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Date:      Fri, 20 Oct 2000 13:18:38 +1000 (EST)
From:      andrew@ugh.net.au
To:        Alexander Maret <maret@atrada.net>
Cc:        "'freebsd-hackers@freebsd.org'" <freebsd-hackers@freebsd.org>
Subject:   RE: How to sense DCD on serial port?
Message-ID:  <Pine.BSF.4.21.0010201314360.68644-100000@starbug.ugh.net.au>
In-Reply-To: <58A002A02C5ED311812E0050044517F00D260A@erlangen01.atrada.de>

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On Thu, 19 Oct 2000, Alexander Maret wrote:

> DCD because this takes ernormous cpu time. Is there a possibility
> to get a signal,intr or whatever, whenever the state of DCD changes?

Umm....I'm not sure but wouldn't you get SIGHUP if DCD was dropped? It
would look like the "dialed in user" had closed the connection. Not to
sure though. I don't think you get anything when it goes high again
although a blocked open will return so you might be able to hack up
something there...but there must be a better way :-)

> If not, what could you think of I have to do to implement such
> a feature?

You could look at the source for various serial port related stuff such as
cu and tip. You may even get some hints from looking at getty etc that
handles serial logins. Perhaps the sio source might help as well.

Andrew



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