[Mesa-dev] Mesa/Gallium overall design

[Jesse Barnes]

On Mon, 12 Apr 2010 09:00:57 +0200
Michel Dänzer <michel at daenzer.net> wrote:

> On Mon, 2010-04-12 at 08:00 +0200, Luca Barbieri wrote: 
> > The Intel drivers also appear to be in the same situation, with
> > classic drivers not being dropped in favor of Gallium ones, also
> > indicating possible Gallium shortcomings leading to this.
> 
> The reasons for that are mostly political rather than technical.

Sorry, couldn't resist this flamebait.

My message wrt Gallium has been consistent at least, and I know the
other Intel developers agree with me (though they may have additional
issues with some of the interfaces specifically).

Moving to Gallium would be a huge effort for us.  We've invested a lot
into the current drivers, stabilizing them, adding features, and
generally supporting them.  If we moved to Gallium, much of that effort
would be thrown away as with any large rewrite, leaving users in a
situation where the driver that worked was unsupported and the one that
was supported didn't work very well (at least for quite some time).  

Currently, the benefits of Gallium are outweighed by this
consideration, at least in my opinion.  However, Dave has been poking
us a bit about using LLVM for a sw vertex shader implementation on 945,
which Gallium would make much easier aiui, so who knows things may
change in the future.  I still worry about delivering a high quality
and supported driver to our users though.

I don't think this consideration is political, to me it's very
practical.

I really wish the move to Gallium had been a more gradual evolution of
the current code base, since it would have allowed working drivers to
take advantage of the new infrastructure over time (though not having
worked with Gallium I won't pretend to suggest how this might have
worked best). As it stands we have a lot of duplication in the 915, 965
and r300 drivers between classic Mesa and Gallium, which seems a shame.

-- 
Jesse Barnes, Intel Open Source Technology Center