linux-kernel - Re: [PATCH v1] 8250: add support for DTR/DSR hardware flow control

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Message-Id: <200808071032.16709.laurentp@cse-semaphore.com>
Date:	Thu, 7 Aug 2008 10:32:14 +0200
From:	Laurent Pinchart <laurentp@...-semaphore.com>
To:	Aristeu Rozanski <arozansk@...hat.com>
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] 8250: add support for DTR/DSR hardware flow control

Hi,

On Wednesday 06 August 2008, Aristeu Rozanski wrote:
> This patch adds support for DTR/DSR hardware flow control on 8250 driver on
> x86 machines. It's done by adding a CDTRDSR flag to work just like CRTSCTS,
> which is not done on other architectures on purpose (so each maintainer can
> allocate it). 

It's funny, serial flow control hasn't been discussed for a long time, and you're the third person to start a flow control related thread on this mailing list in a few days.

> This patch was tested with success with a serial printer configured with a
> small buffer and DTR/DSR flow control.
> 
> This is based on the work of Michael Westermann
> (http://lkml.org/lkml/2007/8/31/133) 
> 
> Comments more than welcome.

Please read the '[PATCH/RFC] 8250: Auto RS485 direction control' thread for background information. In a nutshell we need more than just CTS/RTS and DTR/DSR, and we don't have enough c_cflags bits. We will probably have to create a new ioctl.

Best regards,

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
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