How to get xinput device ID of touchscreen without using manufacturer string?

[Sagar Biddanda]

Chromium only shows proper touchscreen behavior when the supplied ID argument is 7 in the case of the below devices. Note that the xinput IDs are subject to change during a reboot, so I can't just use 7 all the time.

I understand I can whitelist manufacturer strings but I would like something reliable that always works and doesn't depend on manufacturer strings staying the same.


DEVICE 1:

Touchscreen Hardware on device 1 (reported by xinput):
? Virtual core pointer id=2 [master pointer (3)]
? ? Virtual core XTEST pointer id=4 [slave pointer (2)]
? ? ADS7846 Touchscreen id=9 [slave pointer (2)]
? ? NHD Newhaven Display id=7 [slave pointer (2)]
? Virtual core keyboard id=3 [master keyboard (2)]
? Virtual core XTEST keyboard id=5 [slave keyboard (3)]
? 30370000.snvs:snvs-powerkey id=6 [slave keyboard (3)]
? Dell Dell USB Entry Keyboard id=8 [slave keyboard (3)]


/dev/input/touchscreen0 -> /dev/input/event1


udevadm info --query=property --name=/dev/input/event1
DEVLINKS=/dev/input/by-id/usb-NHD_Newhaven_Display-event-if00 /dev/input/by-path/platform-ci_hdrc.0-usb-0:1:1.0-event /dev/input/touchscreen0
DEVNAME=/dev/input/event1
DEVPATH=/devices/soc0/soc/30800000.aips-bus/30b10000.usb/ci_hdrc.0/usb1/1-1/1-1:1.0/0003:0461:0022.005C/input/input93/event1
ID_BUS=usb
ID_INPUT=1
ID_INPUT_TOUCHSCREEN=1
ID_MODEL=Newhaven_Display
ID_MODEL_ENC=Newhavenx20Displayx20
ID_MODEL_ID=0022
ID_PATH=platform-ci_hdrc.0-usb-0:1:1.0
ID_PATH_TAG=platform-ci_hdrc_0-usb-0_1_1_0
ID_REVISION=0100
ID_SERIAL=NHD_Newhaven_Display
ID_TYPE=hid
ID_USB_DRIVER=usbhid
ID_USB_INTERFACES=:030102:
ID_USB_INTERFACE_NUM=00
ID_VENDOR=NHD
ID_VENDOR_ENC=NHD
ID_VENDOR_ID=0461
LIBINPUT_CALIBRATION_MATRIX=1.066870 -0.005907 -0.026620 0.007245 -1.136364 1.046200
LIBINPUT_DEVICE_GROUP=3/461/22:usb-ci_hdrc.0-1
MAJOR=13
MINOR=65
SUBSYSTEM=input
USEC_INITIALIZED=514876494495


DEVICE 2:

Touchscreen Hardware on device 2 (reported by xinput):
? Virtual core pointer id=2 [master pointer (3)]
? Virtual core XTEST pointer id=4 [slave pointer (2)]
? Silicon Integrated System Co. SiS HID Touch Controller Mouse id=8 [slave pointer (2)]
? Silicon Integrated System Co. SiS HID Touch Controller Touchscreen id=7 [slave pointer (2)]
? ADS7846 Touchscreen id=9 [slave pointer (2)]
? Virtual core keyboard id=3 [master keyboard (2)]
? Virtual core XTEST keyboard id=5 [slave keyboard (3)]
? 30370000.snvs:snvs-powerkey id=6 [slave keyboard (3)]


/dev/input/touchscreen0 -> /dev/input/event3 (event1 seems like the correct touchscreen though,
based on the udevadm output)


udevadm info --query=property --name=/dev/input/event1
DEVLINKS=/dev/input/by-path/platform-ci_hdrc.0-usb-0:1:1.0-event /dev/input/touchscreen0 /dev/input/by-id/usb-Silicon_Integrated_System_Co._SiS_HID_Touch_Controller-event-if00
DEVNAME=/dev/input/event1
DEVPATH=/devices/soc0/soc/30800000.aips-bus/30b10000.usb/ci_hdrc.0/usb1/1-1/1-1:1.0/0003:04E7:1080.0001/input/input1/event1
ID_BUS=usb
ID_INPUT=1
ID_INPUT_HEIGHT_MM=136
ID_INPUT_TOUCHSCREEN=1
ID_INPUT_WIDTH_MM=215
ID_MODEL=SiS_HID_Touch_Controller
ID_MODEL_ENC=SiSx20HIDx20Touchx20Controller
ID_MODEL_ID=1080
ID_PATH=platform-ci_hdrc.0-usb-0:1:1.0
ID_PATH_TAG=platform-ci_hdrc_0-usb-0_1_1_0
ID_REVISION=0100
ID_SERIAL=Silicon_Integrated_System_Co._SiS_HID_Touch_Controller
ID_TYPE=hid
ID_USB_DRIVER=usbhid
ID_USB_INTERFACES=:030000:
ID_USB_INTERFACE_NUM=00
ID_VENDOR=Silicon_Integrated_System_Co.
ID_VENDOR_ENC=Siliconx20Integratedx20Systemx20Co.
ID_VENDOR_ID=04e7
LIBINPUT_CALIBRATION_MATRIX=1.066870 -0.005907 -0.026620 0.007245 -1.136364 1.046200
LIBINPUT_DEVICE_GROUP=3/4e7/1080:usb-ci_hdrc.0-1
MAJOR=13
MINOR=65
SUBSYSTEM=input
USEC_INITIALIZED=8612683

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