Re: Serial console unusable with poky-image-sdk

[Gary Thomas <gary@mlbassoc.com>]

[-- Attachment #1: Type: text/plain, Size: 2102 bytes --]

On 01/28/2011 09:51 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.
>
>> 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.

Wolfgang has it spot-on - both the console login and dbus are
fighting over the console device.

I've been using the equivalent of this patch for months and it
solves the problem just fine.  (Sorry I didn't report it, it
wasn't high on my list)

-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
------------------------------------------------------------

[-- Attachment #2: no-stdin-for-dbus.patch --]
[-- Type: text/plain, Size: 651 bytes --]

Disconnect console from dbus - otherwise, serial console is unusable
if X session is running.

diff -ur x11-common.ORIG/etc/X11/Xsession x11-common/etc/X11/Xsession
--- x11-common.ORIG/etc/X11/Xsession	2010-08-06 06:43:51.000000000 -0600
+++ x11-common/etc/X11/Xsession	2010-07-23 12:12:00.000000000 -0600
@@ -2,7 +2,7 @@
 
 if [ -x /usr/bin/dbus-launch ]; then
     # As this is the X session script, always start a new DBus session.
-    eval `dbus-launch --sh-syntax --exit-with-session`
+    eval `dbus-launch --sh-syntax --exit-with-session </dev/null`
     echo "D-BUS per-session daemon address is: $DBUS_SESSION_BUS_ADDRESS"
 fi