Arch Linux

boarim

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Registered: 2022-05-28

Posts: 16

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Hardware button for radio killswitch has inconsistent behavior

Running osboot and Arch on ThinkPad T400s here.

The laptop has a radio killswitch on the side of its case. However, I cannot use it to its full extent because of its inconsistent behavior.

I tested with different scenarios to get as much information as possible. Here are the different output of the rfkill command:

Button ON

The killswitch is set to the ON position from startup.

ID TYPE      DEVICE                   SOFT      HARD
 0 bluetooth tpacpi_bluetooth_sw unblocked unblocked
 1 wwan      tpacpi_wwan_sw        blocked unblocked
 2 wlan      phy0                unblocked unblocked
 4 bluetooth hci0                unblocked unblocked

Button OFF

Then, I switched it to OFF to kill all radio devices.

ID TYPE      DEVICE                   SOFT      HARD
 0 bluetooth tpacpi_bluetooth_sw unblocked unblocked
 1 wwan      tpacpi_wwan_sw        blocked unblocked
 2 wlan      phy0                unblocked unblocked

It only works for the Bluetooth card (although it is not registered by rfkill in the HARD column).

Button OFF from startup

This time, I switched it to OFF from the startup.

ID TYPE      DEVICE                 SOFT      HARD
 0 bluetooth tpacpi_bluetooth_sw blocked   blocked
 1 wwan      tpacpi_wwan_sw      blocked   blocked
 2 wlan      phy0                blocked unblocked

It works, although it set a software block for the WLAN card instead of a hardware one. However, even if I change the button position afterwards, nothing changes. I have to reboot the laptop to make Arch acknowledges the new killswitch position.

So, it seems the BIOS registers the position, but once the OS is started, the killswitch has little to no effect.

In which direction should I look to pinpoint the root cause?

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Simplicity is the ultimate sophistication. — Leonardo da Vinci (1452–1519)