Comment 32 for bug 603064

I've pushed addition checks from the dri WAIT_FOR_EVENT handling as they didn't appear to negatively impact my machine:

commit 272d1c14a39c32ade39b5a8b080a891f2b3d6e8e
Author: Chris Wilson <email address hidden>
Date: Fri Jul 9 10:41:19 2010 +0100

    video: apply the crtc box checks from dri.

    The dri code is much more careful in ensuring that the scan lines that
    is waits for are valid. Copy this code to video, with a bit of work this
    can be refactored, and perhaps even teach dri how to handle rotated
    front buffers.

    References:

      Bug 28964 - [i965gm] GPU infinite MI_WAIT_FOR_EVENT while watching video
                  in Totem
      https://bugs.freedesktop.org/show_bug.cgi?id=28964

However, these are just a set of extra sanity checks. It is not clear under what circumstances the machine froze so I cannot say whether this is the fix for the bug.