[PATCH 1/2] drm: Add DRM_CAP_PRIME_SCANOUT.

[Daniel Vetter]

On Tue, Apr 4, 2017 at 12:43 PM, Lucas Stach <l.stach at pengutronix.de> wrote:
>> If I could guarantee that I'd only ever run on 4.13-or-later kernels
>> (I think that's when the previous patches will land?), then this would
>> indeed be mostly unnecessary. It would save me a bunch of addfb calls
>> that would predictably fail, but they're cheap.
>
> I don't think we ever had caps for "things are working now, as they are
> supposed to". i915 wasn't properly synchronizing on foreign fences for a
> long time, yet we didn't gain a cap for "cross device sync works now".
>
> If your distro use-case relies on those things working it's probably
> best to just backport the relevant fixes.

The even better solution for this is to push the backports through
upstream -stable kernels. This stuff here is simple enough that we can
do it. Same could have been done for the fairly minimal fencing fixes
for i915 (at least some of them, the ones in the page-flip).

Otherwise we'll end up with tons IM_NOT_BUGGY and
IM_SLIGHTLY_LESS_BUGGY and IM_NOT_BUGGY_EXCEPT_THIS_BOTCHED_BACKPORT
flags where no one at all knows what they mean, usage between
different drivers and different userspace is entirely inconsistent and
they just all add to the confusion. They're just bugs, lets treat them
like that.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch