[Fedora-packaging] Re: atrpms kernel modules

[Axel Thimm]

On Sat, Jul 22, 2006 at 09:45:51AM -0400, Jesse Keating wrote:
> On Friday 21 July 2006 14:35, Axel Thimm wrote:
> > I really thing there is a flaw and the uname-r-in-name is the only way
> > out, and I'd try to persuade people about that. Maybe they could be
> > poited to this mail thread as well, as everything is in principle layed
> > out here.
> 
> With the kabi stuff coming along, there is no longer a need to lock a given 
> module to a given kernel version, just an ABI version.  The kernel could 
> easily be bumped a version but the ABI that a particular module needs would 
> remain unchanged, and thus the module will continue to work.  Locking to a 
> uname will be pointless at this point.
> 
> Jon Masters is giving (gave?) a talk about this at OLS and was discussing 
> these things at the kernel summit I do believe.  I strongly feel we wait for 
> him to return from OLS so that we can include him in the discussion 
> surrounding packaging of external kernel modules.
> 
> As it stands, the development kernel does automatically provide an ABI 
> checksum for each module subdirectory, and rpm knows about it.  Requires on 
> an ABI supposedly works today.

kABI will not really help, as it only measures what has changed in the
ABI from on kernel release to the next, checking to see whether an old
kernel module can be safely recycled. It will not magically force
kernel developers to introduce a stable ABI, function signatures and
other symbols will change just as frequent.

And the areas where kABI would help is where the kernel has reached
some level of maturity where indeed the ABI has become stable. But
these are not the typical subsystems external kernel modules are built
for.

Currenlty the most frequent cases of kernel modules are such usually
requiring v4l2, ieee82011 or vm subsystems. And these are currently
guaranteed to change from kernel release to kernel release. And once
these stabilize and other areas of the kernel become interesting
you'll have the same situation there. Currently (the last 1-2 years)
every kernel release breaks 70-80% of external kernel modules at build
level already, and kABI would only confirm this.

So what is really needed is a kernel developers' committment to
stabilize the kernel ABI, and we are really far away from such a point
in time. And even if that were tomorrow, we need to consider legacy
support for a couple of FC releases and also RHEL for a couple of
years more.

But kABI is definitely the way towards a stable kernel ABI, just not
within the timeframe we are interested in, e.g. <= 2 years.

So for the current discussion this won't help us further.
-- 
Axel.Thimm at ATrpms.net
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