First check you have the timer trigger loaded:
root@gimli:~# lsmod |grep led
snd_ctl_led 24576 0
input_leds 16384 0
snd 135168 45 snd_ctl_led,snd_hda_codec_generic,snd_seq,snd_seq_device,snd_hda_codec_hdmi,snd_hwdep,snd_hda_intel,snd_usb_audio,snd_usbmidi_lib,snd_hda_codec,snd_hda_codec_realtek,snd_sof,snd_timer,snd_compress,thinkpad_acpi,snd_soc_core,snd_pcm,snd_rawmidi
soundcore 16384 2 snd_ctl_led,snd
ledtrig_audio 16384 3 snd_ctl_led,snd_hda_codec_generic,thinkpad_acpi
It wasn't loaded, so modprobe it:
root@gimli:~# modprobe ledtrig-timer
Now you can see it in the list of available triggers for you LED:
root@gimli:~# cat /sys/class/leds/input4\:\:capslock/trigger |grep timer
[none] usb-gadget usb-host rfkill-any rfkill-none kbd-scrolllock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock kbd-ctrlllock kbd-ctrlrlock timer
We'll use your CapsLock LED in this example. So let's first turn
that LED on. ON or OFF can mean 1 and 0 but may also be 255
and 0. It all depends on the driver, see max_brigtness for the
maximum (full brightness) for each LED.
root@gimli:~# echo 1 > /sys/class/leds/input4\:\:capslock/brightness
It should now be ON. Time to try blinking, set the timer trigger:
root@gimli:~# echo "timer" > /sys/class/leds/input4\:\:capslock/trigger
The default is to blink at 1 Hz, off 500 ms, then on 500 ms. This
can be adjusted with delay_off and delay_on, which appear when
you set the timer trigger:
root@gimli:~# ls /sys/class/leds/input4\:\:capslock/
brightness delay_off delay_on device/ max_brightness power/ subsystem/ trigger uevent
Let's blink it quicker!
root@gimli:~# echo "100" > /sys/class/leds/input4\:\:capslock/delay_off
root@gimli:~# echo "100" > /sys/class/leds/input4\:\:capslock/delay_on
wow that's quick!
Turn off blinking, and disable the timer trigger, by:
root@gimli:~# echo 0 > /sys/class/leds/input4\:\:capslock/brightness