Re: Serial console unusable with poky-image-sdk

[Darren Hart <dvhart@linux.intel.com>]

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.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel