kern/56481: synaptics: since r1.73, sc->ext_middle gets "stuck down"

[nia%pkgsrc.org@localhost]

>Number:         56481
>Category:       kern
>Synopsis:       synaptics: since r1.73, sc->ext_middle gets "stuck down"
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Oct 31 08:35:00 +0000 2021
>Originator:     nia
>Release:        NetBSD 9.99.92 amd64
>Organization:
The NetBSD Foundation
>Environment:
NetBSD 9.99.92 amd64
>Description:
Since the recent rework, sc->ext_middle gets "stuck down"
when the middle button on my ThinkPad X250 touchpad is pressed.
This makes subsequent middle clicks impossible and causes all
TrackPoint movement to be interpreted as scrolling.
>How-To-Repeat:

>Fix: