Syslinux - May 2016 - syslinux vs isolinux - com32 serial port output problem

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?


--
Burt Janz
Principal Embedded Engineer
Exelis / Harris
85 Northwest Blvd.
Nashua, NH  03063
603-459-2255

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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?
> 
Be part of the community that you consult.
Subscribe to the mailinglist.

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?
> > 
> 
> Be part of the community that you consult.
> Subscribe to the mailinglist.
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.


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