Laptop keyboard skipping key down events

novakk · 2025-01-08 12:48:18

Hi everyone.

When i hold down multiple keys and then try to input the middle row of the keyboard, i.e. the t, y, g and h keys the input is not registered.
Also when i try to input multiple keys at the exact same time, for example the d, f, j and k keys, it sometimes causes the inputs to drop.
Could this be caused by a software issue or is this just an issue with my hardware builtin keyboard? Plugging in an external one works perfectly fine.
I've already tried looking for atkbd alternatives, but couldn't find any.

If you require any logs ill reply asap, thanks in advance.

V1del · 2025-01-08 13:51:29

Normally HW limitation, cheaper keyboards only allow a certain combination of simultaneously pressed keys, depending on how they are wired up. It's usually a selling point of keyboards to explicitly mention how many keys they can press at the same time (look into N-key rollover and similar) e.g. https://en.wikipedia.org/wiki/Key_rollover

Last edited by V1del (2025-01-08 13:53:33)

novakk · 2025-01-08 14:36:57

I wouldnt mind having 6KRO The problem is that the keyboard behaves really inconsistently, for example when i press multiple buttons at the same time they dont register at all. And also the fact that holding down keys disbles rhe middle row of the keyboard for some reason.

I can make a video showcasing the issue or dualboot into windows to test it there, but im almost sure that the issue would dissapear.

V1del · 2025-01-08 14:53:14

I'm almost sure the issue would remain. If you're KRO limited (6 is also just a number might be less if you're unlucky, e.g. 3 is also not uncommon) it's not necessarily deterministic which exact keys don't work in combination that really depends on the internal layout . Your symptom description very much sounds like KRO in effect. Generally speaking I'm not aware of anything of this getting limited in software, it's almost certainly HW (especially since external keyboards work, if you ran into a software limit, the external keyboard would exhibit the same issue). What exact laptop model?

Fun anecdote, I used to play Smash Bros with a few mates on a single computer during school breaks and the keyboard there was at most 3KRO, it was very easy to fuck up someones recovery by just pressing multiple keys, which was often used to the detriment of the other player

Assuming it is indeed in software, is a certain client affected? Can you reproduce the drop in xev (then the xorg layer would be affected) or in libinput debug-events (if there then it's either kernel or HW)

Last edited by V1del (2025-01-08 14:56:18)

novakk · 2025-01-08 15:01:56

Tested it on gnome-xorg gnome-wayland and openbox, same thing everywhere. The laptop is quite new as its a zenbook 14 oled

Ill make a video showing the issue and post it here

V1del · 2025-01-08 15:10:46

The newness is irrelevant, vendors are still going to make laptops that don't have proper rollover, it's a matter of cost and it's cheaper to make keyboards without n-key rollover.

All of these are logically the same layer safe for gnome-wayland but using sudo libinput debug-events will show you what happens on the kernel level, if they don't show up there, they don't show up anywhere. Maybe check the LTS kernel or so, I could see some interference with the asus_wmi module, but I'd not keep my hopes high. The best test would be checking on Windows or so.

seth · 2025-01-08 15:35:51

You want to check whether the keys get registered by "evtest" - if not, a software issue is unlikely (resp. would hint at a kernel module, eg. specific WMI)

Next to nkro, don't underestimate boring mechanics - notably tension on the keyboard.
Can you eg. register parallel q-p-x-m (ie. at the corners)

novakk · 2025-01-08 19:50:34

Even evtest doesn't pick up the keys.
Here is a video showcasing the issue (simillar thing on evtest): https://youtu.be/xPZe4cTnKfk

I noticed on a different laptop with windows installed that when pressing multiple buttons at the same time, instead of not inputting at all they just delay a frame.
I also tested the corners and they all work.

seth · 2025-01-08 20:45:05

I also tested the corners and they all work.

Going with the theory of a mechnical problem, you'd have to dismount the keyboard from the frame, back it with something hard (but not conductive, eg. cardboard - not an aluminium sheet) and see whether it now behaves differently. Pressing four keys very much at the center is prone to bend it inwards and if it's under tension it'll bend in there the most anyway.

"Different laptop" is still "same model"?
Otherwise that's really not relevant at all.

novakk · 2025-01-08 20:49:28

I dont think the issue is mechanical as ive said, the laptop is literally half a month old and even if it is a mechanical issue i really dont feel any bend on the keyboard.
The last thing i can try to do is boot into windows and try there.

seth · 2025-01-08 20:57:32

Age doesn't have much to do with a bad fit, feel free to test the behavior on windows but please see the 3rd link below. Mandatory.
Disable it (it's NOT the BIOS setting!) and reboot windows and linux twice for voodo reasons.

Arch Linux

#1 2025-01-08 12:48:18

Laptop keyboard skipping key down events

#2 2025-01-08 13:51:29

Re: Laptop keyboard skipping key down events

#3 2025-01-08 14:36:57

Re: Laptop keyboard skipping key down events

#4 2025-01-08 14:53:14

Re: Laptop keyboard skipping key down events

#5 2025-01-08 15:01:56

Re: Laptop keyboard skipping key down events

#6 2025-01-08 15:10:46

Re: Laptop keyboard skipping key down events

#7 2025-01-08 15:35:51

Re: Laptop keyboard skipping key down events

#8 2025-01-08 19:50:34

Re: Laptop keyboard skipping key down events

#9 2025-01-08 20:45:05

Re: Laptop keyboard skipping key down events

#10 2025-01-08 20:49:28

Re: Laptop keyboard skipping key down events

#11 2025-01-08 20:57:32

Re: Laptop keyboard skipping key down events

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