Touchpad stopped working after upgrade to 4.15.0-72-generic

[cohomology84]

I am running Ubuntu 18.04.3 on a Dell XSP12 laptop. After an automatic kernel update from 4.15.0-70-generic to 4.15.0-72-generic, my touchpad stopped working. (The mouse pointer is not moving, and I cannot click.) The touchpad is still working when I start up with the older kernel.

I think it's a Synaptics touchpad. The output of 'xinput list' when running either kernel is as follows:

⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ ATML1000:00 03EB:842F id=11 [slave pointer (2)]
⎜ ↳ Synaptics s3203 id=12 [slave pointer (2)]
⎜ ↳ PS/2 Generic Mouse id=16 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
    ↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
    ↳ Power Button id=6 [slave keyboard (3)]
    ↳ Video Bus id=7 [slave keyboard (3)]
    ↳ Power Button id=8 [slave keyboard (3)]
    ↳ Integrated Webcam: Integrated W id=9 [slave keyboard (3)]
    ↳ Intel Virtual Button driver id=10 [slave keyboard (3)]
    ↳ Dell WMI hotkeys id=13 [slave keyboard (3)]
    ↳ AT Translated Set 2 keyboard id=14 [slave keyboard (3)]
    ↳ DELL Wireless hotkeys id=15 [slave keyboard (3)]

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-72-generic 4.15.0-72.81
ProcVersionSignature: Ubuntu 4.15.0-72.81-generic 4.15.18
Uname: Linux 4.15.0-72-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: marcus 1546 F.... pulseaudio
 /dev/snd/controlC1: marcus 1546 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Sun Dec 8 13:55:23 2019
HibernationDevice: RESUME=UUID=07196a12-9711-4352-816d-530ed0fe9c00
InstallationDate: Installed on 2019-04-29 (222 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
MachineType: Dell Inc. XPS 12-9Q33
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-72-generic root=UUID=fa2cb087-82ac-4ae2-94ca-9cdc35006815 ro quiet splash vt.handoff=1
RelatedPackageVersions:
 linux-restricted-modules-4.15.0-72-generic N/A
 linux-backports-modules-4.15.0-72-generic N/A
 linux-firmware 1.173.12
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/03/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A08
dmi.board.name: XPS 12-9Q33
dmi.board.vendor: Dell Inc.
dmi.board.version: A08
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: Not Specified
dmi.modalias: dmi:bvnDellInc.:bvrA08:bd03/03/2015:svnDellInc.:pnXPS12-9Q33:pvrA08:rvnDellInc.:rnXPS12-9Q33:rvrA08:cvnDellInc.:ct8:cvrNotSpecified:
dmi.product.name: XPS 12-9Q33
dmi.product.version: A08
dmi.sys.vendor: Dell Inc.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

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