Asus: Touchpad toggle with Fn+F9 doesn't work

[Jeenu V]

I recently upgraded to Mint 17 Mate 64-bit on my Asus X55C from Mint 15. After installation I noticed that Fn key for toggling trackpad doesn't work. It used to work fine on Mint 15. Also it worked fine when I tested Mint 17 on live CD; but somehow stopped to function after installation. Interestingly, other Fn keys work, viz. suspend, increase and decrease volume and brightness, mute etc.; it's only with the trackpad that I face the problem.

Once it got to a point where my touchpad was completely disabled. Following a forum post (http://forums.linuxmint.com/viewtopic.php?f=49&t=176429), I was suggested to add "pci_osi=Linux" to Grub command line. That did help for some time (i.e. Fn+F9 then did use to toggle touchpad) but then after a few days (maybe some packages upgrades went on) it stopped working. Now the only way to toggle touchpad is to go to 'Pointing Devices' and toggle the check box there.

FWIW, I've both acpi and acpi-support packages installed. I can see there are files for ACPI events under /etc/acpi/events but none that relates to trackpad. Also my keyboard layout is set to 'Asus Laptop'.

I'm happy to provide post file, logs or command output here. Please let me know.

Thanks.