[ubuntu-x] Proprietary driver ABI handling

[Christopher James Halse Rogers]

On Mon, 2011-01-31 at 23:08 +0100, Alberto Milone wrote:
> On 30/01/11 23:40, Christopher James Halse Rogers wrote:
> > Hey all
> > 
> 
> Hi Chris
> 
> > As a part of the drive to Xserver 1.10, I've noticed that the fglrx and
> > nvidia proprietary drivers don't have the appropriate Depends: to
> > prevent the X server being updated from underneath them. (nvidia bug: LP
> > #616214, no existing fglrx bug)
> > 
> > A simple fix would be to add ${xviddriver:Depends} to their dependency
> > fields, which will add a dependency on the current Xserver video ABI
> > metapackage.  This is sub-optimal in two ways:
> > 1) We need to do a mock “rebuild” against each new Xserver ABI
> > 2) It makes checking Xserver bugs against older ABIs unnecessarily
> > difficult.
> > 
> 
> We already do the following:
> Provides: ${xviddriver:Provides}
> 
> and rebuild the packages when the ABI changes.
> 
> I've never thought of using ${xviddriver:Depends} and I was wondering
> what driver uses that (maybe some open driver?)
> 

${xviddriver:Depends} is the new(ish, as of ~Maverick?) Debian XSF way
of keeping the server and drivers in sync.  Rather than have the
xserver-xorg-core package declare a Breaks on all the ABIs it doesn't
support, drivers are/will be expected to declare a Depends on the ABI
they require.  All the open video drivers are (should be?) doing this
now.

It's expected that drivers will eventually stop Provide-ing
xserver-xorg-video-$ABI, and instead just Provide: xorg-driver-video.
That will be handled by the xsfbs helpers, though.

> > Since the proprietary drivers support multiple server ABIs, I suggest
> > that we keep a list of these in the packaging and add a dependency
> > satisfied by any of the appropriate xserver-xorg-video ABIs.
> > 
> > This has the advantage that the default “forgot to update” failure mode
> > is that an upgrade fails with unresolved dependencies rather than a
> > broken X, and less work at Xserver upgrade time.
> > 
> 
> Another problem is that currently, when you try to install the driver,
> you may end up removing X, which can be a problem ;)

Oooh, yeah.  A Depends: on ${xviddriver:Depends} would solve that,
too :).

> 
> > It has the disadvantage that we need to maintain a list of supported
> > ABIs, and we need to produce the dependency field outside of the xsfbs
> > helper system, so they could get out of sync.  I don't think these are
> > big disadvantages, as the supported ABI list changes approximately once
> > per cycle, and the xsfbs system changes even less often (and we'd need
> > to deliberately update when it does anyway).
> > 
> > Thoughts?
> 
> I think it's fine to do so, as (so far) I've never faced 2 ABI changes
> in the same cycle, mostly because AMD and NVIDIA wait (at least) for the
> ABI freeze before they release a driver which supports the new ABI.
> 
> Regards,
> 


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