[Nix-dev] Dropping --with-gallium-drivers=i965 from mesa

[Mathijs Kwik]

On Sat, Jan 21, 2012 at 12:48 PM, Arie Middelkoop <amiddelk at gmail.com> wrote:
> Hi Mathijs,
>
>> But as already stated, I don't mind stuff breaking. I do mind slow
>> procedures for changes :)
>
>
> Nice that you fixed it :)
>
> So, if I understand it correctly, the intel driver/mesa/etc combination in
> nixpkgs is currently broken (it's not just my hardware). That by itself
> should be enough justification to apply your patch.

It's more subtle than that.
There's a new promising driver architecture called gallium3d. It's
meant to become platform independent (even windows) and able to
support a lot of frontends (opengl/directX) and backends (drivers).
This is still quite experimental, but shaping up ok.Currently, the
gallium3d drivers are shipped with mesa, but disabled by default
(configure option).
For owners of nvidia/ati cards however, the open source xorg drivers
don't support any 3d stuff, so the ati/nvidia gallium drivers are all
they have. They turn out to be quite good quality already because of
this, and most distributions enable them for these cards. If it
doesn't work out for certain users, they can always switch to the
available closed source drivers.
For intel cards however, the situation is different. Intel drivers
(the xf86-video-intel package) have always (or at least for a long
time now) been open source, and with good 3d/accelleration/video
support. So there's not really a need for gallium there. Of course it
would be nice in the end to have a single unified cross-platform
driver for all hardware, but we're just not there yet. Intel (the
company) doesn't support gallium. Of course all specs are open and
they provide what's needed for others to do what they want, they just
don't work on it themselves. As a result of this (normal users already
happy with current open driver, intel not contributing), development
for i915 and i965 gallium drivers has lagged a bit behind.
The i965 case got so bad that it was thrown out just after the latest
mesa release, so that option isn't even available anymore, but for
i915 I think the experience is also not on par yet with the current
driver.
I believe some developers might want to try stuff with it, but for the
"normal user" case, the intel gallium drivers should be turned off.
Other distributions seem to do this as well.

>
> Some considerations:
> a) The change to dri2proto might break other drivers. I guess we only find
> out by applying the patch and somebody complaining about it. But as far as I
> recalled, the newer dri2pro only had additional API functions, so that
> should be fine.

I agree, this commit isn't strictly needed, I just thought it would be
smart to do now, as both mesa and proto changes trigger rebuilds, so
they would be combined.

As far as I've seen, proto upgrades are quite harmless. As long as x
clients/libs use the same version as the x server, it's fine. I don't
think I've ever seen patches/fixes for proto stuff with other
distro's.

But you are right, this change _might_ disturb others, so it shouldn't
be part of the bugfix patch.

On the other hand, the intel 2.17 x driver was added to nixpkg, which
depends on this proto version (breaks build otherwise). So in a way
this is just a fix as well :)

> b) If I understand the dicussion about mesa correctly, your patch disables
> discontinued software, so that should not cause any trouble either.

Correct.

>
> I could in principle commit your patch tonight or tomorrow night so that the
> buildfarm can rebuild the packages overnight.

That's fine with me. I'm not in a hurry as my local machine already
rebuilt it all.

As long as we all agree this is just a regression fix for certain
hardware, it's ok.
The proto upgrade I'm not sure about though. I would combine the 2
just to have a single rebuild, but perhaps some more people can
input?...

>
> Cheers,
> Arie