Hi guys,

I'm using Arch Linux now for about half a year and it is working like a charm. Seems like I found my distro of choice.
Last week I updated the system and the kernel got updated from 4.17.14 to 4.18.3.
After the next reboot the touchpad of my Lenovo ThinkPad L470 (lsusb defines it as 'Synaptics...') stopped working.

Under the 4.17.14 kernel it worked like it should. Now only 'lsusb' shows the device, 'xinput list' does not anymore.
After manully downgrading the kernel to the previous one, the touchpad works again. So I guess it has to do with the newer kernel.

But now I really dont know where to start with finding a solution for that. I read about compiling a custom kernel or write a dkms module,
but that stuff is brand new to me, so I dont know where to start or even debug the error.

Thanks for ur help

The thing I do to avoid this is use a LTS kernel. While not as "techy" as recompiling the modern kernel with the support for the offending hardware in question, if the LTS kernel supports what I need (it has on all 3 laptops I've had Arch on in the last year), I stick with the LTS kernel.

Good point using a LTS kernel, but not mine. I want to use the leatest and 'greatest'. Do you have any idea why the touchpad does not work under the newer kernel?
Till today I thought, that if a kernel supports some piece of hardware, a newer kernel will do that, too.
Is this wrong, or could it just be a bug?
I want to understand why this happens.

90% of the time it's a regression bug that something was missed. But I got tired enough of it that I don't fight it anymore and I will never run the current kernel anymore in Arch. This happened far too often for me on the current kernel with sound drivers and touchpads.

If you don't mind a lot of hard work, you could do a kernel bisection. I had to do this when I found that kernels later than the 4.13 series wouldn't boot on my machine unless I switched off acpi (which for obvious reasons I was unwilling to do).

What this involves is downloading the kernel git tree (it's about 3 GB) and running git bisect on it repeatedly. You need to start with two known endpoints: a kernel that definitely works and one that definitely doesn't, as close to each other as possible. Each bisection gives you a new halfway kernel to build and test. Eventually you find the change that caused the problem. Then you can write a patch to reverse it.

Curiously the problem in my case turned out to be a change in the way memory was mapped. But it was a function in the acpi driver that triggered it.

have you checked if the touchpad works better with libinput or synaptics?
https://wiki.archlinux.org/index.php/Touchpad#Touchpad
this suggests that libinput should be preferred, but maybe you would benefit from synaptics.
who knows.
honestly, from an archlinux user i would expect much, much more output and troubleshooting information.
all you are saying is, basically, that the touchpad doesn't work after a kernel upgrade...
your arch forums thread was likely met with stony silence.

why?
it's not "greater" just because it's newer (as you are experiencing right now), and your laptop isn't getting any newer either.

you could try skipping this one kernel upgrade and see if it gets better after the next.
not a biggie for an archlinux user.

1 members found this post helpful.

Moved: This thread is more suitable in <Arch> and has been moved accordingly to help your thread/question get the exposure it deserves.

Update 4.19.1

Still not working.

bumping a thread without providing new information is usually frowned upon; certainly by me, esp. since you still haven't reacted on my suggestion of trying synaptics instead of libinput, and haven't actually shown us any effort/output.

@xdyz5mx6


From LQ Rules I do suggest that you re-read LQ Rules so you can insure that rules are followed.

I think OP was saying updated kernel to 4.19.1 and still not working.
@ xdyz5mx6 - Have you tried hazel's suggestion in #5? or ondoho's in #6? or looked for any related bug report in Arch?

Hi xdyz5mx6,

Please see ondoho's above post #6. The last time I had a touchpad / pointing device issue after a kernel update on one of my Arch systems, it had to do with the libinput vs. synaptics issue. For that particular system, the solution was to switch to synaptics. In other cases, it was necessary to edit the appropriate conf file and make sure the evdev driver was specified ... Could be various things.

It is fairly simple to fix once you zero in on the specific cause, which may vary depending on your hardware.

Investigate along this path and let us know how you make out.

Cheers.