This weekend, I announced the first implementation of XI2 on the xorg-devel list.
You can get the repositories from
Check out the xi2 branch on all four repositories.
XI2 is important for two reasons. One, it's the client-side API that enables applications to make use of MPX. For obvious reasons, I have some interest in getting this done.
The other part of XI2 (and why it is called XI2) is that it's a new version of the X Input Extension. One of the goals here is a cleaned up API that is less painful to use than the first, current, version.
Aside from some API cleanup, the new additions are subpixel precision in events, the ability to support devices that change capabilities at runtime and relative device events. And of course all the stuff required to access MPX' functionality.
So, if you're adventurous*, grab the repositories, compile them up and test them. You can write little test apps to play around with the new stuff, and if you find any problems or inconsistencies, please report them back. I'm trying really hard to get this right.
Note that because this is the first version, API changes are to be expected and there will be the odd bug in there.
* One of the main goals of MPX (and XI2) is that it must be invisible until used. So you can grab the repositories and run your everyday desktop off it and there should be no difference.