We had this issue for a while, where in lightdm characters would appear in the password input (hidden, so you can't see which ones it actually produces), making it a lot harder to input your password.
Today when trying an older pyra (2gb model), i finally managed to find out which device was causing it (it doesn't happen all the time, and of course when you're looking for it, it doesn't do it).
It seems the pyra-lid-wakeup device causes them, which, after some digging, seem to be connected to wwan_wakeup (line 753+ in pyra-mainboard-v5.0.dtsi)
Why does this device need to produce key events ?
The weird thing is that it only happens when lightdm is running. Running evtest on the device when you're in Xorg, or with lightdm shut down produces no output.
Starting evtest with xorg running shows no events, but after logging out , back the the lightdm login screen, it immediately starts producing these events again.
It seems to happen more on this older 2gb unit than the newer ones, but it still happens occasionally.
evtest output:
Available devices: /dev/input/event0: user-button /dev/input/event1: pyra-game-buttons /dev/input/event2: pyra-lid-wakeup /dev/input/event3: palmas_pwron /dev/input/event4: tca8418 /dev/input/event5: TSC2007 Touchscreen /dev/input/event6: nub0 /dev/input/event7: nub1 /dev/input/event8: accelerometer-iio-input-bridge /dev/input/event9: twl6040:vibrator /dev/input/event10: pyraInput keyboard /dev/input/event11: pyraInput Gamepad /dev/input/event12: pyraInput Mouse Select the device event number [0-12]: 2 Input driver version is 1.0.1 Input device ID: bus 0x19 vendor 0x1 product 0x1 version 0x100 Input device name: "pyra-lid-wakeup" Supported events: Event type 0 (EV_SYN) Event type 1 (EV_KEY) Event code 240 (KEY_UNKNOWN) Event type 5 (EV_SW) Event code 0 (SW_LID) state 1 Properties: Testing ... (interrupt to exit) Event: time 1578938630.370481, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1 Event: time 1578938630.370481, -------------- SYN_REPORT ------------ Event: time 1578938630.382319, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 0 Event: time 1578938630.382319, -------------- SYN_REPORT ------------ Event: time 1578938631.212161, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1 Event: time 1578938631.212161, -------------- SYN_REPORT ------------ Event: time 1578938631.249966, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 0 Event: time 1578938631.249966, -------------- SYN_REPORT ------------ Event: time 1578938631.601427, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1 Event: time 1578938631.601427, -------------- SYN_REPORT ------------ Event: time 1578938631.617213, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 0 Event: time 1578938631.617213, -------------- SYN_REPORT ------------ Event: time 1578938631.732300, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1 Event: time 1578938631.732300, -------------- SYN_REPORT ------------ Event: time 1578938631.776326, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 0 Event: time 1578938631.776326, -------------- SYN_REPORT ------------ Event: time 1578938631.851883, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1 Event: time 1578938631.851883, -------------- SYN_REPORT ------------ Event: time 1578938631.859011, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 0 Event: time 1578938631.859011, -------------- SYN_REPORT ------------ Event: time 1578938632.130892, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1 Event: time 1578938632.130892, -------------- SYN_REPORT ------------ Event: time 1578938632.154042, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 0 Event: time 1578938632.154042, -------------- SYN_REPORT ------------ Event: time 1578938633.093952, type 1 (EV_KEY), code 240 (KEY_UNKNOWN), value 1