Does touchpads have buttons?

[Søren Hauberg]

Hi,
  I'm trying to differentiate touchpads from touchscreens in the evdev
driver. Both types of devices has absolute axis, and emit the
BTN_TOUCH signal. So, I need something else to tell them apart.
Unfortunately, I don't have access to a touchpad (the only one I have
is broken), so I can't figure out if such a device has other
interesting properties. So, my question is: does touchpads have
buttons, i.e. do they emit BTN_LEFT? Touchscreens don't (at least the
ones using the 'usbtouchscreen' kernel module doesn't), so I might be
able to use this as a differentiator.

Thanks,
Søren