[syslinux] syslinux efi configuration file name proposal

[Prof. Dipl.-Ing. Klaus Knopper]

Hello Ady & list,

On Wed, Aug 27, 2014 at 08:17:51AM +0300, Ady wrote:
> > Hello Ady,
> > 
> > On Fri, Aug 01, 2014 at 08:35:27PM +0300, Ady wrote:
> > > Goal: To have one USB drive capable of booting UEFI IA32 and UEFI X64 
> > > (with an optional Syslinux menu containing multiple entries).
> > > 
> > > Problem (solved) #1: The default directory location for both 
> > > syslinux.efi is the same.
> > > 
> > > Solution #1: Rename each syslinux.efi to bootx64.efi and to 
> > > bootia32.efi.
> > > 
> > > Problem (solved) #2: Each syslinux.efi needs at least its respective 
> > > ldlinux module.
> > > 
> > > Solution #2: Each ldlinux module is renamed with its corresponding 
> > > file name extension according to firmware/architecture. Each 
> > > syslinux.efi searches for its respective ldlinux.{e32,e64} module.
> > > 
> > > Problem (solved) #3: Similarly to the ldlinux module, the other 
> > > modules also use the same file names for every firmware/architecture.
> > > 
> > > Solution #3: Use the PATH directive and a combination of relative and 
> > > absolute path notation. This solution allows maintaining current 
> > > configurations, tutorials, easy copying, in-common cfg files... as 
> > > the same "c32" file name extension is kept for all alternatives.
> > > 
> > > 
> > > Problem #4: The initial configuration file, "syslinux.cfg", is also 
> > > using the same default file name and the same default location. The 
> > > content of "syslinux.cfg" might not be in-common to both UEFI 
> > > architectures (e.g. different values for the PATH directive).
> > > 
> > >  ---- 
> > > 
> > > Proposing a solution for Problem #4: syslinux.efi should look first 
> > > for a corresponding "sysl<arch>.cfg", and then fallback to 
> > > syslinux.cfg in the same searched-for location.
> > 
> > [...]
> > 
> > Your suggested proposal is, entirely by chance, almost exactly the same
> > solution that I'm currently using in Knoppix since version 7.2, i.e.
> > bitness-dependent ldlinux.e32/ldlinux.e64 and also a
> > syslnx32.cfg/syslnx64.cfg with a fallback to syslinux.cfg. It's merely
> > renaming and adding file names to the syslinux configuration file array,
> > just a few lines of code. So far, the patch is only included on Knoppix,
> > but feel free to use it on your distro as well.
> > 
> > I'd vote for acceptance of your proposal.
> > 
> > Regards
> > -Klaus
> > 
> 
> Hello Klaus,
> 
> Is there any chance to see your customized Syslinux 6.xx source code 
> / patch(es) / commits or alike? Is there any public URL?

Apparently, the rename of ldlinux.e32 to ldlinux.e64 for the 64bit
variant is already in the mainline git, so the only change left for
automatically chosing a different config file is the tiny patch attached
here, which will

- prepend syslnx64.cfg to the config file search path for the 64bit variant
- prepend syslnx32.cfg to the config file search path for the 32bit variant
- add /boot/isolinux and /isolinux plus isolinux.cfg to the search path for
  all variants, just for the case that the "rename" was forgotten when copying
  over the files from an iso9660 CD/DVD to FAT32 flash disk.

Regards
-Klaus
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