In an interesting change of events, the mainline Intel Linux graphics driver has reverted the patch to support XMir -- the X11 compatibility layer for the Mir Display Server in Ubuntu Linux.
This week there was the surprise of the Intel 3.0 Linux DDX driver coming and with it SNA acceleration is enabled by default and it also integrated support for XMir. There's small work needed to the DDX X.Org graphics drivers to be able to support running XMir, similar to XWayland for Wayland users. The support was merged as Canonical said the XMir API should be stable.
However, this morning the XMir work was reverted. In releasing a new 3.0 xf86-video-intel driver snapshot, Intel's Chris Wilson wrote in a Git commit:
Intel, which is a company heavily invested in Wayland and has many full-time employees working on the competing display server (including Kristian Høgsberg, the Wayland founder), now doesn't want any XMir support in their mainline driver. It's interesting to see Intel management force the XMir removal from the Intel driver just days after it was committed and to publicly state a neutral stance on Canonical's controversial display server.
We do not condone or support Canonical in the course of action they have chosen, and will not carry XMir patches upstream.
Canonical will now need to carry the XMir support out-of-tree from the xf86-video-intel driver. Canonical is also carrying patched versions of Mesa, xf86-video-ati, and xf86-video-nouveau for being able to support Mir/XMir in Ubuntu 13.10. The binary AMD and NVIDIA graphics drivers also remain incompatible with Mir.