NVIDIA Engineer Sends Out Patches For Supporting Sync FDs + Sync Objects With Nouveau

Longtime NVIDIA engineer Thierry Reding who has been involved with the open-source Nouveau driver efforts largely from an embedded/mobile Tegra angle last week sent out the newest patch series.

The latest work by Reding is focused on supporting synchronization file descriptors (sync FDs) and synchronization objects (syncobj) with the Nouveau DRM kernel driver.

A new kernel interface is proposed for submitting push buffers that can optionally return a sync FD or sync object to user-space. These synchronization FDs/objects are practical for synchronization operations between the GPU and other drivers like KMS display code.

While the synchronization objects are relevant to an array of use-cases, the initial motivation from the NVIDIA side at least is making use of this new kernel interface for being able to implement eglDupNativeFenceFDANDROID as exposed by the EGL_ANDROID_native_fence_sync extension. EGL_ANDROID_native_fence_sync is similar to KHR_fence_sync.

Reding has been hosting patches for two years already to make use of the sync FD interface by user-space with libdrm and Mesa patches to the Nouveau driver. His testing has been focused on the atomic kmscube program and the Weston reference compositor to Wayland.

The kernel-side work to this Nouveau synchronization objects/file-descriptors work can be found via this patch series and could potentially see mainline as soon as Linux 5.10.