Comment # 16 on bug 1098392 from Larry Finger

I have completed the bisection. Although it sounds improbable, the bad commit
is

commit 04bb1719c4de94700056241d4c0fe3c1413f5aff
Author: Ondrej Zary <linux@rainbow-software.org>
Date:   Tue Apr 3 10:24:34 2018 -0700

    Input: i8042 - enable MUX on Sony VAIO VGN-CS series to fix touchpad

    The touch sensor buttons on Sony VAIO VGN-CS series laptops (e.g.
    VGN-CS31S) are a separate PS/2 device. As the MUX is disabled for all
    VAIO machines by the nomux blacklist, the data from touch sensor
    buttons and touchpad are combined. The protocol used by the buttons is
    probably similar to the touchpad protocol (both are Synaptics) so both
    devices get enabled. The controller combines the data, creating a mess
    which results in random button clicks, touchpad stopping working and
    lost sync error messages:
    psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 4
    psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1
    psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1
    psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1
    psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1
    psmouse serio1: issuing reconnect request

    Add a new i8042_dmi_forcemux_table whitelist with VGN-CS.
    With MUX enabled, touch sensor buttons are detected as separate device
    (and left disabled as there's currently no driver), fixing all touchpad
    problems.

    Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
    Cc: stable@vger.kernel.org
    Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

At this point, I have no idea how a fix for Sony VAIO boxes affects my Toshiba
hardware, but the bisection was straight forward. Apparently, the patch affects
more touchpads than that of Sony.