Re: [PATCH 6/9 v2] Input: synaptics - process finger (<=3) transitions

On 07/20/2011 06:39 AM, djkurtz@chromium.org wrote:

From: Daniel Kurtz <redacted>

Synaptics image sensor touchpads track 5 fingers, but only report 2.

This patch attempts to deal with some idiosyncrasies of these touchpads:

 * When there are 3 or more fingers, only two are reported.
 * The number of fingers can change at any time, but is only reported in
   SGM packets, thus at a number-of-fingers change, it is not possible
   to tell whether the AGM finger is for the original or new number of
   fingers.
 * When the number of fingers changes from 2->3 it is not
   possible to tell which of the 2 fingers are now reported.
 * When number of fingers changes from 3->2 it is often not possible to
   tell which finger was removed, and which are now being reported.

When 2 or more packets are present on the touchpad, the kernel reports

                 ^touches or fingers