: {
                register struct pgrp *pgrp = pgfind(*(int *)data);

!               if ((p->p_session->s_ttyvp || tp->t_session) && !isctty(p, tp))
                        return (ENOTTY);
                else if (pgrp == NULL || pgrp->pg_session != p->p_session)
                        return (EPERM);

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