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From: paul@unisoft.UUCP (Paul Campbell)
Newsgroups: comp.bugs.sys5
Subject: Re: CLOCAL, or catch-22
Message-ID: <523@unisoft.UUCP>
Date: Wed, 26-Aug-87 00:54:51 EDT
Article-I.D.: unisoft.523
Posted: Wed Aug 26 00:54:51 1987
Date-Received: Fri, 28-Aug-87 00:39:33 EDT
References: <325@nsta.UUCP> <25073@sun.uucp> <3607@sdcsvax.UCSD.EDU> <169@edm.UUCP> <1382@killer.UUCP> <677@stride.Stride.COM>
Reply-To: paul@unisoft.UUCP (Paul Campbell)
Organization: UniSoft Corp., Emeryville, CA
Lines: 43

In article <677@stride.Stride.COM> bruce@stride.stride.com.UUCP (Bruce Robertson) writes:
>
>What is really needed is a device driver that has two interfaces, one
>that totally ignores CD (for hardwired lines and talking to modems in
>the outgoing direction), and one that handles CD in the "normal" way
>(for dialing in).  There should also be an ioctl on the hardwired
>interface to tell it that you now want to pay attention to CD, so that
>when you lose your connection to the remote machine you aren't left
>talking to the modem, which tends to confuse naive users, and is also
>a security hole.  There would also be an interlock, so that both
>interfaces could be used at once.  This driver would make all the
>modem turnaround programs that are in abundance totally unnecessary.
>You simply put a getty on the dialup interface, which blocks waiting
>for CD, and then freely use the hardwired interface, which works since
>the dialup interface isn't completely open.  Obviously, the dialup
>interface needs to avoid waking up the getty if the hardwired
>interface causes a CD by calling a remote system.

	I don't think that this is the answer, not because it doesn't work
but because it wont work in the future. We used to use bit 8 in a minor number
for enabling carrier sleeps on open but once you start writing streams
based drivers (we have a System V streams line discipline) you can't
have multiple open devices (with DIFFERENT minor numbers) otherwise you get
two totally different stream stacks built. I guess you could do it with two
seperate drivers.

Our solution is a set of ioctls (supported by stty) that are remembered after
the tty is closed that turn on/off modem control.  Stty of course has an
option that opens a device O_NDELAY.

I think that the real answer to this problem is a smart gtty, maybe there
could be a signal that can be delivered to a terminal process group, it
would be normally ignored but gtty would catch it and give up the terminal for
a period of time??? 


	Paul 


(C) Copyright Paul Campbell, you only may redistribute if your recipients can. 
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Nothing here represent the opinion of Unisoft or any of its employees (but me).
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