touchpad not detected

Touchpad is not detected at all, there's no touchpad device in "/proc/bus/input/devices".

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-48-generic 5.4.0-48.52
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.8
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: chenchifan 1002 F.... pulseaudio
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Sat Oct 3 13:37:30 2020
InstallationDate: Installed on 2020-08-12 (51 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
MachineType: LENOVO 81Q7
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-48-generic root=UUID=79381bd5-78f8-44f3-b125-714ee8298ab5 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-48-generic N/A
 linux-backports-modules-5.4.0-48-generic N/A
 linux-firmware 1.187.3
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/03/2019
dmi.bios.vendor: LENOVO
dmi.bios.version: AKCN31WW
dmi.board.asset.tag: No Asset Tag
dmi.board.name: LNVNB161216
dmi.board.vendor: LENOVO
dmi.board.version: SDK0J40709 WIN
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo Yoga S940-14IWL
dmi.modalias: dmi:bvnLENOVO:bvrAKCN31WW:bd04/03/2019:svnLENOVO:pn81Q7:pvrLenovoYogaS940-14IWL:rvnLENOVO:rnLNVNB161216:rvrSDK0J40709WIN:cvnLENOVO:ct10:cvrLenovoYogaS940-14IWL:
dmi.product.family: Yoga S940-14IWL
dmi.product.name: 81Q7
dmi.product.sku: LENOVO_MT_81Q7_BU_idea_FM_Yoga S940-14IWL
dmi.product.version: Lenovo Yoga S940-14IWL
dmi.sys.vendor: LENOVO