kern/56576: 9.99.93 regression: synaptics touchpad in RHPS mode

[is%netbsd.org@localhost]

>Number:         56576
>Category:       kern
>Synopsis:       9.99.93 regression: synaptic touchpad in RHPS mode
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Dec 24 20:25:00 +0000 2021
>Originator:     Ignatios Souvatzis
>Release:        NetBSD 9.99.93
>Organization:
>Environment:
[     1.045802] pckbd0 at pckbc1 (kbd slot)
[     1.045802] pckbc1: using irq 1 for kbd slot
[     1.045802] wskbd0 at pckbd0: console keyboard
[     1.045802] pms0 at pckbc1 (aux slot)
[     1.045802] pms0: Synaptics touchpad version 6.2
[     1.045802] pms0: Passthrough, Palm detect, Two button click pad
[     1.045802] pckbc1: using irq 12 for aux slot
[     1.045802] wsmouse0 at pms0 mux 0

hw.synaptics.up_down_emulation = 3
hw.synaptics.up_down_motion_delta = 1
hw.synaptics.gesture_move = 200
hw.synaptics.gesture_length = 20
hw.synaptics.edge_left = 1632
hw.synaptics.edge_right = 5312
hw.synaptics.edge_top = 4288
hw.synaptics.edge_bottom = 1568
hw.synaptics.edge_motion_delta = 32
hw.synaptics.finger_high = 35
hw.synaptics.finger_low = 20
hw.synaptics.two_fingers_emulation = 0
hw.synaptics.scale_x = 16
hw.synaptics.scale_y = 16
hw.synaptics.scale_z = 32
hw.synaptics.max_speed_x = 32
hw.synaptics.max_speed_y = 32
hw.synaptics.max_speed_z = 2
hw.synaptics.movement_threshold = 4
hw.synaptics.movement_enable = 1
hw.synaptics.button_region_movement_enable = 1
hw.synaptics.button_boundary = 2288
hw.synaptics.button2_edge = 2858
hw.synaptics.button3_edge = 4085
hw.synaptics.aux_mid_button_scroll = 1
hw.synaptics.debug = 0

Machine is a 
[     1.000003] LENOVO 7661LN8 (ThinkPad T61)

>Description:
	When reaching the edge of the touchpad, and replacing
the finger somehwere else to continue the motion, the mouse
pointer steps back in the opposite direction some 15% of the
screen size, then continues in the right direction when moving. 

Same effect for all directions.

This doesn't happen with a 9.1_STABLE kernel - the mouse pointer
continues to move in the right direction without any initial jump.

>How-To-Repeat:
	boot system, move finger on touchpad, reach edge, 
	replace finger to more central position.
>Fix:
	Workaround: be very patient, or connect a USB mouse.

>Unformatted:
 	+ riastradh@'s patch for pr 56571