Panasonic CF-18/19 (Toughbook) Tablet Button driver for Linux
cd /usr/local/src/
git clone https://github.com/x-magic/panasonic-hbtn.git
cd panasonic-hbtn
make all
make install
depmod -a
modprobe panasonic-hbtn
Then try out if those buttons are in working order.
Finally,
update-initramfs -u
Tested with CF-19C MK1 with Ubuntu 15.10 i386 desktop.