Touch jumps detected when moving single finger fast
Summary
I can trigger
(EE) event5 - ETPS/2 Elantech Touchpad: kernel bug: Touch jump detected and discarded.
messages in Xorg.log file by striking the touchpad with one finger, very gently and fast.
Steps to reproduce
Strike the touchpad with one finger, very gently and fast. This sometimes generates this debugging message in Xorg.log.
Required information
- libinput version: 1.18.0 (compiled from git tag)
- hardware information: HP laptop 17-by0001nw, Elantech touchpad
-
libinput record
output: record.yml.2021-07-19-21_39_24 -
libinput debug-events --verbose
output: libinput-debug-events.html
Detailed system information
Hardware: HP laptop 17-by0001nw, Elantech touchpad:lip 18 18:44:26 mateusz-ubuntu kernel: psmouse serio1: elantech: assuming hardware version 4 (with firmware version 0x5d4f01)
lip 18 18:44:26 mateusz-ubuntu kernel: psmouse serio1: elantech: Synaptics capabilities query result 0x71, 0x1a, 0x0b.
lip 18 18:44:26 mateusz-ubuntu kernel: psmouse serio1: elantech: Elan sample query result 02, b7, 97
lip 18 18:44:26 mateusz-ubuntu kernel: input: ETPS/2 Elantech Touchpad as /devices/platform/i8042/serio1/input/input5
Software: Ubuntu 20.04, libinput 1.18.0 (compiled from git), Linux 5.13.2 (compiled from source, with one patch to print decoded Elantech touchpad traffic)
udevadm info /sys/class/input/event5:
P: /devices/platform/i8042/serio1/input/input5/event5
N: input/event5
L: 0
S: input/by-path/platform-i8042-serio-1-event-mouse
E: DEVPATH=/devices/platform/i8042/serio1/input/input5/event5
E: DEVNAME=/dev/input/event5
E: MAJOR=13
E: MINOR=69
E: SUBSYSTEM=input
E: USEC_INITIALIZED=30513597
E: ID_INPUT=1
E: ID_INPUT_TOUCHPAD=1
E: ID_INPUT_WIDTH_MM=114
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/e:isa0060/serio1
E: DEVLINKS=/dev/input/by-path/platform-i8042-serio-1-event-mouse
cat /sys/class/dmi/id/modalias
dmi:bvnInsyde:bvrF.63:bd03/25/2021:br15.63:efr74.36:svnHP:pnHPLaptop17-by0xxx:pvrType1ProductConfigId:sku4UF12EA#AKD:rvnHP:rn84CA:rvrKBCVersion74.36:cvnHP:ct10:cvrChassisVersion:
touchpad-edge-detector - OK:
Touchpad ETPS/2 Elantech Touchpad on /dev/input/by-path/platform-i8042-serio-1-event-mouse
Move one finger around the touchpad to detect the actual edges
Kernel says: x [0..3553], y [0..1499]
Touchpad sends: x [6..3553], y [61..1499] |^C|
Touchpad size as listed by the kernel: 114x48mm
User-specified touchpad size: 115x51mm
Calculated ranges: 3547/1438
Suggested udev rule:
[...]
Hello,
As asked in https://wayland.freedesktop.org/libinput/doc/latest/touchpad-jumping-cursors.html , I'm reporting this phenomenon as a bug. Since some time, I was seeing the "Touch jump detected and discarded" messages in Xorg.log. For a long time I did not know when they happen. Finally, I have discovered that they happen as described here.