Syslinux - Aug 2013 - com32 module compatibility between 5.x versions

On 2013.08.10 04:07, H. Peter Anvin wrote:
>> My application already its own version of the Syslinux installer [1],
>> and simply requires the relevant ldlinux.sys file to be provided.
>
> But that, too, is version-specific.
I think there may be a misunderstanding here.

Are you saying that when installing ldlinux.sys + ldlinux.bss v5.01 on a 
FAT filesystem, the installer needs to perform something different than 
when when installing ldlinux.sys + ldlinux.bss v5.10 (outside of the 
differences prompted by the bss itself)?

So far I haven't found any major differences in the processing of these 
two files for FAT installation of Syslinux between 4.06 and 5.10, so 
that would be news to me. If there exist any differences in the steps to 
install a .sys+.bss from one version to the next, I would of course very 
much like to get an overview of what they are, so that I can update my app.

I didn't mention the bss until now, because that's a 512 bytes file and 
not much of a concern. Of course, if the idea is that we would append 
ldlinux.sys to isolinux.bin, ldlinux.bss would preferably have to be 
appended to.

Would an isolinux.bin that includes ldlinux.sys + ldlinux.bss from the 
same version as the ISO's .c32 still not be enough to get Syslinux 
installed on USB, and working with these modules?

Regards,

/Pete

On 08/10/2013 08:02 AM, Pete Batard wrote:
> On 2013.08.10 04:07, H. Peter Anvin wrote:
>>> My application already its own version of the Syslinux installer
[1],
>>> and simply requires the relevant ldlinux.sys file to be provided.
>>
>> But that, too, is version-specific.
> 
> I think there may be a misunderstanding here.
> 
> Are you saying that when installing ldlinux.sys + ldlinux.bss v5.01 on a
> FAT filesystem, the installer needs to perform something different than
> when when installing ldlinux.sys + ldlinux.bss v5.10 (outside of the
> differences prompted by the bss itself)?
> 
Potentially, yes.  I don't think 5.01 and 5.10 specifically have any
chances, but changes could be at any time.

	-hpa

On 2013.08.10 17:21, H. Peter Anvin wrote:
> Potentially, yes.
Now we're getting somewhere.
> I don't think 5.01 and 5.10 specifically have any
> chances, but changes could be at any time.
Which is fine, and pretty much what can be expected from any software at 
any time.

Regardless of whether I embed the multiple versions of ldlinux.sys/.bss 
in the app, or they come from the ISO, I will have to support any 
differences in the installation protocols anyway. And doing that is 
something that has always been on my radar as Syslinux evolves.

I was actually pleasantly surprised to find that the switch from 4.x to 
5.x required no major changes in the FAT installation method (haven't 
tried 6.x yet).

Thus, supporting 3, 4 or more wildly different installation procedures, 
that I can mostly copy from the official Syslinux/win32 source, and that 
are unlikely to result in more than a few extra KB of code, is no big 
deal, so long as I could obtain the .sys+.bss from isolinux.bin.

Especially, it is much preferable to either:
- Embed a single specific version, most likely the latest stable, with 
all possible .c32 modules, and having a single Syslinux installation 
method... but that I need to upgrade as required with each Syslinux release.
- Embed all the .sys+.bss versions from 5.00 up, so that I can support 
ISOs created with those versions, and still have to handle all the 
installation methods for these versions, if any differences exist.

All in all, the amount of work required is basically the same.

However, being able to simply fetch the relevant .sys and .bss from 
future ISOLINUX based ISOs would make a world of difference in terms of 
how large the application needs to be, or how inconvenient it becomes 
for users if requiring them to go online, to download the required 
Syslinux files.

Regards,

/Pete