revisiting the blacklisting of i855

[Jolan Luff]

Hi,

I ran into problems with installing Lucid on my IBM x40 due to the i855
KMS blacklisting.  I successfully used Stefan Glasenhardt's fixes listed
here:

https://wiki.ubuntu.com/X/Bugs/Lucidi8xxFreezes#GTT%20Incoherency%20Patch

to re-enable Xvideo and play games with DRI on Lucid.

I recently installed the Maverick beta and had problems with a missing
mouse cursor due to this bug:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/614176
http://bugs.freedesktop.org/show_bug.cgi?id=29413

I also had problems with GPU freezes again as expected.  I compiled a
new Maverick kernel with the GTT incoherency patch and a partial revert of
the commit that caused the missing mouse cursor.  Now I can watch videos
and play games with DRI in Maverick as well without GPU hangs.

Since I am not the only one to have reported success with these patches,
I propose reverting the i855 blacklisting:

https://lists.ubuntu.com/archives/kernel-team/2010-August/012518.html

and committing Stefan's 2.6.35 path for GTT incoherency (applies with
some fuzz):

http://glasen-hardt.de/wp-content/uploads/2010/05/fix-i8xx-gtt-cache-coherency-v9-2.6.35.1.patch

and this patch which disables a blanket application of quirks to the
i855 chipset (even when not needed) which causes the missing mouse
cursor:

http://gormsby.com/downloads/fix-i8xx-missing-mousecursor.patch

Somewhat related is that the fallback to vesa doesn't seem to work on
my laptop when the i855 blacklist is in place. Xorg simply refuses to
start.  This may be a problem with my custom kernel but I didn't see any
mention of testing the vesa fallback, just an assumption that it should
work so I thought I should mention it.

This is my first time attempting to contribute to Ubuntu so please
forgive me if I missed some steps of the process.  I'm in #ubuntu-kernel
as jolan if anyone cares to discuss this realtime.

Cheers,

- Jolan