Code review comment for lp:~oif-team/frame/semi-mt-add-touches

Thanks for the changes, some comments:

* I would prefer clean patches before the changes on top.

* I (again) regret admitting to changing the original kernel protocol to allow zero as a tracking id... :-)

* The semantic change regarding id is fine per se, but needs a lot of thought and checks, because it is, indeed, an ABI break. I will have to get back to you on this one.

* The logic for number of fingers still seems to not handle the full range.