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[Resolved] No "netdev" trigger option for network LED



Hi all.

Some time ago, in the release notes of a past Armbian version, I remember reading that the network LED should now be enabled by default and associated with eth0.

Despite always keeping my Helios64 as up-to-date as possible, mine never lit up, but I didn't think much of it. Today I decided to investigate why, and I'm not sure where to go from here.


First things first, the LED works, it's not a hardware issue. I can echo 1 and 0 to the LED path (/sys/class/leds/helios64:blue:net/brightness) and it lights on and off as expected.


From what I can tell, this LED, along with the heartbeat one, is enabled by the Systemd unit helios64-heartbeat-led.service. When I check for the status of the unit, I get the following output:

● helios64-heartbeat-led.service - Enable heartbeat & network activity led on Helios64
   Loaded: loaded (/etc/systemd/system/helios64-heartbeat-led.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sat 2021-03-13 00:30:52 GMT; 8min ago
  Process: 3740 ExecStart=/usr/bin/bash -c echo heartbeat | tee /sys/class/leds/helios64\:\:status/trigger (code=exited, status=0/SUCCESS)
  Process: 3744 ExecStart=/usr/bin/bash -c echo netdev | tee /sys/class/leds/helios64\:blue\:net/trigger (code=exited, status=1/FAILURE)
 Main PID: 3744 (code=exited, status=1/FAILURE)

Mar 13 00:30:52 nas.lan systemd[1]: Starting Enable heartbeat & network activity led on Helios64...
Mar 13 00:30:52 nas.lan bash[3740]: heartbeat
Mar 13 00:30:52 nas.lan bash[3744]: netdev
Mar 13 00:30:52 nas.lan bash[3744]: tee: '/sys/class/leds/helios64:blue:net/trigger': Invalid argument
Mar 13 00:30:52 nas.lan systemd[1]: helios64-heartbeat-led.service: Main process exited, code=exited, status=1/FAILURE
Mar 13 00:30:52 nas.lan systemd[1]: helios64-heartbeat-led.service: Failed with result 'exit-code'.
Mar 13 00:30:52 nas.lan systemd[1]: Failed to start Enable heartbeat & network activity led on Helios64.


Looking into the unit's source, I can see the line where this fails:

ExecStart=bash -c 'echo netdev | tee /sys/class/leds/helios64\\:blue\\:net/trigger'


And sure enough, there is no "netdev" inside /sys/class/leds/helios64:blue:net/trigger:

$ cat /sys/class/leds/helios64:blue:net/trigger
[none] usb-gadget usb-host kbd-scrolllock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock usbport mmc1 mmc2 disk-activity disk-read disk-write ide-disk mtd nand-disk heartbeat cpu cpu0 cpu1 cpu2 cpu3 cpu4 cpu5 activity default-on panic stmmac-0:00:link stmmac-0:00:1Gbps stmmac-0:00:100Mbps stmmac-0:00:10Mbps rc-feedback gpio-charger-online tcpm-source-psy-4-0022-online


I'm not sure why it's not there or how does that get populated.

I'm running Armbian Buster 21.02.3 with LK 5.10.21-rockchip64. Any help will be much appreciated.

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So, I went hunting for the PR where this got merged, found the reference to kernel module "ledtrig-netdev", noticed the module wasn't loaded on my Helios 64 (no idea why), loaded it via modprobe, restarted the service unit I mentioned in the post above, and now it works.

I've added ledtrig-netdev to /etc/modules-load.d/modules.conf, so now it should hopefully work automagically on every boot.

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