(In reply to bmilreu from comment #65)
> Is there an easy way to backport this to 4.19 mainline? Would be very useful
> to integrate the fix into stable kernels.
> 
> As it is currently it wont work on 4.19 because it uses
> <drm/drm_atomic_uapi.h> which isnt mainlined yet. Brandon's hack works on
> 4.19 just in case it matters.
Just remove the header include. There was some refactoring, and the functions
needed in that file are in the others included.

> Last question, is this patch https://patchwork.freedesktop.org/patch/263412/
> you just submitted related to this issue? 
Looks like it's related. Thanks for taking on our issue, Nicholas.