Mesa Lands DMA-BUF Feedback Support For Vulkan On Wayland
The DMA-BUF Feedback support was added to the Wayland Protocols set last year as an improvement particularly for multi-GPU systems. This Wayland protocol is for communicating information about the GPU device in use by the Wayland compositor and semantics around it such as for use by the secondary GPU with DMA-BUF for efficiently exchanging buffers with the main GPU in a compatible format. The DMA-BUF feedback object introduces the notion of the "main device" and "tranches" as a list of format/modifier pairs that are compatible with the target device. With a tranche it is also indicated whether the buffers allocated with that format/modifier pair can be used for direct scan-out purposes.
The GNOME 42 compositor added DMA-BUF feedback support, Swap / wlroots supports it, and so have other compositors.
Since Mesa 22.0 early this year there has been DMA-BUF feedback support within Mesa's EGL code. Now for Mesa 22.3 coming days ahead of that feature freeze, the year-old merge request adding DMA-BUF feedback support to Mesa's Vulkan windowing system integration (WSI) has been merged.