Disabling Raspberry Pi Power LED

I’m trying to figure out how to toggle the main red power light on a Raspberry Pi.

On a non-NixOS system, I’d run echo none | sudo tee /sys/class/leds/led1/trigger, and revert that with echo default-on | sudo tee /sys/class/leds/led1/trigger. But on my NixOS Pi, the only LEDs I can find are /sys/class/leds/mmc1:: and /sys/class/leds/ACT, neither of which seem to correspond to the one I’m trying to manipulate.

FWIW, the NixOS device is a RPi3, while the other I’m testing with is a RPi4, but I’d be surprised if that was what’s making the difference.

I also just noticed that disabling /sys/class/leds/mmc1:: has no visible effect at all as far as I can tell.

this may help you, Seems to be different on the pi3 vs the pi4

then again it might not.

Thanks, that was helpful.

In particular, this comment looks promising, but ./rpi3-gpiovirtbuf c 135 1 0 0 0 0 fails with error: open: /dev/vcio: No such file or directory. Might that functionality exist at a different location on NixOS?

You may need to use the rpi kernel instead of mainline.

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That sounds reasonable. I added boot.kernelPackages = pkgs.linuxPackages_rpi3 to my config (along with this workaround.

But it doesn’t boot! Some text is printed, than I eventually get a black screen and the heartbeat LED turns off. The text moves too quickly for me to see what happens at the end, and I can’t find any way to access the log after the fact.

I’ve reverted back to the old config for now, but I would really love to get this working.