Re: [PATCH] Input: synaptics - Adjust threshold for treating position values as negative

[Seth Forshee <seth.forshee@canonical.com>]

On Mon, Sep 10, 2012 at 02:10:13PM -0700, Dmitry Torokhov wrote:
> On Monday, September 10, 2012 07:47:07 AM Seth Forshee wrote:
> > Commit c039450 (Input: synaptics - handle out of bounds values from the
> > hardware) caused any hardware reported values over 7167 to be treated as
> > a wrapped-around negative value. It turns out that some firmware uses
> > the value 8176 to indicate a finger near the edge of the touchpad whose
> > actual position cannot be determined. This value now gets treated as
> > negative, which can cause pointer jumps and broken edge scrolling on
> > these machines.
> > 
> > I only know of one touchpad which reports negative values, and this
> > hardware never reports any value lower than -8 (i.e. 8184). Moving the
> > threshold for treating a value as negative up to 8176 should work fine
> > then for any hardware we currently know about, and since we're dealing
> > with unspecified behavior it's probably the best we can do. The special
> > 8176 value is also likely to result in sudden jumps in position, so
> > let's also clamp this to the maximum speicified value for the axis.
> 
> It looks like there is another touchpad that got broken with that "out of 
> bounds" change, see:
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=46371

Thanks for alerting me to the bug, I'll follow up on bugzilla.

Thanks,
Seth