From owner-freebsd-current@FreeBSD.ORG  Tue May 27 17:53:28 2008
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: current@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 777611065673;
	Tue, 27 May 2008 17:53:28 +0000 (UTC) (envelope-from bms@FreeBSD.org)
Received: from out1.smtp.messagingengine.com (out1.smtp.messagingengine.com
	[66.111.4.25]) by mx1.freebsd.org (Postfix) with ESMTP id 443388FC17;
	Tue, 27 May 2008 17:53:28 +0000 (UTC) (envelope-from bms@FreeBSD.org)
Received: from compute2.internal (compute2.internal [10.202.2.42])
	by out1.messagingengine.com (Postfix) with ESMTP id 7C509110064;
	Tue, 27 May 2008 13:53:27 -0400 (EDT)
Received: from heartbeat1.messagingengine.com ([10.202.2.160])
	by compute2.internal (MEProxy); Tue, 27 May 2008 13:53:27 -0400
X-Sasl-enc: FUdG9lMuSyinLn2Nqn0cQ//xZEpmPsSIQH97MabdU9Io 1211910806
Received: from empiric.lon.incunabulum.net
	(82-35-112-254.cable.ubr07.dals.blueyonder.co.uk [82.35.112.254])
	by mail.messagingengine.com (Postfix) with ESMTPSA id 0131C32E6;
	Tue, 27 May 2008 13:53:25 -0400 (EDT)
Message-ID: <483C4A94.4000107@FreeBSD.org>
Date: Tue, 27 May 2008 18:53:24 +0100
From: "Bruce M. Simpson" <bms@FreeBSD.org>
User-Agent: Thunderbird 2.0.0.14 (X11/20080514)
MIME-Version: 1.0
To: Julian Elischer <julian@elischer.org>
References: <51989.1211875439@critter.freebsd.dk>
	<483BC27C.6010102@elischer.org>
	<5229B4D7-40F0-4D45-93F1-244FA05E0304@mac.com>
	<483C49DC.3080108@elischer.org>
In-Reply-To: <483C49DC.3080108@elischer.org>
X-Enigmail-Version: 0.95.6
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Ed Schouten <ed@80386.nl>, current@FreeBSD.org,
	Marcel Moolenaar <xcllnt@mac.com>, arch@FreeBSD.org,
	Poul-Henning Kamp <phk@phk.freebsd.dk>,
	Robert Watson <rwatson@FreeBSD.org>,
	Ade Lovett <ade@FreeBSD.org>, net@FreeBSD.org
Subject: Re: HEAD UP: non-MPSAFE network drivers to be disabled
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 27 May 2008 17:53:28 -0000

Julian Elischer wrote:
>
> While this is a good idea on it's own, the difference between
> what that achieves and what a line discipline achieves is that
> a line disciplin is hardware independent and can even be used
> on a virtual device.
I was under the impression that the back-end for UART was light weight 
enough that it could be used as a virtual device.

For example: Many years ago I tried to get the WinModem working in my 
IBM ThinkPad T23. UART lends itself well to being a wrapper for the DSP 
microcode without having any of the historical tty baggage.

In the case of UART the "translation shim" moves from on top of the 
device node to underneath, in much the same way as has happened for GEOM.