Disabling touchpad buttons on the Thinkpad X120E
By Abhijit Menon-Sen <email@example.com>
One of the two most annoying things about
my Thinkpad X120E is that
the touchpad buttons are flush with the outer edge of the chassis, and
very easy to press inadvertently. I like the touchpad, so the
option of disabling it in the BIOS or with "synclient TouchpadOff=1"
did not appeal to me.
After reading the synclient man page, I was forced to accept that there
was no easy way to disable just the hardware buttons. That left digging
into the source code of the X.Org Synaptics driver ("apt-get source
xserver-xorg-input-synaptics", and I had to install xorg-dev,
xserver-xorg-dev, and xutils-dev as well).
The code is quite pleasant to read, and a single pass through
synaptics.c and some quick grepping suggested a likely approach.
ReadInput() handles each packet received from the device, and it calls
SynapticsGetHwState(), which in turn calls a device-specific
ReadHwState() function (ALPS, PS/2, etc.) to fill in a SynapticsHwState
struct. All I did was to set the left and right click flags to 0 after
--- synaptics.c~ 2012-07-22 13:40:01.522703354 +0530
+++ synaptics.c 2012-07-22 12:30:16.498811737 +0530
@@ -1255,8 +1255,10 @@
SynapticsGetHwState(InputInfoPtr pInfo, SynapticsPrivate *priv,
struct SynapticsHwState *hw)
- return priv->proto_ops->ReadHwState(pInfo, priv->proto_ops,
+ Bool s = priv->proto_ops->ReadHwState(pInfo, priv->proto_ops,
+ hw->left = hw->right = 0;
+ return s;
I built and installed the result (by copying src/.libs/synaptics_drv.so
to /usr/lib/xorg/modules/input), and now I have a working touchpad with
disabled buttons. Tap-to-click is implemented in software, so it works
perfectly. The trackpoint is a separate device altogether, so its
buttons (just above the trackpad) work fine too.
One oddity is that tap-to-click doesn't work at the lightdm
screen, but it works fine inside GNOME. I didn't bother trying to
figure out why.