Keyboard backlight control missing on later CAROLINE

Bug Reports Firmware Bugs
1

Hey. I have a Samsung Chromebook Pro (CAROLINE), and it has a keyboard backlight, but it appears that you cannot manually change the brightness via the OS (Linux distro or Windows).
This is a continuation of the support I received thru Discord on 13 November, 2023.

Here’s some context (tl;dr):

  1. KB backlight can be manually set with ectool; cannot be changed via OS GUI or key sequence (Modifier + +/- Brightness).
  2. Issue occurs regardless of the distro or OS of choice (Ubuntu, Debian, Fedora, Windows).
  3. CAROLINE originally didn’t have a keyboard backlight. Samsung later released new model with KB backlight.
  4. coreboot may not have acpi enabled for keyboard backlight for CAROLINE?[1][2]

I have made this topic to hopefully shed some more light on the problem. Would adding support for CAROLINE keyboard backlight be feasible, or would it cause issues for older models? I’m happy to provide any more debug or device info at request.

  1. weirdtreething on chrultrabook Discord ↩︎

  2. weirdtreething on chrultrabook Discord ↩︎

2

CAROLINE does not have the EC_ENABLE_KEYBOARD_BACKLIGHT set, it would need to be added for coreboot to provide the OS interface for controlling the backlight level.

3

Thanks for the info! I (somehow) managed to compile my own firmware rom for my CAROLINE device, defining the EC_ENABLE_KEYBOARD_BACKLIGHT, and OS keyboard backlight control seems to work flawlessly.
To clarify one of my prior questions, would including this change in an official coreboot release introduce any compatibility issues with older CAROLINE devices? (not that it would affect me, I’m just curious)

4

I’ll be adding it to a future release, no issue other than same similar models have – if there’s no kb backlight hardware, the OS control won’t do anything

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