There are many pages here with scipts, but I haven't found one explaining just "what to put where" to make LED's on. This is a short summary of what I've found out (fw v2.00.18):

The key folder is /sys/class/leds/

It containts some subfolders:


each of which containts subfolders:


device is a symlink to ../../../devices/platform/wdc-leds
I haven't already found, what are trigger and uevent - there is a place for all of you to research (:
But the whole fun is with brightness file (:
Just echo something to it and watch reaction of leds. (for example: echo 63 > /sys/class/leds/wdc-leds:fg-bitmap/brightness should light the whole inner ring. Why? I'll explain (; ).

There are 4 leds at the outer ring (I'll call them N, S, W, E) and 6 leds at the inner ring.

[folder] [value] effect of echo [value] > /sys/class/leds/wdc-leds:[folder]/brightness
ignore-act 1 turns on ignoring activity mode - outer ring stays on, even when the disk is active. When it's on putting something to activity/brightness is pointless
ignore-act 0 turns off ignoring activity mode
activity 1 turns outer ring S led on, after a while it slowly dims. Called once again do so with W led, next call plays with N led, another with E led, next with S and so on
transition 1 plays transition animation once
over-temp 1 turns on over-temp animation (blinking of all leds) and keeps playing it
over-temp 0 turns off over-temp animation, then plays transition animation once
degraded 1 turns on degraded animation (interchanging blinking of inner and outer ring) and keeps playing it
degraded 0 turns off degraded animation, then plays transition animation once
power 0 plays transition, then turns off all leds. They could be on for example by playing transition animation
power 1 if leds are on, then it plays transition and turns them off. Than it keeps slowly blinking outer ring. Inner ring is than repainted only while the outer ring is on
fg-bitmap 6-bit value full controll of fuel gauge - just put a 6-bit value, each bit is for one led (:
fuel-gauge - why need something more when you have fg-bitmap?*
rebuilding - sad to say, but I can see no influence on leds ):

*A matter of fact I can't see any influence of putting something there. Maybe it's because of new firmware (2.00.18)? Some explanation can be found here: http://mybookworld.wikidot.com/forum/t-28326/mbwe-led-control
**[TINOBRUNO] i got it… the fuel-gauge stream accepts PERCENTAGE values… so you can completely light the inner ring just sending 100… or half the ring sending 50… clear enough? i think it's easier than using fg-bitmap in some circumstance…

Hope that helps (: And hope someone will find something more than this! Still controll of the outer ring is only high-level… But inner is fully yours! (God bless fg-bitmap! (; )

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