Hi, Dave.

I have tried the patch you attached to this bug report on 2015-09-16 on a
couple of different systems with Linux 4.3-rc2, and confirm that I have so far
not seen any DP-MST related kernel null pointer dereferences.  I do see such
oopses on Linux-4.3-rc2 without your patch.  So, I would encourage you to send
it or something similar upstream if you have not done so already.

By the way, just to warn you that not everything is perfect, I still see
apparently invalid video from one of two DP-MST hubs that I have been using
with 4.3-rc2 + your patch, but that is outside the scope of this
freedesktop.org bug report.  So, I expect to test a little more and close this
bug as "resolved" once your patch or the equivalent appears in a mainline Linux
release candidate.

Thank you very much for your help!