Re: Serial console unusable with poky-image-sdk

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Fri, 2011-01-28 at 09:16 -0800, Darren Hart wrote:
> On 01/28/2011 08:51 AM, Wolfgang Denk wrote:
> > Dear Darren Hart,
> >
> > In message<4D42F269.1080005@linux.intel.com>  you wrote:
> >>
> >> The serial console would show all the output of the boot process and
> >> then present a getty. It would accept my login and my password, but as
> >> soon as I was logged in, things went weird. Only every Nth character I
> >> typed made it to the console, where N was somewhere between 2 and 30.
> >
> > Indeed. And the reason for this behaviour is that you have two
> > processes reading from the console, so it depends on the scheduling
> > which of hem receives which characters.
> >
> >> I believe this had something to do with the automatic consoles the
> >> kernel will setup based on the console= parameters. By default, the last
> >
> > No, it does not.  You can test it by shutting down X11 (try:
> > "/etc/init.d/xserver-nodm stop"); this will also terminate the
> > dbus-launch process, and your login shell immediately works fine.
> >
> > Or try out the patch I posted.
> 
> 
> I'm not running X11, this is just a poky-image-minimal.
> 
> 
> >
> >> What I haven't been able to explain yet is why just omitting the getty
> >> from the tty doesn't result in console on the serial port due to the
> >> kernel's automatic console thing. So clearly there are some gaps in my
> >> explanation here, but please try this approach and let me know what your
> >> results are. Based on that, we can dig a bit more and figure out how to
> >> best setup the console= directives on the default images.
> >
> > THere is no problem with the console= settings.  It's two processes
> > reading from a single input stream. This can never work.  Try it ut if
> > you don't believe me.
> 
> Agreed on the two processes thing, that's clear. I believe the console= 
> settings impact which processes are started and which read from which 
> console devices.
> 
> And again, I can't try your patch, because I'm not running X.
> 
> Perhaps we are seeing similar problems caused by different things.

Regardless, I think we should take the patch since we have at least two
users seeing issues due to it.

Saul or I will ensure it gets in, I keep meaning to merge it but then
get distracted...

Cheers,

Richard