NVIDIA Is Helping To Improve Linux's Dynamic Display Mux Support For Laptops

In addition to NVIDIA engineers being at XDC 2024 in Montreal last week for talking about their Wayland driver plans, there was also a presentation by NVIDIA's Daniel Dadap around current Linux challenges in supporting dynamic display mux hardware on modern laptops with iGPU/dGPU combinations and their hopes for improving the support.

NVIDIA Linux engineers are hoping to see improved support for laptops with dynamic display mux hardware for controlling the GPU(s) actively running and displaying the screen contents. With the likes of VGA_Switcheroo for display mux switching between GPUs there's been problems and they are hoping for a better DRM/KMS API approach. NVIDIA two years ago originally suggested dynamic display mux switching via extending the DRM/KMS API and this remains their desired path. They aren't going into this alone but at this year's DisplayNext Hackfest it was also backed up by AMD for going a similar route.

NVIDIA's DRM-KMS path would overcome VGA_Switcheroo limitations by not depending upon DebugFS and other old design choices, support for N muxes and M muxed connectors, make no assumptions about GPU types but just focused on connectors, and could be integrated with atomic mode-setting.

Within today's Wayland-focused world, Wayland compositors could handle the job of the mux switching policy. As part of this work would need to be done on the compositor side with better multi-GPU support.

For those interested in seeing better dynamic display mux support on Linux for multi-GPU laptops can see the NVIDIA presentation embedded above from XDC 2024 as well as the PDF slide deck.