Re: serial console problems with 2.4.4

From: Eric W. Biederman (ebiederm@xmission.com)
Date: Wed May 02 2001 - 11:37:21 EST


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
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