X.Org Modesetting Driver Will Now Better Handle Multi-Montior Mixed-VRR Setups

The xf86-video-modesetting DDX driver that is commonly in use for systems running an X.Org Server will soon find better support if you have a multi-monitor configuration where only some displays can support variable rate refresh (VRR / Adaptive-Sync / FreeSync).

When the X.Org modesetting driver currently encounters a multi-monitor system where some displays are VRR capable and others not, the VRR-capable property was being set simply on whatever the last added DRM output could support. So depending upon whether the VRR-capable monitor was plugged in last or not would impact whether you could make use of it with this generic driver.

Thanks to developer Mario Kleiner he has fixed up this behavior for hybrid systems having some VRR capable displays. Now with the latest Git code, if there is at least one VRR-capable display the driver will treat the X screen as such irregardless of the plugging order.

This was fixed up in this commit today to the X.Org Server code-base where xf86-video-modesetting resides. This is also useful for the recently added AsyncFlipSecondaries feature for a vblank-synced flip on the primary display while all other displays will try to flip async/immediately and not synchronized to the central vblank.