OCD programmers and backwards compatibility :-).

Les Mikesell lesmikesell at gmail.com
Mon Jan 29 04:16:16 UTC 2007


Dave Jones wrote:

>  > So does that mean that maintaining compatibility with anything outside 
>  > that kernel developers' direct control is hopeless?  Should anyone who 
>  > cares about that just switch to Solaris now?
> 
> If you care about a kernel symbol remaining constant forever,
> then you're in for disappointment. 

What I care about is the ability for independent third parties to 
provide additional drivers that have a reasonable lifespan. And yes I am 
disappointed that the kernel developers refuse to cooperate by providing 
a stable interface.

> We do offer _some_ ABI guarantees
> with RHEL releases, but it's a ton of work to do so (even just a subset).
> Doing that for Fedora would require a lot of manpower which doesn't
> exist today. It also requires sacrificing certain upstream changes entirely,
> which makes for real pain when subsequent must-have fixes are implemented
> on top.

Yes, obviously any commercial offering is going recognize the customers' 
needs and meet them or they won't have any customers.  Unfortunately, 
free projects don't have to care - they can break vmware, ati, nvidia, 
etc's added value on whim.  Why should they worry about the effect on 
end users?

> This isn't about control, it's about long term maintainence.

No, forcing one team to do everything is not the way to do maintenance 
in a way that scales or is even itself maintainable.

> If Linux had a stable in-kernel ABI, it would be a horrific mess
> to work on, and certain problems would just be completely unfixable
> in a clean manner.

Odd, then, that more popular operating systems have managed it in a way 
that permits third party drivers for a vast variety of devices to work 
unchanged for years.

> If you want to see some of the horror show that proves this, take
> a look at what happens to a RHEL release near end of life.
> By that point, large parts of it have deviated from anything that
> ever looked like upstream, because instead of taking upstream fixes,
> we've had to bend-to-fit fixes to work around ABI constraints.

It's not having an ABI that causes this problem.  It is the fact that 
the current kernel hasn't respected it.

> Thankfully, no RHEL release lasts forever.

Don't say that... Most of my machines are running Centos 3.x.


-- 
   Les Mikesell
    lesmikesell at gmail.com




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