Ran into this problem when converting my ThinkPad. The default distribution of xorg-server includes 10-evdev.conf in it's config directory. As a result, even when we have a system that doesn't have xf86-input-evdev installed onto it, xorg attempts to default to all applicable input drivers using evdev, which can be a problem if we want to use libinput instead of evdev. I think a better solution for installing these configs would be to include them in xf86-input-evdev instead of the base xorg-server package.
http://patchwork.freedesktop.org/patch/48520/ http://patchwork.freedesktop.org/patch/48519/
xf86-input-evdev: commit 66c997886424a20e92ce30fcfda46cbb5c7352ab Author: Peter Hutterer <peter.hutterer@who-t.net> Date: Tue May 5 15:34:07 2015 +1000 Add the default evdev config
commit fc59c8fe8d941b0ec1e98c59bc57b1f97dba149d Author: Peter Hutterer <peter.hutterer@who-t.net> Date: Tue May 5 15:54:20 2015 +1000 config: remove 10-evdev.conf, let the evdev driver install that file
Note to downstream (I'm not a developer of freedesktop.org): This patch is not (yet?) included in xorg-server 1.17 branch as of Nov 2015, including 1.17.4. If you want to use xf86-input-evdev >= 2.10, wait for xorg-server 1.18, or delete 10-evdev.conf from xorg-server manually.
fwiw, I'm not planning to backport this to 1.17, it has the potential to break existing 1.17 installations if they have not updated to a newer evdev version. A file conflict is usually easily detected in packaging system but if the file is missing nothing will complain and the user may be left without any input devices.
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