[Xorg] The big multiconsole nasty

[Adam Jackson]

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On Tuesday 06 July 2004 11:41, Matthieu Herrb wrote:
> Keith Whitwell wrote:
> > Daniel Stone wrote:
> >> In Debrix (the modular build of the X.Org server), dlloader is used
> >> everywhere, and I feel tremendously good about it.
> >
> > Hooray!
>
> Is it possible to have OS independant binary modules with this loader?

Short answer no, long answer yes.  It's tricky but not impossible.  To get a 
portable ELF module, for example, you'd need to a) only use symbols defined 
in the server (and the libraries it's linked against) or in other modules, 
and b) not rely on any OS-specific features of the linker (versioned symbols 
on Linux might be an instance of this, but are there any ELF platforms that 
don't have this?).  There might be one or two other caveats but that's all 
that springs to mind ATM.  That will get you portability among OSes with the 
same ABI and a common subset of supported binary formats.  I would expect, 
for example, that Linux-x86-ELF modules would have little trouble on 
FreeBSD-x86 (either directly or using their Linux emulation).

I would posit, however, that OS-independence in drivers is a false economy.  
OSes are cheap, get a multi-boot rig and compile them all directly.  Or use a 
cross-compiler.  From the perspective of the graphics card manufacturer, 
you'd need to have the target platform around for testing anyway if you're 
going to declare it a supported platform.

Finally, if all else fails, it may be possible to keep the old loader around 
specifically for obstreperous vendors who don't feel like adding another 
machine to the compile farm.  This would need some hacking to make work - in 
my tests the two module loaders are _not_ cross-callable - but it should be 
doable.

- - ajax
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