[PATCH 0/6] drm: Explicit target vblank seqno for page flips

[Michel Dänzer]

On 04.08.2016 18:51, Daniel Stone wrote:
> On 4 August 2016 at 04:39, Michel Dänzer <michel at daenzer.net> wrote:
>> Patch 6 extends the ioctl with new flags, which allow userspace to
>> explicitly specify the target vblank seqno. This can also avoid delaying
>> flips in some cases where we are already in the target vertical blank
>> period when the ioctl is called.
> 
> Is there open userspace for this?

Sure, referenced in patch 6:

https://cgit.freedesktop.org/~daenzer/xf86-video-ati/commit/?id=fc884a8af25345c32bd4104c864ecfeb9bb3db9b

https://cgit.freedesktop.org/~daenzer/xf86-video-amdgpu/commit/?id=b8631a9ba49c0d0ebe5dcd1dbfb68fcfe907296f


> What's the behaviour vs. modeset: does the modeset request block until
> the last-requested flip is complete? If so, is there some kind of upper
> bound on the number of blank periods to wait for?

Did you read the patch? :)

The only change compared to the existing ioctl is that userspace can ask
for a flip to take effect in the current vblank seqno. The code added by
the patch checks for target vblank seqno > current vblank seqno + 1 and
returns -EINVAL in that case. This is also documented in drm_mode.h.


> Is all this tested somewhere?

Yes, I've been using it for a while on all my machines.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer