Re: about serial console problem

From: Robert J.Dunlop (
Date: Tue Jul 24 2001 - 17:29:09 EST


On Tue, Jul 24, Eric W. Biederman wrote:
> Barry Wu <> writes:
> > I am porting linux 2.4.3 to our mipsel evaluation
> > board. Now I meet a problem. Because I use edown
> > to download the linux kernel to evaluation board.
> > I update the serial baud rate to 115200.
> > I use serial 0 as our console, and I can use
> > printk to print debug messages on serial port.
> > But after kernel call /sbin/init, I can not
> > see "INIT ... ..." messages on serial port.
> > I suppose perhaps I make some mistakes. But when
> > I use 2.2.12 kernel, it ok.
> > If someone knows, please help me. Thanks!
> It's a bug in init. INIT clears the CREAD flag which means all reads
> to the console will be dropped. Why it /sbin/init works before 2.4.3
> is a mystery.

Perhaps because most of the serial drivers didn't implement CREAD (or
rather !CREAD) until then. Actually more and more have been implementing
it as we go through 2.4.x, depends when your particular driver got caught.

        Bob Dunlop                      FarSite Communications  
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