Public bug reported:
On my Lenovo ThinkPad L13 Yoga Gen 2a (model 21AES01A00), the keyboard
backlight is not detected on Linux kernel 7.x.
The keyboard backlight works correctly on kernels 6.8 and 6.9 (e.g., Linux
Mint), where /sys/class/leds/tpacpi::kbd_backlight is present.
On kernel 7.x, the LED interface is missing entirely.
Expected behavior:
thinkpad_acpi should detect the keyboard backlight and expose the LED interface
tpacpi::kbd_backlight.
Actual behavior:
The keyboard backlight is not detected.
The Fn+Space key does nothing.
There is no LED entry for the keyboard backlight under /sys/class/leds/.
thinkpad_acpi prints the following messages when loading:
thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control,
supported by the ACPI video driver
thinkpad_acpi: Standard ACPI backlight interface available, not loading native
one
This is incorrect:
The ThinkPad L13 Yoga Gen 2a does have a native ThinkPad keyboard backlight,
and it works on older kernels.
Hardware:
Lenovo ThinkPad L13 Yoga Gen 2a
Model: 21AES01A00
BIOS: R1QET52W (1.38)
EC: R1QHT32W
Kernel version:
7.0.0-15-generic (Ubuntu 26.04)
Relevant dmesg output:
[ 15.265890] thinkpad_acpi: This ThinkPad has standard ACPI backlight
brightness control, supported by the ACPI video driver
[ 15.265892] thinkpad_acpi: Disabling thinkpad-acpi brightness events by
default...
[ 373.695843] thinkpad_acpi: Standard ACPI backlight interface available, not
loading native one
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2152818
Title:
ThinkPad L13 Yoga Gen 2a: Keyboard backlight not detected in kernel
7.x (thinkpad_acpi does not expose tpacpi::kbd_backlight)
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