[syslinux] garbage on serial console after pxelinux.0 is loaded

[Scheie, Peter M]

-----Original Message-----
From: hpa at zytor.com [mailto:hpa at zytor.com] 
Sent: Wednesday, April 04, 2018 4:26 PM
To: Scheie, Peter M
Subject: RE: [syslinux] garbage on serial console after pxelinux.0 is loaded

On April 4, 2018 2:08:12 PM PDT, "Scheie, Peter M" <Petre.Scheie at gd-ms.com> wrote:
>-----Original Message-----
>From: Syslinux [mailto:syslinux-bounces at zytor.com] On Behalf Of H.
>Peter Anvin via Syslinux
>Sent: Wednesday, April 04, 2018 1:54 PM
>To: syslinux at zytor.com
>Subject: Re: [syslinux] garbage on serial console after pxelinux.0 is 
>loaded
>
>On 03/05/18 12:17, Scheie, Peter M via Syslinux wrote:
>> A little more info:
>> I was mistaken in saying that the garbage on the screen doesn't
>interfere with typed commands/stanzas; it does.  If I can type the name 
>of a stanza and hit enter quickly enough before the garbage is spat to 
>the screen, it seems to start loading a kernel, but then it aborts.
>> 
>> And the garbage appears to be varying quantities of '[0n', as in
>sometimes there will be one instance of that in the string spit out, 
>and sometimes there will be a dozen, or any quantity in between.
>Sometimes it's all just blank spaces; and sometimes, as mentioned, 
>there are fragments of text that was previously displayed.
>> 
>> Any ideas as to what [0n is?  Some sort of screen formatting?
>> 
>
>Yes, that's an attribute code <ESC>[0m.  Most likely you have BIOS 
>serial redirection *and* Syslinux serial port enabled at the same time.
>
>	-hpa
>
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>Ah, yes, of course.  Disabling it in the 'default' menu file fixed the 
>issue.  Well, sort of.  The real problem is we have a few different 
>hardware platforms.  Some have a built-in DisplayPort, which we don't 
>use, while others do not.  The SERIAL setting in 'default' is for those 
>systems that don't have a DP.  Those systems with DP default to having 
>their console redirected to COM1 (ttyS0) which is what we connect to.
>But as you pointed out, having the serial port setting in both places 
>causes problems.
>
>If we take the SERIAL setting out, those machines w/o DP appear to load
>pxelinux.0 but don't display anything.  However, they still respond to 
>keyboard input, as we have stanzas in 'default' that use pxechain.com 
>to redirect them to other PXE servers.  That suggests that we could 
>have a stanza in 'default' that simply redirects to the same PXE server 
>but to a different menu file, e.g., default.serial.  Is that possible?
>
>Peter

Yes, that works. 
--

I setup a stanza that points to a submenu, i.e., a menu from a separate file, thusly:

LABEL m
MENU LABEL DisplayPort
KERNEL vesamenu.c32
APPEND dpmenu.cfg

So, when this stanza is selected, is vesamenu.c32 reloaded with new menu arguments?  dpmenu.cfg is just a copy of 'default' but without the SERIAL settings.  But when I bootup one of the machines that has DP and try to choose 'm', I get a "Initial menu has no LABEL entries" error.  The first line in 'default' is 

DEFAULT vesamenu.c32

so that's also the first line in dpmenu.cfg; is that a problem?  Is it necessary, since the 'm' stanza called vesamenu.c32 with dpmenu.cfg as an APPEND?

Petre