On 5/15/26 13:55, Thomas Zimmermann wrote: > DRM's WAIT_VBLANK ioctl synchronizes user-space clients to display > refresh. This is meaningless with vblank timers, which run unrelated > to the hardware's vblank. > > Disable the ioctl for simulated vblanks. Set DRM_VBLANK_FLAG_SIMULATED > for CRTCs with simulated vblank events in all such drivers. The vblank > timers of these devices still rate-limit the number of page-flip events > to match the display refresh. > > According to maintainers, user-space compositors do not require the ioctl > for rate-limitting display output. Weston and Kwin rely on page-flip > events. Mutter uses and internal timer to limit the number of display > updates per second.
Actually mutter fundamentally relies on atomic commit completion events for that, same as Weston & KWin. Mutter uses the WAIT_VBLANK ioctl only for minimizing input → output latency (which can hide issues when completion of atomic commits isn't properly throttled). (Just a side not on the cover letter, no objections to the patches themselves) -- Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer https://redhat.com \ Libre software enthusiast
