Earlier this month I wrote about the work being done on software rendering in Weston using Pixman. The pixel manipulation library was used to achieve "pure software rendering" and was combined with work on MIT-SHM shared memory support for the X11 back-end. This work allows for Wayland/Weston to run better in non-hardware-accelerated environments.
With a set of patches by Intel's Ander Conselvan de Oliveira, the Pixman renderer is now supported in conjunction with the Weston DRM back-end. "This series adds pixman support to the compositor backend. The bulk of the series consists of recfactoring that backend to make the backend choice implemented on the last patch easier."
This means that the Pixman software renderer can now work directly with the DRM compositor back-end rather than just the X11 back-end atop an existing X.Org Server. Up to now the DRM compositor was just relying upon the OpenGL ES renderer. "If --use-pixman is passed as command line option to weston, the drm backend will use the pixman renderer instead of the gl one."
While the Radeon/Nouveau/Intel DRM drivers have hardware-acceleration, there's plenty of hardware out there that's backed by DRM display drivers but without any hardware GPU acceleration at this point, especially in the ARM/embedded world.
This set of patches are currently floating on the wayland-devel list.