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#1 2021-02-21 20:11:48

JBman100
Member
Registered: 2017-03-15
Posts: 6

Disable tablet support

Hi everyone,

I have a Dell Inspiron 2-in-1 that I would like to use when folded as a keyboard with ports, but the keyboard gets automatically disabled the screen passes a certain point in the rotation.

I would like to understand what triggers it to reverse or disable support for this behaviour. I am not used to debugging things like this and would like pointers as to where to look.

libinput debug-events receives a set of keys when folding (0xf0), but that lead nowhere.
dmesg prints messages from dell-wmi stating an unknown key has been pressed.
xinput does not show anything is disabled when the keyboard is not enabled.

I saw this: https://elixir.bootlin.com/linux/latest … tel-vbtn.c
The kernel module intel_vbtn has functions that detect the tablet mode, but disabling it had no effect. In fact, disabling all dell and intel-hid/isb modules had no effect.

Could something like this be baked in the hardware ? I saw online people saying it could be toggled in windows, but I can't try it as I booted it long ago.

I tried running showkey in tty with the laptop folded, and nothing showed up - this means the issue is not DE related, right ?

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#2 2021-02-21 20:25:28

progandy
Member
Registered: 2012-05-17
Posts: 4,129

Re: Disable tablet support

The switch event is handled by libinput, as far as I know there is no option to override it:
https://wayland.freedesktop.org/libinpu … h-handling

I am not sure which kernel module is responsible for generating the event in your laptop.

Possibly the laptop has disabling logic in hardware as well, but then you'd have to find out how exactly windows can toggle that.

Last edited by progandy (2021-02-21 20:26:22)


| alias CUTF='LANG=en_XX.UTF-8@POSIX ' |

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#3 2021-02-21 21:09:31

JBman100
Member
Registered: 2017-03-15
Posts: 6

Re: Disable tablet support

I saw this, but it does not look like libinput handles the switch, as libinput debug-events does not show the switch while it should: https://gitlab.freedesktop.org/libinput … c#L906-908. Just compiled from source to check the correctness of it.

I just checked that by cat'ting the /dev file of the keyboard, I do not get any input while the keyboard is folded. Can I deduce the keypresses are not handled by the kernel ?

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