Hi Arjan,
On Wed, Mar 04, 2009 at 10:55:56PM +0100, Arjan Opmeer wrote:
>
> Recently a user complained that when using the Elantech driver the mouse
> pointer would occasionally jump some distance away, or that when scrolling
> the scrolled page would suddenly jump back a bit.
>
> It turns out that when starting a new touch action on this particular model
> the touchpad does not reliably emit the new coordinates but can repeat one
> or two of the coordinates of the last release point. This misreporting can
> last several motion packets depending on the number of fingers that are
> touching.
>
> We came up with a workaround that basically discards mouse packets as long
> as the number of fingers is increasing. Like so:
>
>
> if (fingers > old_fingers) {
> discard packet
> }
>
> With this fix in place the user no longer suffers from the jumpy mouse
> cursor or the jumpy scrolling. He reports no impact on the responsiveness of
> the touchpad.
>
> My question now is whether this is the right approach to fix this issue? Is
> such a workaround acceptable and should it live in the kernel? Can or should
> this problem be better solved in the Xorg Synaptics driver?
>
This is purely hardware problem and I believe it should be fixed in the
kernel; userspace should not be aware that device may emit wrong
coordinates.
Thanks!
--
Dmitry
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