Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site umcp-cs.UUCP
Path: utzoo!watmath!clyde!cbosgd!ihnp4!qantel!lll-crg!gymble!umcp-cs!chris
From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix
Subject: Re: How does litout work
Message-ID: <2360@umcp-cs.UUCP>
Date: Fri, 29-Nov-85 15:33:33 EST
Article-I.D.: umcp-cs.2360
Posted: Fri Nov 29 15:33:33 1985
Date-Received: Sat, 30-Nov-85 06:56:34 EST
References: <390@oscvax.UUCP> <170@brl-tgr.ARPA>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 54

In article <170@brl-tgr.ARPA> gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) writes:

>> I seem to recall that LITOUT was slightly buggy and you had to go
>> thru some special contortions to get it to work properly.

> The word was that LITOUT would not stick unless you set it a
> second time.

No:  The problem was that the device drivers did not call the
`param' routine when changing the local mode word.  Only TIOCSETP
and TIOCSETN would force a call.  With one of these buggy drivers,
to set LITOUT mode, use something like the routine below.

#include <ioctl.h>

/*
 * Set LITOUT mode on the tty line corresponding to the
 * descriptor `fd'.  Since you may not have installed the
 * (trivial) fix in your kernel for the bug, we use a
 * kludge.
 *
 * The fix:  In each tty device driver, find the code for
 * ioctl (e.g., `dhioctl' or `dzioctl').  There will be a
 * bit of code that looks like this:
 *
 *	if (cmd == TIOCSETP || cmd == TIOCSETN)
 *
 * Change the `if' statement to read:
 *
 *	if (cmd == TIOCSETP || cmd == TIOCSETN || cmd == TIOCLSET ||
 *	    cmd == TIOCLBIS || cmd == TIOCLBIC)
 *
 */
set_litout_with_bug_workaround(fd)
	int fd;
{
	int litout = LITOUT;
	struct sgttyb sg;

	if (ioctl(fd, TIOCLBIS, &litout))
		return (-1);	/* probably not a tty line */
	/*
	 * Here is the workaround.
	 */
	if (ioctl(fd, TIOCGETP, &sg))
		return (-1);
	if (ioctl(fd, TIOCSETP, &sg))
		return (-1);
	return (0);
}
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu