Re: [ros-general] why folks

[Enrico Weigelt]

* Casper Hornstrup <chorns(a)users.sourceforge.net> [2004-02-15 17:16:50 +0100]:

>   Same reason many companies don't bother to support
> Linux. Linux kernel-mode
>  APIs change very often and Linux APIs are usually not backwards compatible. 
Well,
that's one reason where it gets its performance and flexibility from. 

BTW: the APIs for things which are interesting for hardware vendors dont change
very much (normally in one major release, the things stay the same - and they
dont change in less than a year)
Binary interfaces may change several times, but it just takes a recompile to
make it work. At least you have to ship two builds, one for smp + no-smp.
Also different builds for several architectures are required.

So you want to set up a buildfarm for those different targets. Once we have
one, it doesnt really matter if we have distinctions between kernel versions.

And if you really _need_ binary compatibility, its possible to plug in an 
ABI-adaptor, which allows running third-party binary modules.
This of course, takes away all these optimizations for those modules, but
they're working.

So it doesnt need to develop a new kernel just to have a consitent driver ABI.

<snip>
>   So, if you want to support two Linux distributions
> which are compiled with 
>  different compilers, then you need to distribute two binaries of your driver. 
>  If you want to support SMP configuration (in addition to UP configuration), 
>  you need to distribute two additional binaries. 
What's the problem ? 
Some hardware vendors are already doing it. 

If you really, really want one binary module (i.e. you feel you cannot
publish sourcecode due some contracts) you can write a very small wrapper
which loads the real binary driver. This wrapper will be opensource and 
built against the current kernel.

Have a look at nvidia's binary drivers. They went this way.


cu
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