Search notes:

/dev/input/eventX

/dev/input/eventX represent event queues.
A /event/dev/eventX «file» is created for each application collection 
$ sudo libinput list-kernel-devices
/dev/input/event0:	AT Translated Set 2 keyboard
/dev/input/event1:	Sleep Button
/dev/input/event2:	Lid Switch
/dev/input/event3:	Power Button
/dev/input/event4:	PC Speaker
/dev/input/event5:	SYNA8004:00 06CB:CD8B Mouse
/dev/input/event6:	TPPS/2 Elan TrackPoint
/dev/input/event7:	LITEON Technology USB Multimedia Keyboard
/dev/input/event8:	USB OPTICAL MOUSE 
/dev/input/event9:	Video Bus
/dev/input/event10:	SYNA8004:00 06CB:CD8B Touchpad
/dev/input/event11:	ThinkPad Extra Buttons
/dev/input/event12:	sof-hda-dsp Mic
/dev/input/event13:	sof-hda-dsp Headphone
/dev/input/event14:	sof-hda-dsp HDMI/DP,pcm=3
/dev/input/event15:	sof-hda-dsp HDMI/DP,pcm=4
/dev/input/event16:	sof-hda-dsp HDMI/DP,pcm=5
Show events fired by mouse actions: 
$ sudo libinput record /dev/input/event8

Device capabilities

The Python library evdev can be used to query an input device's capabilities: 
import evdev

dev = evdev.InputDevice('/dev/input/event7')

caps = dev.capabilities(verbose=True)

for ev in caps:
    print(ev)
    for cap in caps[ev]: 
        print('  ' + str(cap))
#
# ('EV_SYN', 0)
#   ('SYN_REPORT', 0)
#   ('SYN_CONFIG', 1)
#     …
# ('EV_KEY', 1)
#   ('KEY_ESC', 1)
#   ('KEY_1', 2)
#   ('KEY_2', 3)
#    …
#   ('KEY_BACKSPACE', 14)
#   ('KEY_TAB', 15)
#   ('KEY_Q', 16)
#   ('KEY_W', 17)
#   ('KEY_E', 18)
#   ('KEY_R', 19)
#   ('KEY_T', 20)
#    …
# ('EV_MSC', 4)
#   ('MSC_SCAN', 4)
# ('EV_LED', 17)
#   ('LED_NUML', 0)
#   ('LED_CAPSL', 1)
#   ('LED_SCROLLL', 2)

Blinkenlights

The device capabilites for the keyboard reported the three LEDs to indicate Num Lock, Caps Lock and Scroll Lock).
The following Python script randomly turns them on and off: 
import evdev
import time
import random

dev = evdev.InputDevice('/dev/input/event7')

for i in range(20):
    dev.set_led(evdev.ecodes.LED_NUML   , random.choice([0, 1])) 
    dev.set_led(evdev.ecodes.LED_CAPSL  , random.choice([0, 1])) 
    dev.set_led(evdev.ecodes.LED_SCROLLL, random.choice([0, 1])) 
    time.sleep(0.6)

TODO

evemu-…

evemu-describe gathers information about the input device and prints it to stdout. This information can be parsed by evemu-device to create a virtual input device with the same properties.
evemu-record captures events from the input device and prints them to stdout. The events can be parsed by evemu-play to let a virtual input device created with evemu-device emit the exact same event sequence. 
$ sudo evemu-describe /dev/input/event0
$ sudo evemu-describe /dev/input/event8

See also

CONFIG_INPUT_EVDEV is required in order for input events to be accessible under /dev/input/eventX.
The parent directory /dev/input.
Documentation/hid/hidintro.rst

Links

evemu records and replays device descriptions and events, making it possible to emulate input devices through the kernel's input system.

Index