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

[Good Old Idea]

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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