What is phy0-led?

I’ve got four entries in /sys/class/leds:

  • input0::capslock
  • input0::numlock
  • input0::scrolllock
  • phy0-led

input0 is the keyboard, but what is phy0-led? Writing to its brightness doesn’t seem to change anything (aside from the value in the file), but it looks like it always starts at 1. Unfortunately it isn’t the power button.

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Resolving the symlink shows the actual path of the LED puts it under the WiFi card’s PCI device:

$ pwd -P
/sys/devices/pci0000:00/0000:00:1d.0/0000:aa:00.0/leds/phy0-led

Maybe it’s the network activity LED, that just goes nowhere because the framework doesn’t have one.

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