[Bug 221583] Lenovo 82KU: keyboard backlight works via Fn+Space but no kbd_backlight LED device exposed

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=221583

--- Comment #26 from George (george.stafilidis@proton.me) ---
Hi Rong,

I did the lid test exactly as you asked. I set the keyboard brightness to High
using Fn+Space. When I closed the lid, the keyboard light turned off after
about 5 seconds. When I opened the lid again, the light turned back on at High.
(Closing the lid when the keyboard light is off does not turn it open when i
open the lid)

I also ran the diff command on the MMIO dumps before closing and after opening
the lid. The output is:
2c2
< 0x00000000FE00D401: 00010000
---
> 0x00000000FE00D401: 00000001

7c7
< 0x00000000FE00D406: 00011100
---
> 0x00000000FE00D406: 00011010

177,178c177,178
< 0x00000000FE00D4B0: 00110010
< 0x00000000FE00D4B1: 00101100
---
> 0x00000000FE00D4B0: 00100110
> 0x00000000FE00D4B1: 00101010

184c184
< 0x00000000FE00D4B7: 00101000
---
> 0x00000000FE00D4B7: 00100111

199c199
< 0x00000000FE00D4C6: 00010010
---
> 0x00000000FE00D4C6: 00010011

I also did the manual test of register 0x8A as yoy asked

Step 3 (KBLO = 0, KLFS = 0): the light turned OFF
Step 4 (KBLO = 0, KLFS = 1): the light did not turn ON
Step 5 (KBLO = 1, KLFS = 0): the light turns ON at LOW brightness
Step 6 (KBLO = 1, KLFS = 1): the light stays at LOW brightness

Hopefully i got everything correct. I am also attaching the stock dsdt.

Oh  yeah also Bios info:
Version: GLCN68WW
Release Date: 03/19/2025

Have a wonderful night!

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