Message-ID: <4c0a34ca-145b-4037-8325-860ed55f1700@web.de>
Date: Tue, 23 Dec 2025 20:35:17 +0100
From: Mirco Kramer <mircomat@....de>
To: jkosina@...e.cz, bentiss@...nel.org, linux-input@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Subject: [REGRESSION] Touchpad stops working on Trekstor Primebook C13 after
 Kernel 6.8.0-51

Subject: [REGRESSION] Touchpad stops working on Trekstor Primebook C13 
after Kernel 6.8.0-51

*Description:* After updating from kernel 6.8.0-51 to 6.8.0-68, the 
touchpad on my Trekstor Primebook C13 was no longer functional. It 
appears to be an issue with the i2c-hid subsystem on the Apollo Lake 
platform.

*Specific Symptom:* > "In 6.8.0-68 and -90, the touchpad fails to track 
a single finger. However, if a second finger is placed stationary on the 
touchpad surface, the first finger can move the cursor normally. This 
suggests a regression in I2C-HID interrupt handling or event filtering 
(possibly related to 'Confidence' bits or 'Contact' reporting)."

*Regression:*
    Last known working kernel: 6.8.0-51
    First known broken kernel: 6.8.0-68

*Hardware:*

    Device: Trekstor Primebook C13
    Bus: I2C (HID-over-I2C)

*Additional Info:* I suspect a change in the i2c-designware or i2c-hid 
drivers between these sub-versions might be the cause.

System:
   Kernel: 6.8.0-51-generic arch: x86_64 bits: 64 compiler: gcc v: 13.3.0
     clocksource: tsc
   Desktop: MATE v: 1.26.2 wm: marco v: 1.26.2 with: mate-panel
     tools: mate-screensaver vt: 7 dm: LightDM v: 1.30.0
     Distro: Linux Mint 22.2 Zara base: Ubuntu 24.04 noble
Machine:
   Type: Convertible System: TREKSTOR product: Primebook C13 v: N/A
     serial: <superuser required>
   Mobo: TS_weibu model: Apollolake_alk_V01 serial: <superuser required>
     part-nu: CFALKWW02464 uuid: <superuser required> UEFI: American 
Megatrends
     v: BIOS_V1.2.9_20171026 date: 10/26/2017
Battery:
   ID-1: BAT0 charge: 26.4 Wh (66.0%) condition: 40.0/40.0 Wh (100.0%)
     power: 4.2 W volts: 7.4 min: N/A model: Intel SR 1 SR Real Battery
     type: Unknown serial: <filter> status: discharging
CPU:
   Info: dual core model: Intel Celeron N3350 bits: 64 type: MCP
     smt: <unsupported> arch: Goldmont rev: 9 cache: L1: 112 KiB L2: 2 MiB
   Speed (MHz): avg: 798 high: 800 min/max: 800/2400 cores: 1: 796 2: 800
     bogomips: 4377
   Flags: ht lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx
Graphics:
   Device-1: Intel HD Graphics 500 driver: i915 v: kernel arch: Gen-9 
ports:
     active: eDP-1 empty: DP-1,HDMI-A-1 bus-ID: 00:02.0 chip-ID: 8086:5a85
     class-ID: 0300
   Device-2: Alcor Micro USB 2.0 PC Camera driver: snd-usb-audio,uvcvideo
     type: USB rev: 2.0 speed: 480 Mb/s lanes: 1 bus-ID: 1-8:4 chip-ID: 
058f:3841
     class-ID: 0102
   Display: x11 server: X.Org v: 21.1.11 with: Xwayland v: 23.2.6
     compositor: marco v: 1.26.2 driver: X: loaded: modesetting
     unloaded: fbdev,vesa dri: iris gpu: i915 display-ID: :0 screens: 1
   Screen-1: 0 s-res: 1600x900 s-dpi: 96 s-size: 423x238mm (16.65x9.37")
     s-diag: 485mm (19.11")
   Monitor-1: eDP-1 model: Najing CEC Panda LC133LF2L01 res: 1600x900 
hz: 60
     dpi: 138 size: 294x165mm (11.57x6.5") diag: 337mm (13.3") modes: 
1920x1080
   API: EGL v: 1.5 hw: drv: intel iris platforms: device: 0 drv: iris
     device: 1 drv: swrast gbm: drv: iris surfaceless: drv: iris x11: 
drv: iris
     inactive: wayland
   API: OpenGL v: 4.6 compat-v: 4.5 vendor: intel mesa
     v: 25.0.7-0ubuntu0.24.04.2 glx-v: 1.4 direct-render: yes renderer: 
Mesa
     Intel HD Graphics 500 (APL 2) device-ID: 8086:5a85
Audio:
   Device-1: Intel Celeron N3350/Pentium N4200/Atom E3900 Series Audio 
Cluster
     driver: snd_hda_intel v: kernel bus-ID: 00:0e.0 chip-ID: 8086:5a98
     class-ID: 0403
   Device-2: Alcor Micro USB 2.0 PC Camera driver: snd-usb-audio,uvcvideo
     type: USB rev: 2.0 speed: 480 Mb/s lanes: 1 bus-ID: 1-8:4 chip-ID: 
058f:3841
     class-ID: 0102
   API: ALSA v: k6.8.0-51-generic status: kernel-api
   Server-1: PipeWire v: 1.0.5 status: active with: 1: pipewire-pulse
     status: active 2: wireplumber status: active 3: pipewire-alsa type: 
plugin
Network:
   Device-1: Intel Wireless 3165 driver: iwlwifi v: kernel pcie:
     speed: 2.5 GT/s lanes: 1 bus-ID: 01:00.0 chip-ID: 8086:3165 
class-ID: 0280
   IF: wlp1s0 state: up mac: <filter>
Bluetooth:
   Device-1: Intel Bluetooth wireless interface driver: btusb v: 0.8 
type: USB
     rev: 2.0 speed: 12 Mb/s lanes: 1 bus-ID: 1-7:3 chip-ID: 8087:0a2a
     class-ID: e001
   Report: hciconfig ID: hci0 rfk-id: 1 state: down
     bt-service: enabled,running rfk-block: hardware: no software: yes
     address: <filter>
Drives:
   Local Storage: total: 87.97 GiB used: 33.99 GiB (38.6%)
   ID-1: /dev/mmcblk0 vendor: HP model: DF4064 size: 58.24 GiB
     type: Removable tech: SSD serial: <filter> fw-rev: 0x8 scheme: GPT
   ID-2: /dev/mmcblk1 model: SU32G size: 29.72 GiB type: USB tech: SSD
     serial: <filter> scheme: MBR
Partition:
   ID-1: / size: 56.53 GiB used: 30.52 GiB (54.0%) fs: ext4 dev: 
/dev/mmcblk0p2
   ID-2: /boot/efi size: 511 MiB used: 6.1 MiB (1.2%) fs: vfat
     dev: /dev/mmcblk0p1
Swap:
   ID-1: swap-1 type: file size: 3.98 GiB used: 738.2 MiB (18.1%) 
priority: -2
     file: /swapfile
Sensors:
   System Temperatures: cpu: 46.0 C mobo: N/A
   Fan Speeds (rpm): N/A
Repos:
   Packages: 1931 pm: dpkg pkgs: 1923 pm: flatpak pkgs: 8
   No active apt repos in: /etc/apt/sources.list
   Active apt repos in: 
/etc/apt/sources.list.d/official-package-repositories.list
     1: deb https://ftp.fau.de/mint/packages zara main upstream import 
backport
     2: deb http://ftp.fau.de/ubuntu noble main restricted universe 
multiverse
     3: deb http://ftp.fau.de/ubuntu noble-updates main restricted 
universe multiverse
     4: deb http://ftp.fau.de/ubuntu noble-backports main restricted 
universe multiverse
     5: deb http://security.ubuntu.com/ubuntu/ noble-security main 
restricted universe multiverse
   Active apt repos in: /etc/apt/sources.list.d/teamviewer.list
     1: deb [signed-by=/usr/share/keyrings/teamviewer-keyring.gpg] 
https://linux.teamviewer.com/deb stable main
Info:
   Memory: total: 4 GiB available: 3.66 GiB used: 2.55 GiB (69.7%)
   Processes: 227 Power: uptime: 48m states: freeze,mem,disk suspend: deep
     wakeups: 0 hibernate: platform Init: systemd v: 255 target: 
graphical (5)
     default: graphical
   Compilers: gcc: 13.3.0 Shell: Bash v: 5.2.21 running-in: mate-terminal
     inxi: 3.3.34

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