[PATCH weston 1/1] compositor: Abort on bad page flip timestamps

[Michel Dänzer]

On 06.11.2014 03:06, Frederic Plourde wrote:
> Many features, like animations, hardly depend on page flip timestamps
> to work properly, but some DRM drivers do not correctly support page flip
> timestamps (or not at all) and in that case, things start to go wrong.
>
> This patch adds sanity check to weston_output_finish_frame. By solely
> verifying that page flip timestamps are monotonically increasing, we
> make sure that :
>
> 1) Underlying driver is not throwing zeroed-out timestamp series at us.
> 2) We have not mistakenly jumped backwards because of integer overflow.
>
> If a pathological case is detected, we gracefully exit Weston
> with an appropriate exit code to help developers debug their drivers.

That seems a bit harsh. IIRC, zero can be returned for the timestamp 
intermittently if no accurate timestamp value can be determined, e.g. 
because the CRTC is disabled. At the very least, I'd recommend 
double-checking this with Mario Kleiner (Cc'd) and the dri-devel mailing 
list.


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