As I wrote on the mailing list:
> KDE: limits itself to standard X11 mouse config interfaces, no changes needed.
Not true. We ship kcm_touchpad on the KDE spin, which definitely does depend on synaptics interfaces (search for "synaptics" in: https://projects.kde.org/projects/playground/utils/kcm-touchpad/repository/revisions/master/entry/src/backends/x11/xlibbackend.cpp ). Anything that does not use the synaptics driver is not considered a touchpad. And kcm_touchpad is also in the process of becoming a core part of upstream Plasma. (It is currently in the git.kde.org playground.)
Therefore, porting kcm_touchpad (the rewritten 1.x series we currently ship, not the old, obsolete, 0.3.x version, please make sure you look at the correct version) is an essential requirement before we can move away from the synaptics driver.
An additional objection I have to this change proposal is that libinput (deliberately) only implements a small subset of the configurability of the old drivers, and thus, if we are going to remove the old drivers entirely, we are taking away flexibility from our users. --Kkofler (talk) 17:07, 15 December 2014 (UTC)