On Thu, 3 Nov 2011, David Airlie wrote:

Well the current plan I had for this was to do it in userspace, I don't think the kernel
has any business doing it and I think for the simple USB case its fine but will fallover
when you get to the non-trivial cases where some sort of acceleration is required to move
pixels around. But in saying that its good you've done what something, and I'll try and spend
some time reviewing it.

The reason I opted for doing this in kernel is that I wanted to confine 
all the changes to a relatively small set of modules. At first this was a 
pragmatic approach, because I live out of the mainstream development tree 
and I didn't want to turn my life into an ethernal 
merging/conflict-resolution activity.

However, a more fundamental reason for it is that I didn't want to be tied 
to X. I deal with some userland applications (that unfortunately I can't 
provide much detail of .... yet) that live directly on the top of libdrm.

So I set myself a goal of "full application transparency". Whatever is 
thrown at me, I wanted to be able to handle without having to touch any 
piece of application or library that the application relies on.

I think I have achieved this goal and really everything I tried just 
worked out of the box (with an exception of two bug fixes to ATI DDX
and Xorg, that are bugs with or without my work).

-- Ilija