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

Ady ady-sf at hotmail.com
Fri May 13 06:22:30 PDT 2016

> On Thu, May 12, 2016 at 2:14 PM, Janz, Burt via Syslinux
> <syslinux at zytor.com> wrote:
> > Hi Geert,
> >
> > I'm building syslinux 6.04 from scratch to prevent any issues with mismatched com32 modules.  This gives me a "pure" set of modules as well as "pure" isolinux and syslinux cores.
> 6.04 hasn't seen a full release, only the pre1 pre-release.
FWIW, IMHO 6.04-pre1 is not worth much.

Actually, unless there is official pre-release(s), we should avoid 
referencing to anything as "6.04" until its final official release, and 
instead point to specific branches and commits.

> > menu.c32 works perfectly on both the USB and CD boot media: I can move around the menu and select the command that I wish to use.  In all cases, both the USB and CD boot properly into the Linux kernel.  I cannot plug both a USB and CD into this system at the same time, so I'm quite sure that I'm booting from the correct media.  For that matter, the BIOS even says "Boot from CD" and displays the isolinux-debug.bin messages before the menu appears - but only when booting from CD.
> I'm guessing physically the machine has 1 USB port and you're using a
> USB-CD drive.  This shouldn't be an issue but may be suspect.  Tried
> any machines with an IDE/SATA CD drive?  Considered modifying
> linux.c32 instead and calling it?  This would allow you to test
> without ever loading menu.c32
> isolinux-debug.bin is for debugging the loading of isolinux.bin, not
> items later in the boot process like ldlinux.c32, the config or
> menu.c32.
> -- 
> -Gene
Since I am not a developer, I am not sure I understood what "display 
text to COM2" means. I do not understand what exactly is that is being 
displayed (or at least, attempted to) either.

If we are talking about some "fixed" text, the SAY directive is one 

If each menu entry has to have a different "fixed" text being sent to 
the (serial) console, then combining CONFIG with SAY might also be an 
option. Each individual cfg (each one loaded by means of CONFIG 
directives in the main menu) would contain only one (menu) entry with 
its corresponding SAY directive.

I don't have enough experience with MENU HELP - ENDTEXT in serial 
console for me to know whether it would serve this case.

Another way to display text is by means of the DISPLAY directive, with 
a msg file containing the text and ASCII 20 / 21 / 22 / 23.

We also have the SYSAPPEND directive, in case the text is related to 
the specific hardware.

These might be alternatives. But, since I am not sure about the exact 
meaning of "display text to COM32" and what exactly is the content 
being displayed, I don't really know how far these alternatives are 
from the actual purpose.

Regarding SYSLINUX vs. ISOLINUX, perhaps the matter is related to the 
filesystem, considering that ISO9660 is read-only. Even editing an ISO 
image (without expanding its content and rebuilding it after the 
edition) is tricky and limited.

In my ignorance, I would tend to think that sharing more specific and 
accurate info, and even perhaps the patched code, _might_ help narrow 
down the problem.


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