Cyril

It seems same problem here: https://gitlab.freedesktop.org/libinput/libinput/issues/199
seems much better by correcting jitter in /etc/udev/hwdb.d/99-touchpad-fuzz-override.hwdb
changing touchpad touch range has effect as well, but doesn’t seem to take effect unless .quirks file is located in /usr/share/libinput* directory

---

Prereqs:
zypper install libinput-tools
pip3 install libevdev

find the device event

sudo libinput list-devices
[ ... ]
Device:           SynPS/2 Synaptics TouchPad
Kernel:           /dev/input/event1
Group:            11
Seat:             seat0, default
Size:             98x48mm
Capabilities:     pointer gesture
Tap-to-click:     disabled
Tap-and-drag:     enabled
Tap drag lock:    disabled
Left-handed:      disabled
Nat.scrolling:    disabled
Middle emulation: n/a
Calibration:      n/a
Scroll methods:   *two-finger edge 
Click methods:    none
Disable-w-typing: enabled
Accel profiles:   none
Rotation:         n/a

list quirks for the trouble device

libinput quirks list /dev/input/event1
ModelSynapticsSerialTouchpad=1

quirk listed above, found at /usr/share/libinput*/libinput

/usr/share/libinput-1.12.6/libinput
cat 30-vendor-synaptics.quirks
# Do not edit this file, it will be overwritten on update

[Synaptics Serial Touchpads]
MatchUdevType=touchpad
MatchBus=ps2
MatchVendor=0x0002
MatchProduct=0x0007
ModelSynapticsSerialTouchpad=1

which reads not to edit, so apply changes to an /etc-override file
/etc/libinput/local-overrides.quirks

[Synaptics Touchpad override]
MatchUdevType=touchpad
MatchBus=ps2
MatchVendor=0x0002
MatchProduct=0x0007
AttrPressureRange=25:24
AttrPalmSizeThreshold=120

/usr/share/libinput-1.12.6/libinput
libinput quirks list /dev/input/event1

ModelSynapticsSerialTouchpad=1
AttrPalmSizeThreshold=120
AttrPressureRange=25:24

per [jitter section]: /etc/udev/hwdb.d/99-touchpad-fuzz-override.hwdb

# DellInc. SynPS/2 Synaptics TouchPad
evdev:name:SynPS/2 Synaptics TouchPad:dmi:*svnDellInc.:pnInspiron5423*
 EVDEV_ABS_00=::41:24
 EVDEV_ABS_01=::43:24
 EVDEV_ABS_35=::41:24
 EVDEV_ABS_36=::43:24

/usr/share/libinput-1.12.6/libinput
udevadm info /sys/class/input/event1

P: /devices/platform/i8042/serio1/input/input2/event1
N: input/event1
L: 0
S: input/by-path/platform-i8042-serio-1-event-mouse
E: DEVPATH=/devices/platform/i8042/serio1/input/input2/event1
E: DEVNAME=/dev/input/event1
E: MAJOR=13
E: MINOR=65
E: SUBSYSTEM=input
E: USEC_INITIALIZED=7345768
E: ID_INPUT=1
E: ID_INPUT_TOUCHPAD=1
E: ID_INPUT_WIDTH_MM=98
E: ID_INPUT_HEIGHT_MM=48
E: ID_BUS=i8042
E: ID_SERIAL=noserial
E: ID_PATH=platform-i8042-serio-1
E: ID_PATH_TAG=platform-i8042-serio-1
E: ID_INPUT_TOUCHPAD_INTEGRATION=internal
E: LIBINPUT_DEVICE_GROUP=11/2/7:isa0060/serio1
E: LIBINPUT_FUZZ_35=8
E: LIBINPUT_FUZZ_36=8
E: DEVLINKS=/dev/input/by-path/platform-i8042-serio-1-event-mouse

The actual hwdb is stored in binary file on-disk and must be updated manually whenever a .hwdb file changes

restarting hardware database:

1. update the binary
   sudo systemd-hwdb update
2. trigger a reload of device properties:
   sudo udevadm trigger /sys/class/input/event1
3. verify changes:
   udevadm info /sys/class/input/event1

ref: https://wayland.freedesktop.org/libinput/doc/latest/device-configuration-via-udev.html#reloading-the-hwdb

jitter section