Xserver driver merging pros & cons

[Jesse Barnes]

At XDC this week we discussed merging drivers back into the server
tree.  One thing I found frustrating about the discussion was that we
didn't have a whiteboard nor a list of the pros & cons of such a
change.  So I'd like to capture that here (from memory) to let us
continue the discussion about whether it's worth it or not.

Luc, I think you're the most vocal opponent of this move, so I've cc'd
you so you can enumerate any issues I've forgotten.

Anyway, as I recall, the issues are as follows:

Pros:
  1) easier to propagate API changes across drivers (just like Linux)
     1a) thus easier to change ABI
  2) developers focused on driver development now have more incentive
     to make sure the server works well so regular releases can still
     happen (i.e. more people working on blockers whether driver or not
     as releases approach)
  3) allows removal of driver compat code for various server versions
     3a) thus removes combinations of driver+server that developers
         have to support & test
  4) increased test coverage for the server as users wanting current
     driver code will be building new servers too

Cons:
  1) more work for distros to backport just driver changes to old
     servers (especially if people follow through on (3) above)
     1a) if backporting is harder, new hardware support will be more
         difficult to land in "enterprise" level distros
  2) harder for users to just upgrade drivers independently, now
     they'll have to build the whole server
     2a) thus less testing of current driver code from technical users

I've already made my views pretty clear; I'd prefer merging the drivers
back in.  But I don't do as much work on the DIX or DDX as I used to,
and lots of others would be affected as well, so I'd like to hear what
people think.  Have I captured the pros & cons fully?  What to distro
maintainers think?  And driver developers, both input & output?

Thanks,
Jesse