There are two working proof of concept drivers for AM335x touchscreen and for official Raspberry Pi's touchscreen LCD. Proper touchscreen support would consist of userland event reading API, kernel event reporting API, and kernel hardware drivers for specific devices. There is ongoing effort to port Linux evdev API to FreeBSD so applications that use libraries like libinput or tslib could be used without any major changes. Since it's not complete yet I created naive evdev-like API for both kernel and tslib and was able to run demo on Beaglebone Black with 4DCAPE-43T. Once evdev makes it into the tree, both hardware drivers can be modified in "report events" part and committed.