How to change a keycode using setkeycodes

Question

I have a Thinkpad Edge E130 running Sabayon (a Gentoo-based distro), and I'm fighting the well-know bug Xorg 255 keycodes limit.

My laptop has the Fn+F4 hotkey for Mic Mute/Unmute. This is the problem:

showkey -k shows keycode 248 on Fn+F4 keypress
showkey -s shows nothing on keypress
xev shows nothing on keypress (because 248+8 [added by kernel] is bigger than 255)

If a key has a keycode, it must have a scancode too. With getscancodes program indeed I got 26 as scancode:

# ./Sabayon/getscancodes/getscancodes /dev/input/event6 
Input driver version is 1.0.1
Input device ID: bus 0x19 vendor 0x17aa product 0x5054 version 0x4101
Input device name: "ThinkPad Extra Buttons"
26 (0x1a)
26 (0x1a)

According to this thread, my guess is simply to change the keycode of the hotkey with a smaller, unused one. For example 120 seems to be unused according to my $ xmodmap -pke

I have tried with

# setkeycodes 0x1a 120

but without success, the keycode is always 248 checking with showkey.

How is the proper way to change keycodes?

score 4 · Answer 1 · edited Sep 24 '14 at 21:42

4

Use showkey to know your key scancode:
```
$ sudo showkey -s
0xe0 0xXX
```
Kernel will add 8 to you code, use 112 instead 120:
```
$ sudo setkeycodes e0XX 112
```
Use xmodmap to make your key report XF86AudioMute keysym:
```
$ xmodmap -e "keycode 120 = XF86AudioMute"
```
Optional. Press you key when creating shortcut to what you want in the settings of your DE.

edited Sep 24 '14 at 21:42

HalosGhost

4,790

answered Sep 24 '14 at 21:39

user780773

41

Actually I switched to Debian Sid and Fn+F4 works out of the box here (maybe just because I have a newer kernel version). But thank you anyway, your solution looks good and I hope will help other people. – eang Sep 26 '14 at 08:47
2

This does not work for USB keyboards, because setkeycodes does not support them. If the system has udev, the keys can be remapped by adding a custom entry to the hardware database. Example here: https://unix.stackexchange.com/a/384566/245377 – user3096626 Aug 08 '17 at 13:01
Why subtract 8? Do you have chapter and verse? – Tom Hale Sep 02 '19 at 12:42
Note if you are trying to use showkey -s: it may not report real raw scancodes for use with setkeycodes; as a sanity check, compare the resulting keycodes (shown by showkey [-k]) with what keycode the table for the existing mapping shown by getkeycodes says should be produced for the scancode you got from showkey -s. – rakslice Jan 15 '20 at 22:29
How to get the scancode if sudo showkey -s doesn't return anything? I'm also in the same scenario, showkey -k returns 248 for me. – Utkarsh Verma Apr 27 '20 at 13:17

score 1 · Answer 2 · answered Jan 05 '21 at 22:09

What I want to do is that when the "pause" button is pressed, the character "k" is printed. The problem is that the "pause" button has no scan code (showkey -s does not work). I solved this problem like this:

Switch to the console
Use showkey -k to know keycode of "pause" button (425 in my case)

$ showkey -k
keycode 425 press
keycode 425 release

Use getkeycodes to get a table of mapping keycodes to scancodes

e0 68:  128 159 158 157 155 226 225 224
e0 70:    0 192 193 149 148 425 116   0
e0 78:  464 148   0   0   0   0   0   0

In this table find the scancode associated with keycode 425 (e075 in my case)
Switch back to X
Use xmodmap -pke to find keycode you need (you can also modify them) (45 in my case)

keycode  45 = k K Cyrillic_el Cyrillic_EL k K

Subtract 8 to get kernel keycode (45 - 8 = 37)
Use setkeycodes to add association between raw scancode e075 and kernel keycode 37

sudo setkeycodes e075 37

Test it. It should work

score 0 · Answer 3 · edited Apr 05 '19 at 22:26

0

step 1: xmodmap -pke will list you keycodes

step 2: xmodmap -e 'keycode 51 = backslash bar' will change that keycode to backslash

edited Apr 05 '19 at 22:26

Rui F Ribeiro

56,709
26
150
232

answered Oct 02 '16 at 11:43

Nick

11

How to change a keycode using setkeycodes

3 Answers3

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