LED use, customization ?

[Lousy Fisherman]

Is there a way to use LEDs?  Ideally, would be nice to customize them for various uses.  As a minimum, I'd like to have a LED notification whenever I have a missed call or a new message (sms, email).  Also a LED battery charging indicator is useful.  Would be great if a user can specify in settings or some config file color, duration, pattern of the LED notification.  At present, my LEDs are off all the time - am I missing something?

Megi's LED info is interesting, but not for layman's practical use.

BTW, it was pleasant to experience use of LEDs by sxmo.

Cheers for the link, hadn't found that on Megi's site. Yup on Arch there are none activated by default but pretty easy to activate - I am not that good with permissions so just do a sudo su to get enough power.

Seems with the 5.9.11 kernel the /sys/class/leds layout has changed slightly - I now have

Code:

# echo mmc2 > '/sys/class/leds/blue:indicator/trigger'

For sure there must be some way to trigger on email etc notification as Mobian was doing it last time I looked, but not obvious to me from the 5.9.11 options:

Code:

$ cat '/sys/class/leds/blue:indicator/trigger'
[none] 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 heartbeat cpu cpu0 cpu1 cpu2 cpu3 default-on panic pattern axp20x-battery-charging-or-full axp20x-battery-charging axp20x-battery-full axp20x-battery-charging-blink-full-solid axp20x-usb-online rfkill0 mmc0 mmc1 mmc2 rfkill1 bluetooth-power hci0-power rfkill2

Thanks to both of you. I was not looking for this information yet, but I knew I needed it. 
LF