Kristian Høgsberg began merging his DRI2 code in February and then he merged the remaining bits in late March that provided the direct rendering support. However, then came Intel's Graphics Execution Manager.
The Graphics Execution Manager (or commonly known as GEM) is a kernel memory manager developed by Intel for their graphics driver and a complete replacement for Tungsten's TTM. Up to that point, TTM was set to become the de facto memory manager for use by open-source X.Org drivers. With that said, the initial design of DRI2 had required TTM's memory manager to be used. When Intel jumped ship on TTM it presented the need for DRI2 to be reworked. As a result of this, DRI2 support was dropped from the X Server 1.5 / X.Org 7.4 release.
Since then DRI2 has been reworked to accommodate GEM. Those bits had entered the different development trees in late August. At this year's X Developers' Summit (X Developers Raid The Zoo), a few more improvements were agreed to between Kristian and the other developers. Today this latest batch of improvements have been merged.
Prior to leaving on a holiday, Kristian committed the new DRI2 protocol and documentation along with updates to the X Server, Mesa, and Intel driver.
What's been added in this latest Direct Rendering Infrastructure 2 push is a DRI2CopyRegion request and the framework that allows DRI2 to be extended in future versions. With the CopyRegion request it's mostly a rename from SwapBuffers. No vsync handling or page-flipping support has yet been added to DRI2.
After today's commits, Kristian is now comfortable letting DRI2 be merged to master in Intel's X.Org driver. No other drivers, however, have yet to fully adopt this latest version. Intel users though will need to enable the DRI2 support through their xorg.conf. Kristian hopes to have most of the DRI2 work settled by next month. With X Server 1.6 being planned for a December release, the timing should be ideal. The announcement regarding today's DRI2 update can be read on the X.Org mailing list.