Re: [PATCH v3 1/7] platform/x86: thinkpad_acpi: Report auto keyboard backlight mode as off

[Rong Zhang <i@rong.moe>]

Hi Qiling,

On Sun, 2026-11-15 at 01:48 +0800, Qiling Zhu wrote:
> The EC keyboard backlight level 3, which selects the auto mode, is
> passed to the LED classdev verbatim by kbdlight_sysfs_get().  The LED
> then reports a brightness of 3 with max_brightness 2, both through the
> brightness sysfs attribute and through brightness_hw_changed
> notifications.
> 
> This is not only cosmetic: UPower 1.91.x treats the out-of-range value as
> invalid and stops watching brightness_hw_changed altogether, so the desktop
> stops following the Fn+Space hotkey once auto mode has been entered.
> 
> The auto mode is not a brightness level.  Map it to 0, the value it is
> reported as most of the time anyway, in line with what ideapad-laptop
> already does for its auto mode.
> 
> Fixes: bb28f3d51ff5 ("thinkpad_acpi: Add support for keyboard backlight")
> Reported-by: Andrea Rabbaglietti <rabbagliettiandrea@gmail.com>
> Closes: https://lore.kernel.org/r/CAENjc+w0Rqy=kDSew7XtNJCSvyPiXPJ5faWdmCr5RGYFhpunCA@mail.gmail.com
> Cc: stable@vger.kernel.org
> Signed-off-by: Qiling Zhu <kmatzkaczor244@gmail.com>

Reviewed-by: Rong Zhang <i@rong.moe>

Thanks,
Rong

> ---
>  drivers/platform/x86/lenovo/thinkpad_acpi.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> index 4f81855ad..2c3f8cf32 100644
> --- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
> +++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> @@ -5102,6 +5102,9 @@ static struct ibm_struct video_driver_data = {
>   * Keyboard backlight subdriver
>   */
>  
> +/* EC level that selects the auto mode for the keyboard backlight */
> +#define TPACPI_KBD_LIGHT_AUTO_LEVEL 3
> +
>  static enum led_brightness kbdlight_brightness;
>  static DEFINE_MUTEX(kbdlight_mutex);
>  
> @@ -5191,7 +5194,8 @@ static enum led_brightness kbdlight_sysfs_get(struct led_classdev *led_cdev)
>  	int level;
>  
>  	level = kbdlight_get_level();
> -	if (level < 0)
> +	/* Auto mode is not a brightness level; report it as off. */
> +	if (level < 0 || level == TPACPI_KBD_LIGHT_AUTO_LEVEL)
>  		return 0;
>  
>  	return level;