[Bug 216150] New: ideapad-laptop exposes only two keyboard backlight levels, instead of three

[Bug 216150] New: ideapad-laptop exposes only two keyboard backlight levels, instead of three

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=216150

            Bug ID: 216150
           Summary: ideapad-laptop exposes only two keyboard backlight
                    levels, instead of three
           Product: Drivers
           Version: 2.5
    Kernel Version: 5.18.1
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Platform_x86
          Assignee: drivers_platform_x86@kernel-bugs.osdl.org
          Reporter: tinozzo123@tutanota.com
        Regression: No

I own a Lenovo IdeaPad 5 14ARE05, which has three keyboard brightness levels:
off, low and high, which are cycled through with the Fn+space key combo.
However, ideapad-laptop.c sets max_brightness to 1, which means that the
brightness is either off (0) or on (1). This means that I'm unable to select
the high intensity brightness from ACPI like I could on a ThinkPad (I don't own
one, but thinkpad_acpi.c sets max_brightness to 2, so I guess that it doesn't
have that problem).


Still, I don't know if this feature is present on all IdeaPad laptops. I
couldn't find any documentation on this (there is an article on Lenovo's
support, but it only refers to ThinkPads*). Even the user manual of my laptop
doesn't mention this (it only says that it has keyboard backlight, not that it
has three levels). Finally, I never tested Windows, so I don't know if Lenovo
Vantage provides any more settings.

Also, small note: right now, if the keyboard brightness is at high intensity
(with Fn+space, since there is no other way to do it), then is set to 0 using
ACPI (and *not* with Fn+space), then set to 1 again with ACPI (still *not* with
Fn+space), the result is that the keyboard backlight will turn on with high
intensity (and the next Fn+space will turn it off) instead of low.

*https://support.lenovo.com/us/en/solutions/ht104451-how-to-turn-onoff-the-keyboard-light-backlit-on-your-laptop-thinkpad

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[Bug 216150] ideapad-laptop exposes only two keyboard backlight levels, instead of three

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=216150

Barnabás Pőcze (pobrn@protonmail.com) changed:

           What    |Removed                     |Added
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                 CC|                            |pobrn@protonmail.com

--- Comment #1 from Barnabás Pőcze (pobrn@protonmail.com) ---
From https://bugzilla.redhat.com/show_bug.cgi?id=1979909:

> Hi
> 
> This is a limitation of the interface. The device I tested this feature on
> also has three keyboard backlight levels that can be changed using Fn+space,
> however, the Lenovo Vantage software on Windows can only turn it on/off,
> because the that's all the interface is capable of. And since I based my work
> on that, this limitation is carried over to the Linux kernel driver. If I
> recall correctly there is another interface that has multiple backlight
> levels, but my device was not compatible so I didn't attempt to implement
> that. Curiously, the backlight change notification is still sent.

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