Vishnu Sankar has been leading the effort of TrackPoint double-tap handling under Linux with better integration between the Trackpoint driver and ThinkPad ACPI driver code. Double-tap support requires cooperation with the firmware and for recognizing the hardware's support. With these patches doubletap support would be enabled by default on capable devices while a sysfs control allows for toggling the feature if so desired.
This double-tap functionality in turn works and can be toggled without any user-space configuration. The sysfs file is /sys/devices/platform/thinkpad_acpi/doubletap_enable for setting it to 0 if wanting to disable double-tap hotkey events or 1 to allow for the double-tap hotkey events, as is the default. Previously the thinkpad_acpi code just unconditionally enabled the double-tap support.
The v6 patches out today just bring a documentation formatting fix, so it's looking like this cleaned-up TrackPoint double-tap code is settling down and could soon be ready for the mainline kernel.