Xserver driver merging pros & cons

[Bryce Harrington]

On Thu, Sep 15, 2011 at 01:30:02PM -0700, Chase Douglas wrote:
> Note that I'm speaking here with my personal developer hat on. Bryce
> Harrington and Chris Halse Rogers would be better to chime in on
> Canonical support for Ubuntu, but I imagine that it really doesn't
> matter too much to us because we tend to stay near the bleeding edge.

So, my perspective doing the Ubuntu xorg support for -intel, -nouveau,
and -ati is that since KMS was introduced, the _DDX_ drivers have become
a lot less important.  Pre-KMS, a lot of bug fixes required a DDX patch;
new hardware support always involved a DDX change; most new features
included significant DDX modifications.  Post-KMS, by far (>90%) of bug
fixes we see involve a kernel or mesa patch - DDX patches for bug fixes
are quite uncommon now.  Video playback and 2D acceleration still
requires DDX, but both seem to not to have nearly as much churn in
practice.

Like Chase says, I don't think it really matters too much to us.  If
we're going to backport DDX changes to a prior release we're either
going to cherrypick specific patches, or backport the entire stack.  I
don't see us needing or wanting to backport just the DDX.  It's the
kernel and mesa that matter.  So, I favor just doing whatever the
upstream developers feel is best for their own needs.

> Personally, I would prefer a monolithic tree with separate branches for
> backporting driver changes to older server versions. I would also prefer
> each driver having a stated policy of how many back revisions of servers
> are supported by upstream X.org. This would allow the distros to stay on
> a given server branch, still receive upstream driver updates, and ensure
> there is an understanding of the level of support for each individual
> driver. Also, it would keep each branch clean of the server abi #ifdefs
> and whatnot, including in back server branches.

This sounds like a good approach to me as well.  Although like I
mentioned, I really don't think the DDX's matter as discrete driver
packages that much anymore.

Bryce