Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site cmcl2.UUCP
Path: utzoo!linus!philabs!cmcl2!salkind
From: salkind@cmcl2.UUCP (Lou Salkind)
Newsgroups: net.bugs.4bsd
Subject: dh soft carrier bug
Message-ID: <1776@cmcl2.UUCP>
Date: Fri, 27-Jan-84 19:52:09 EST
Article-I.D.: cmcl2.1776
Posted: Fri Jan 27 19:52:09 1984
Date-Received: Sat, 28-Jan-84 06:04:28 EST
Organization: New York University
Lines: 24

Subject: dh soft carrier bug
Index:	sys/vaxuba/dh.c 4.2BSD

Description:
	If the soft carrier flag for a dh line is set (dhsoftCAR), and a
	dm modem interrupt occurs on the line, the TS_CARR_ON flag may be
	cleared.  This causes future reads/writes to the terminal to return
	EIO.
Repeat-By:
	On a line with modem control, bring down DTR to force a modem
	interrupt.  (This really can happen!)
Fix:
	In dmintr(), add the declaration:
		register int unit;
	and change
		if (addr->dmcsr&DM_CF) {
			tp = &dh11[(dm<<4)+(addr->dmcsr&0xf)];
	to
		unit = addr->dmcsr & 0xf;
		if (addr->dmcsr&DM_CF && (dhsoftCAR[dm]&(1<<unit)) == 0) {
			tp = &dh11[(dm<<4)+unit];
	
	(Some may rationalize that the current behavior is correct, but
	in my opinion soft carrier means "ignore modem signals.")