[PATCH xserver] prime: clean up slave bo properly. (v2)

[Julien Cristau]

On Fri, Apr 29, 2016 at 15:54:28 +1000, Dave Airlie wrote:

> This is an ABI break, in that we now pass NULL to a function
> that hasn't accepted it before.
> 
> Alex Goins had a different patch for this but it wasn't symmetrical,
> it freed something in a very different place than it allocated it,
> this attempts to retain symmetry in the releasing of the backing bo.
> 
> v2: use a new toplevel API, though it still passes NULL to something
> that wasn't expecting it.
> 
> Signed-off-by: Dave Airlie <airlied at redhat.com>

AIUI you're assuming the handle will never be 0, even though that's a
valid fd.  Are we somehow sure that'll never happen?

Cheers,
Julien