[PATCH libinput 5/9] udev: add Elantech touchpad firmware detection

Bill Spitzak spitzak at gmail.com
Thu Jul 9 13:09:35 PDT 2015

On Wed, Jul 8, 2015 at 8:29 PM, Peter Hutterer <peter.hutterer at who-t.net>

> good point, that does seem to be the best approach here.
> the resolution claimed was 800 dpi -> 31 u/mm.
> I'm a bit worried about doing this though, the reporter in
> https://bugs.freedesktop.org/show_bug.cgi?id=90101
> measured a touchpad size of 86x44mm, at 31 u/mm the touchpad only comes to
> 80x34mm. That's not promising, but then again it's not the first touchpad
> that's confused about its size.
> So we may have to override this for some devices anyway.

800 dpi =  ~31.496 u/mm

That is really close to 31.5, which produces the biggest error when
rounding to an integer.
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