Subject: Re: [PATCH RFC] [1/9] Core module symbol namespaces code and intro.

From: Andi Kleen <[email-masked]>
Date: Tue, 27 Nov 2007 10:02:22 +0100

> > Perhaps you've got lots of patches were people are using internal APIs they 
> > shouldn't?
> > 
> 
> Maybe the issue is "who can tell" since what is external and what is
> internal is not explicitly defined?

Exactly.  Or rather it is not defined on the module level. We got 
"static" of course, but I think we should have a similar mechanism
on a module level.

> Explicitly documenting what comprises the kernel API (external,
> supported) 

It would not be fully supported either -- can still change etc. --
but there is a reasonable expectation that those external
APIs will change less often than internal interfaces.

> - forcing developers to identify their exports as part of the
> implementation or as part of the kernel API

That is EXPORT_SYMBOL already. The trouble is just that it covers
too much. My patchkit is trying to limit it again for a specific
use case -- exporting an "internal" interface to another module.
Or rather a set of modules. 

Standard example is TCP: TCP exports nearly everything and the
single user is the TCP code in ipv6.ko. Instead those symbols should
be limited to be only accessable to ipv6.ko. 

The reason I went with the more generic namespace mechanism
instead of EXPORT_SYMBOL_TO() is that ipv6 is ever split up
it would still work. 

Also using namespaces doesn't have any more overhead than
EXPORT_SYMBOL_TO() and the complexity is about the same
(not very much anyways -- just look at the patches) 

> - making it easier for reviewers to identify when developers are adding
> to the kernel API and thereby focusing the appropriate level of review
> to the new function

That is another reason.
 
-ANdi