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Date:      Thu, 21 Sep 2006 11:09:04 -0500
From:      Dan Nelson <dnelson@allantgroup.com>
To:        Anton Shterenlikht <mexas@bristol.ac.uk>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: what happened to /dev/cuaa0
Message-ID:  <20060921160904.GB73717@dan.emsphone.com>
In-Reply-To: <20060921153727.GA20997@mech-aslap33.men.bris.ac.uk>
References:  <6.2.5.6.1.20060921193135.0308c080@singnet.com.sg> <20060921150005.GA73717@dan.emsphone.com> <20060921153727.GA20997@mech-aslap33.men.bris.ac.uk>

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In the last episode (Sep 21), Anton Shterenlikht said:
> After reading Section 22.2.2.2.2 of the Handbook my understaning is
> that the same serial port can be addressed as either /dev/ttydN or
> /dev/cuadN. Is that correct?

Yes.
 
> I'm confused by the "Call-in" - "Call-out" terminology. I have an
> external modem connected to 1st serial port, and I use it as
> /dev/ttyd0. Does it mean it becomes a call-in device?

The only real difference between the devices is that call-in devices
block when you try to open them, and unblock when carrier is detected
(i.e. if someone calls into the modem and it's set to auto-answer).
When a process is blocked, another process can "steal" the port by
opening the callout device, which doesn't block.  It's described in the
sio manpage, too.

-- 
	Dan Nelson
	dnelson@allantgroup.com



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