[Nouveau] Introduction and discussion - Nouveau for Ubuntu Lucid

[Pekka Paalanen]

Steve,

we appreciate you came forward beforehand. Below are some comments
on how I personally view the situation with Nouveau, and I believe
they are mostly the concensus among the developers.

On Sat, 21 Nov 2009 21:33:33 -0600
Steve Conklin <steve.conklin at canonical.com> wrote:

>   I'm the Ubuntu kernel team member focusing on graphics during
> the Ubuntu Lucid Lynx (10.4) cycle. At the Ubuntu developer
> summit last week, we made the decision to include Nouveau in the
> Lucid kernel.  I'd like to open a few topics for discussion with
> the Nouveau community:
> 
> First, I want to make sure we're pulling from the repo you prefer
> for delivery with the distro. I've seen the information here -
> http://nouveau.freedesktop.org/wiki/FrontPage#Source and here -
> http://lists.freedesktop.org/archives/nouveau/2009-March/002765.html
> 
> and I haven't been able to find a tree that's indicated for
> release to upstream or distros. Is the master branch on the
> freedesktop repo the best place to pull from?

That is because there are no trees for upstream nor distros yet.
The kernel upstreaming tree has not been created yet, and we are
still not sure how the development process will look like.
Whatever distros do, they are on their own. You can follow
http://nouveau.freedesktop.org/wiki/InstallNouveau , the install
guides tell which trees to use. They are basically 'master' of
nouveau/linux-2.6, libdrm and xf86-video-nouveau.

On the DRM kernel modules side, we have an issue with the ctxprogs,
previously known as voodoo: we do not know if it can be distributed
legally as is, so we are trying to play it safe. People are working
on that, and that is the major reason why Nouveau is not in staging
yet. ( http://lwn.net/Articles/357805/ )

Note, that we prefer to have the whole set of DRM kernel modules
installed from the Nouveau kernel tree, and that may sometimes
cause problems if you try to support other drivers at the same time.

On the libdrm side, even though Nouveau code is in master and
included in release packages, Nouveau is not released yet. This
means that we rely on git revisions. Releases of libdrm may
be too old for the other parts to work.

There's nothing special about the DDX, it lives in its own repo,
unreleased.

Nouveau has had the policy, that people should not try the Mesa
accelerated 3D driver, and I guess this still holds, so I would
advice against distributing that. It is still far too unstable to
be installed system-wide.

> Second, I expect that we'll have one or two calls for testing. I
> welcome discussions about any particular functionality or
> hardware that the Nouveau community would like testing coverage
> on, and any preferred tools for testing. Ubuntu testing results
> and bugs are open, and there are some tagging and processing
> tools that I can use to help get these back to the Nouveau
> community in ways that will be helpful.

The individual developers should comment on this, since I have not
written any considerable pieces of code. The wiki front page has
the generic testing request.

> Third, we have a good facility to capture logs and useful
> information after oopses, crashes, and when bugs are filed. If
> there's any information that's useful to the Nouveau developers
> that's not part of the normal kernel logs, I'll make sure we
> gather them - just let me know what you need.

Kernel and X logs are the most important to start with. Other
things that may be requested when working on a specific bug are:
- video bios dump
- kernel log with special debugging options for the DRM modules
- mmiotrace of the proprietary driver
And of course, requests to try patches or the latest git revision.

> Last, what else have I missed that I should know about?

Go for KMS, user mode setting is not that interesting.

I should probably roughly sketch the Nouveau release steps:
1. get Nouveau DRM module into staging
2. get Nouveau DRM module released in mainline kernel
3. release libdrm
4. release DDX
The timetable is completely open, so do not expect anything.

How do you plan to distribute Nouveau? Have one or two snapshots
for testing and then freezing the packages? Or do you intend to
do snapshots every once in a while to update it?

Outdated distribution packages are a bit of a pain already,
but if Ubuntu actively takes the support burden, I guess we can
live with that. It is far too tempting to say "please try the
latest git revision" before taking any deeper look into a bug
report.

Oh, could you make mmiotrace easily available on Ubuntu?
I'm not sure what your current situation is, but if it requires
a kernel recompile, it is a big step. It needs to be enabled in
the kernel configuration, and it is supposed to have
negligible impact on the system while not activated at runtime.
AFAIK, the extra memory burden is one page per cpu, plus there
can be some spurious kernel messages while using gdb.
http://nouveau.freedesktop.org/wiki/MmioTrace

It would also help if you have an easy way to switch between the
Nvidia proprietary driver and Nouveau.

-- 
Pekka Paalanen
http://www.iki.fi/pq/