Everybody uses at least one input device when dealing with a computer. And hopefully, this input device “just” works. However, when dealing with the brand-new latest laptop model, it’s common enough that the input devices are not working, or are not working as expected by the users. The reasons are manifold: OEMs want to have more power efficient laptops and are generally refusing to use well-tested PS/2 ball mice from 15 years ago. So they are introducing new touchpads using weird communication protocols. Or they simply want to introduce brand new types of interaction with their laptops (think the latest Macbook Pro and their function bar, but Lenovo had something equivalent 3 years ago on their X1 Carbon). Alongside new devices came the development of Wayland. The end result is that the input stack has evolved a lot in the past few years, and it’s a good thing to give an update of it. In this talk, we will present what work has been conducted throughout the whole input stack, from the kernel to toolkits (with an emphasize on the kernel). We will explain the choices we made, and why the plans don’t always work. After an overview of the full input stack in current distributions, we will outline the development efforts to support the various device types (mice, touchpads, touchscreens, etc.). Of course, we will tell you the most crusty problems we had to face because who doesn’t like a nice anecdote about hardware oddities. We hope to make a pleasant talk where no requirements is necessary. We also hope attendees will learn how the input stack is structured. And of course, we hope the attendees will have a more compassionate eye regarding their preferred mouse, touchpad, keyboard or any other device, thinking of the dedication we put in to make their life easier (one can always hope). Benjamin Tissoire, Red Hat

1. What's inside the input stack?
🐁
Kernel Recipes 2017

2. About me:
Benjamin Tissoires (irc: bentiss)
• Software engineer at Red Hat
• kernel hid-multitouch maintainer, hid core
co-maintainer
• also gives bad advice for the upper input stack

3. About the other guy:
Peter Hutterer (irc: whot)
• Software engineer at Red Hat
• libinput maintainer
• Maintainer of the X.Org input stack, and evdev,
synaptics, ... drivers
• (99% of the time, 'we' means him and I)

4. Isn't it working already?

6. Problem is:
hardware makers can be creative

9. And usage is changing

11. Outline:
• Introduction
• Input architecture
• Talking about a bunch of devices
• A little bit about security

12. Everything you never wanted to
know about 'how input works'

13. Components:
• Kernel
• libinput
• "Wayland" or Xorg
• toolkit
• application

14. Kernel:
• knows about protocols (HID, RMI4, ...)
• knows about transport layer (USB, PS/2,
SMBus, I2C, etc...)
• talks evdev

15. Libinput:
• because input is "easy"
• relies on libevdev
• does fancy things like gestures
• has a global view of the input devices

16. Compositor (or Xorg):
• loads libinput
• pass incoming events to the right client

17. Toolkits:
• relies on [see previous slides]
• does fancy things like gestures too

18. Applications:
• do something useful (hopefully)

19. The good, the bad and the ugly
(of input devices)

20. Keyboards

21. Page left blank

22. Actually no...
the Caps Lock LED in a TTY is
broken since UTF-8 support in
the kernel

23. Actually no...
the Caps Lock LED in a TTY is
broken since UTF-8 support in
the kernel
pro tip: add /etc/udev/rules.d/99-kbd.rules
ACTION=="add",
SUBSYSTEM=="leds",
ENV{DEVPATH}=="*/input*::capslock",
ATTR{trigger}="kbd-ctrlllock"

24. Mice

25. (for the kernel)
Not much to add...
.

26. (for the kernel)
Not much to add...
except libratbag

27. libratbag:
A thing to configure gaming mice
• fun project to hack on
• allows for reverse engineering without
the pain of breaking the kernel
• supports many gaming devices:
Logitech, Roccat, G-Skill, Razer (in progress)

28. Touchpads

29. Most are still using PS/2

30. story time: T440

31. story time: T440

32. story time: T450

33. story time: T450

34. A little bit about security
(with a red background)

35. CVEs?:
• yes, but only a few
• one notable was regarding the ChromeBook injecting
HID event through a web application

36. MouseJack

37. MouseJack:
Congrats, your mouse is IoT ready!
http://www.mousejack.com/
.

38. MouseJack:
Congrats, your mouse is IoT ready!
http://www.mousejack.com/
You have to update it

39. Summary:
• Input architecture
• some devices still need some care
• security is also involved

40. Credits
• PS/2 keyboard: CC BY Matthijs Kooijman
• G600 Gaming Mouse: all rights reserved, Logitech
• Lenovo X1 Carbon: CC BY-SA 2.0 Stannate
• Lenovo Yoga Tablet 3 Pro: all rights reserved, Lenovo

41. Thanks!
benjamin.tissoires@(gmail|redhat).com
IRC: bentiss @freenode @gimpnet

42. Summary:
• Input architecture
• some devices still need some care
• security is also involved