Touchscreen not working on bq-paella with mainline kernel

Describe your issue

What's the expected behaviour?

touch events should be registered by libinput

What's the current behaviour?

touchscreen is registered as devices/platform/soc/78b9000.i2c/i2c-1/1-0048/input/input3 according to dmesg.
tested the device with libinput record -> no touch events are received

How to reproduce your issue?

built the image according to the wiki page for the device
flash image

What device are you using?

bq-paella
BQ Aquaris X5 (android version)

On what postmarketOS version did you encounter the issue?

• edge (master branch)
• stable (v20.05 branch)

On what environment did you encounter the issue?

Phone environments

• Phosh
• Plasma Mobile
• Sxmo

Other

• No environment
• GNOME
• KDE Plasma
• Kodi
• MATE
• Shelli
• Sway
• Weston
• Xfce4
• fbkeyboard
• i3wm

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in dd-mm-yyyy format)

10-10-2020

Additional information

The devices boots and functions fine otherwise.
As stated above it is the android version of the device not the CyanogenMod Edition.
Maybe it uses a different touchscreen hardware?

pmbootstrap init -> init.txt
dmesg -> dmesg
libinput record -> libinput
uname -a -> Linux bq-paella 5.9.0-rc7-postmarketos-qcom-msm8916 #1 SMP PREEMPT Mon Oct 5 00:48:10 UTC 2020 aarch64 Linux
reading from the device with cat /dev/input/event3 also produces no output