[Intel-gfx] [PATCH 10/16] drm/i915: Handle stolen objects for pread

[Chris Wilson]

On Sat, 1 Dec 2012 01:03:39 +0100, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Sat, Dec 1, 2012 at 12:46 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On Fri, 30 Nov 2012 23:33:43 +0100, Daniel Vetter <daniel at ffwll.ch> wrote:
> >> On Thu, Nov 15, 2012 at 11:32:25AM +0000, Chris Wilson wrote:
> >> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >>
> >> Tbh I don't see any reason for handling pwrite/pread support for stolen
> >> mem backed objects. I'll leave these two patches here (plus the prep one
> >> to differentiate between stolen and dma_bufs) for now until a user pops
> >
> > The problem is that constitutes a change in ABI, so I was trying to make
> > sure stolen buffer objects were first class from day one. The only
> > saving grace is that userspace can only access the stolen object for
> > fbcon, but it is still available...
> 
> Hm, I've forgotten that userspace can get at the fbcon. Does it really
> do that? The problem I see here is untested code and no sane way to
> test it.

Hint: the bogus obj->gtt_offset == 0 check was found experimentally. :)

No one pwrites/preads to the fbcon, today. If it makes you feel
any better, I would like to be able to create objects preferrentially
from stolen (e.g. scanouts) and you could build a test interface on top.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre