Another Shot At The KMS Page-Flipping Ioctl

Being worked on for the past several months by Kristian Høgsberg and other developers has been the KMS page-flipping ioctl, which makes it possible for kernel mode-setting drivers to benefit from tear-free updating of the screen with low-latency page-flipping. This kernel DRM ioctl is also a requirement for the Wayland Display Server. The page-flipping ioctl should have made it into the Linux 2.6.32 kernel, but it didn't end up happening due to some last minute work.

This afternoon though Kristian has republished his kernel mode-setting page-flipping ioctl patch with the latest changes. This latest patch incorporates blocking within the kernel and optional events to user-space. Moving the blocking from user-space into the kernel allows other processes to use the GPU while waiting for the page flip at the next vblank.

This DRM ioctl patch touches about 400 lines of code (mostly the addition of new code) and is now hopefully ready to enter the Linux 2.6.33 kernel, which is great news for those using the X Server and also those wanting to experiment with Wayland but have been waiting for more of the work to land in mainline trees. The Linux 2.6.33 kernel will be the first release in 2010.

This latest page-flipping ioctl patch can be found on the DRI development list.