[syslinux] syslinux vs isolinux - com32 serial port output problem

Geert Stappers stappers at stappers.nl
Thu May 12 10:45:08 PDT 2016

On Thu, May 12, 2016 at 06:16:46PM +0200, Good Old Idea via Syslinux wrote:
> On Thu, May 12, 2016 at 02:29:52PM +0000, Janz, Burt via Syslinux wrote:
> > I have a need to display text to COM2 before loading a kernel.
> > The easiest way to do this was to invade menu.c32 (menumain.c) and
> > add a function to send the string out to the serial port just before
> > the selected menu "label" is executed. In menumain.c, my function is
> > called just before 'if (cmdline)'.
> > 
> > 
> > The code I wrote to initialize the hardware and send individual
> > characters to COM2 works as expected when I boot from a USB drive
> > (syslinux): the text is seen on COM2.  However, when I boot from the
> > CD, I don't see any output on COM2.?
> > 
> > 
> > syslinux.cfg and isolinux.cfg are identical.  menu.c32 executes
> > properly on the CD, so I'm assuming that I have all the needed com
> > module support on the CD.
> > 
> > 
> > In both cases, the system boots up as expected.  The only difference
> > appears to be the missing output on COM2 when booting from a CD.  Yes,
> > I have tried this using different CD drives.  I have even tried this
> > on a couple of different systems (a "final ship" and an open-frame
> > "test fixture").
> > 
> > 
> > Any ideas?
> > 
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Thank you for doing so.  Welcome to this project.

Back to ideas:

Tell more about the code that was added.  How it was build.

Not that I have profound knowledge of Syslinux code base,
but thing I can tell is that sharing which function call was used,
will help.

What I guess that is wrong, is mixing modules from different builds.

Geert Stappers
Member of the usual suspects, does non-subscribe-postings-approval
Leven en laten leven

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