Friday, 5 March 2010

Lucid DRM Update

After much discussion within the Ubuntu Kernel team, the Ubuntu X team,
and with the various Graphics upstreams it has become clear that the
2.6.32 drm stack is not of sufficient quality to form a good basis for a
LTS release.  2.6.32 does not contain Nouveau so we are already committed
to a backport of that for KMS there.  Upstream is essentially saying
ATI Radeon KMS support in 2.6.32 is so bad that the recommendation is to
disable it globally.  Finally i915 does not support the latest chipsets
well, and backports are already extremely painful; chipsets which are
slated to become prevalent over the next few months.

The recommendation from upstream is to use the 2.6.33 drm stack if we
desire KMS to be enabled generally, a clear goal for Lucid.  Following a
review it does appear that the drm subsystem is sufficiently self contained
that it is possible to backport just that subsystem into our 2.6.32 tree.
This gives us a hybrid kernel gaining the long-term stable support backing
for the main kernel (a major bonus as this has to be supported for 5
years on servers) while gaining the more stable 2.6.33 graphics support
for desktop use.  Additionally upstream is essentially rejecting 2.6.32
as a supportable stack, and is committing to longer support for 2.6.33
as their stable version.  We are therefore planning to upload a hybrid
2.6.32 kernel containing the 2.6.33 drm backported.

From an Ubuntu stable maintenance standpoint we should be able to track a
hybrid of 2.6.33.y for drm and 2.6.32.y for the remainder of the kernel and
due to the separation that drm enjoys we hope to avoid major conflicts.
Plug gaining the longest possible support from upstream for each part.
This will also remove the requirement to install an LBM package to get
Nouveau cleaning up the install significantly.  It seems likely that
Debian and other distros will be following a similar hybrid approach
allowing us to share the maintenance burden.

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