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

[Peter Hutterer]

On Thu, Jul 09, 2015 at 01:09:35PM -0700, Bill Spitzak wrote:
> On Wed, Jul 8, 2015 at 8:29 PM, Peter Hutterer <peter.hutterer at who-t.net>
> wrote:
> 
> >
> > 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.

true, but we're talking about an error rate of less than 0.02mm here. on a
touchpad. it doesn't really matter.

Cheers,
   Peter