Public bug reported:
# [REGRESSION] ASUS V16 V3607VM: Keyboard backlight Fn+F4 cycling stuck
at level 1 on kernel 7.0
## Description
I am experiencing a keyboard backlight issue on my ASUS V16 V3607VM
running Linux Mint 22.3 Cinnamon.
**With kernel 7.0.0-38-generic, pressing Fn+F4 repeatedly always sets
the physical keyboard backlight to brightness level 1, instead of
cycling through the available levels (0 → 1 → 2 → 3 → 0).**
Interestingly, the cycle works normally at the graphical login screen,
but stops working after logging into Cinnamon.
**Rebooting with kernel 6.14.0-37-generic completely restores the normal
Fn+F4 cycle**, including inside the same Cinnamon session.
Disabling Cinnamon's keyboard brightness shortcuts did not resolve the
issue under kernel 7.0.
## Additional issue: Incorrect brightness reporting
Under **both kernels (6.14 and 7.0)**, the standard keyboard brightness
interface reports an incorrect value.
For example:
```bash
cat /sys/class/leds/asus::kbd_backlight/brightness
```
Always returns:
```text
0
```
Even when the keyboard is physically illuminated at maximum brightness
(level 3).
UPower and Cinnamon also report brightness level 0, despite the physical
keyboard being illuminated.
However, setting the brightness programmatically works correctly. For
example, calling Cinnamon's `Keyboard.SetPercentage 100` method
physically sets the keyboard brightness to maximum.
Under kernel 6.14, the following attribute correctly reports the
physical brightness level after each Fn+F4 press:
```bash
cat /sys/class/leds/asus::kbd_backlight/brightness_hw_changed
```
It returns 0, 1, 2 or 3 according to the selected physical brightness
level.
This suggests that hardware brightness changes are correctly reported
through `brightness_hw_changed`, while the normal brightness reading is
incorrect.
## System information
- **Laptop:** ASUS V16 V3607VM
- **BIOS:** 3607VM.302 (April 24, 2025)
- **Distribution:** Linux Mint 22.3 Cinnamon (Ubuntu 24.04 base)
- **Display server:** X11
- **Working kernel:** `6.14.0-37-generic`
- **Affected kernel:** `7.0.0-38-generic`
- **Keyboard backlight device:** `asus::kbd_backlight`
- **Maximum brightness:** 3
Both kernels are installed from the official Ubuntu repositories.
## Expected behavior
Fn+F4 should cycle through all four brightness levels, including after
logging into Cinnamon.
The standard brightness interface should also report the actual keyboard
backlight level.
## Actual behavior
- **Kernel 6.14:** Fn+F4 cycles normally, but the standard brightness reading
remains incorrect.
- **Kernel 7.0, before login:** Fn+F4 cycles normally.
- **Kernel 7.0, after login:** Fn+F4 repeatedly returns the keyboard to level
1, while brightness readings remain incorrect.
## Possible cause
This may involve an interaction between the ASUS keyboard backlight
driver (`asus-wmi` / `hid-asus`) and desktop power management.
The incorrect brightness reading exists under both kernels, but only
kernel 7.0 exhibits the cycling failure in my Cinnamon session.
I have not identified the exact cause and cannot yet rule out an
interaction with my existing session configuration.
I would appreciate guidance on whether this is a known kernel regression
and what additional diagnostics would help identify the responsible
component.
** Affects: ubuntu
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2171178
Title:
[REGRESSION] ASUS V16 V3607VM: Keyboard backlight Fn+F4 cycling stuck
at level 1 on kernel 7.0
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