linux-kernel - Re: should RTS init in serial core be tied to CRTSCTS

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Message-ID: <m3r6rz3chb.fsf@maximus.localdomain>
Date:	Thu, 08 Mar 2007 17:51:28 +0100
From:	Krzysztof Halasa <khc@...waw.pl>
To:	Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@....net>
Cc:	Robin Getz <rgetz@...ckfin.uclinux.org>,
	Oleksiy Kebkal <kebkal@...il.com>,
	Mike Frysinger <vapier.adi@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: should RTS init in serial core be tied to CRTSCTS

Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@....net> writes:

> Unless you want two machines to monitor each other via serial console and
> each of them has only one serial port. It's not perfect, but it works well
> enough despite all claims to the contrary.

Sure, if you don't need "input" (only "console logger" function and
not "initial input/output terminal"). It has nothing to do with the
RTS "problem", though.

BTW: reasonably working, standard-compliant USB-RS232 converters
cost $15 or so. Unfortunately not that all machines have USB ports.

I agree with Russell - mixing kernel console and application's
port is asking for trouble.

OTOH I wonder what does the device in question require WRT the
serial port and WRT RTS line in particular.
I know there are some half-duplex converters which drive RTS only
while sending and which require CTS to send. They are perhaps a bit
broken and require some CSMA-alike retransmissions etc.

I don't know if one can expect RTS to stay low all the time. Even
a simple /sbin/setserial from /etc/rc.* would drive it high for
a moment. I'm afraid the only way which makes sense may be using
a customized plug.
-- 
Krzysztof Halasa
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