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To: Fabrice Gautier <gautier@email.enst.fr>
Cc: Reto Baettig <baettig@scs.ch>,
        Linux Alpha mailing list <linux-alpha@vger.rutgers.edu>,
        Linux Kernel Mailinglist <linux-kernel@vger.kernel.org>
Subject: Re: serial console problems with 2.4.4
In-Reply-To: <3AEFD943.8FE23199@scs.ch> <20010502130958.38BB.GAUTIER@email.enst.fr>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: 02 May 2001 10:37:21 -0600
In-Reply-To: Fabrice Gautier's message of "Wed, 02 May 2001 13:15:05 +0200"
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Fabrice Gautier <gautier@email.enst.fr> writes:

> On Wed, 02 May 2001 11:54:11 +0200
> Reto Baettig <baettig@scs.ch> wrote:
> 
> > Hi
> > 
> > I just installed 2.4.4 on our alpha SMP boxes (ES40) and now I have
> > problems with the serial console:
> 
> I get same kind of problem when upgrading from 2.4.2 to 2.4.3 and using
> busybox as init/getty 
> 
> The problem was a bug in busybox. The console initialisation code was
> not correct.
> > 
> > sulogin does not accept input from the serial line
> > mingetty does not accept input from the serial line
> > agetty works fine
> 
> So this this probably a sulogin/mingetty problem. They should set the
> CREAD flag in your tty c_cflag.
> 
> the patch for busybox repalced the line
> 	tty.c_cflag |= HUPCL|CLOCAL
> by
> 	tty.c_cflag |= CREAD|HUPCL|CLOCAL
> 	
> Hope this help.

This part is correct.  

However the kernel sets CREAD by default.  
sysvinit (and possibly other inits) clears CREAD.
I wish I knew where the breakage actually occured.

And then sulogin/mingetty need to reenable it.

It's not too big of a deal except the serial code doesn't accept SAK's
when CREAD is clear.

Eric