Fix incorrect brightness scaling by removing the inconsistent use of an
arbitrary minimum.

Signed-off-by: Denis Benato <denis.benato@linux.dev>
Signed-off-by: Luke Jones <luke@ljones.dev>
---
 drivers/platform/x86/asus-wmi.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 4130dae37e15..5443aaf99e38 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -125,7 +125,6 @@ module_param(fnlock_default, bool, 0444);
 #define NVIDIA_TEMP_MIN		75
 #define NVIDIA_TEMP_MAX		87
 
-#define ASUS_SCREENPAD_BRIGHT_MIN 20
 #define ASUS_SCREENPAD_BRIGHT_MAX 255
 #define ASUS_SCREENPAD_BRIGHT_DEFAULT 60
 
@@ -4243,13 +4242,13 @@ static int read_screenpad_brightness(struct backlight_device *bd)
 		return err;
 	/* The device brightness can only be read if powered, so return stored */
 	if (err == BACKLIGHT_POWER_OFF)
-		return asus->driver->screenpad_brightness - ASUS_SCREENPAD_BRIGHT_MIN;
+		return bd->props.brightness;
 
 	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &retval);
 	if (err < 0)
 		return err;
 
-	return (retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK) - ASUS_SCREENPAD_BRIGHT_MIN;
+	return (retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK);
 }
 
 static int update_screenpad_bl_status(struct backlight_device *bd)
@@ -4289,22 +4288,19 @@ static int asus_screenpad_init(struct asus_wmi *asus)
 	int err, power;
 	int brightness = 0;
 
-	power = read_screenpad_backlight_power(asus);
+	power = asus_wmi_get_devstate_simple(asus, ASUS_WMI_DEVID_SCREENPAD_POWER);
 	if (power < 0)
 		return power;
 
-	if (power != BACKLIGHT_POWER_OFF) {
+	if (power) {
 		err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &brightness);
 		if (err < 0)
 			return err;
 	}
-	/* default to an acceptable min brightness on boot if too low */
-	if (brightness < ASUS_SCREENPAD_BRIGHT_MIN)
-		brightness = ASUS_SCREENPAD_BRIGHT_DEFAULT;
 
 	memset(&props, 0, sizeof(struct backlight_properties));
 	props.type = BACKLIGHT_RAW; /* ensure this bd is last to be picked */
-	props.max_brightness = ASUS_SCREENPAD_BRIGHT_MAX - ASUS_SCREENPAD_BRIGHT_MIN;
+	props.max_brightness = ASUS_SCREENPAD_BRIGHT_MAX;
 	bd = backlight_device_register("asus_screenpad",
 				       &asus->platform_device->dev, asus,
 				       &asus_screenpad_bl_ops, &props);
@@ -4315,7 +4311,7 @@ static int asus_screenpad_init(struct asus_wmi *asus)
 
 	asus->screenpad_backlight_device = bd;
 	asus->driver->screenpad_brightness = brightness;
-	bd->props.brightness = brightness - ASUS_SCREENPAD_BRIGHT_MIN;
+	bd->props.brightness = brightness;
 	bd->props.power = power;
 	backlight_update_status(bd);
 
-- 
2.53.0

On Thu, 12 Feb 2026, Denis Benato wrote:

> Fix incorrect brightness scaling by removing the inconsistent use of an
> arbitrary minimum.
> 
> Signed-off-by: Denis Benato <denis.benato@linux.dev>
> Signed-off-by: Luke Jones <luke@ljones.dev>

Should this have a Fixes tag?

> ---
>  drivers/platform/x86/asus-wmi.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
> index 4130dae37e15..5443aaf99e38 100644
> --- a/drivers/platform/x86/asus-wmi.c
> +++ b/drivers/platform/x86/asus-wmi.c
> @@ -125,7 +125,6 @@ module_param(fnlock_default, bool, 0444);
>  #define NVIDIA_TEMP_MIN		75
>  #define NVIDIA_TEMP_MAX		87
>  
> -#define ASUS_SCREENPAD_BRIGHT_MIN 20
>  #define ASUS_SCREENPAD_BRIGHT_MAX 255
>  #define ASUS_SCREENPAD_BRIGHT_DEFAULT 60
>  
> @@ -4243,13 +4242,13 @@ static int read_screenpad_brightness(struct backlight_device *bd)
>  		return err;
>  	/* The device brightness can only be read if powered, so return stored */
>  	if (err == BACKLIGHT_POWER_OFF)
> -		return asus->driver->screenpad_brightness - ASUS_SCREENPAD_BRIGHT_MIN;
> +		return bd->props.brightness;
>  
>  	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &retval);
>  	if (err < 0)
>  		return err;
>  
> -	return (retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK) - ASUS_SCREENPAD_BRIGHT_MIN;
> +	return (retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK);
>  }
>  
>  static int update_screenpad_bl_status(struct backlight_device *bd)
> @@ -4289,22 +4288,19 @@ static int asus_screenpad_init(struct asus_wmi *asus)
>  	int err, power;
>  	int brightness = 0;
>  
> -	power = read_screenpad_backlight_power(asus);
> +	power = asus_wmi_get_devstate_simple(asus, ASUS_WMI_DEVID_SCREENPAD_POWER);
>  	if (power < 0)
>  		return power;
>  
> -	if (power != BACKLIGHT_POWER_OFF) {
> +	if (power) {
>  		err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &brightness);
>  		if (err < 0)
>  			return err;
>  	}
> -	/* default to an acceptable min brightness on boot if too low */
> -	if (brightness < ASUS_SCREENPAD_BRIGHT_MIN)
> -		brightness = ASUS_SCREENPAD_BRIGHT_DEFAULT;

This doesn't seem to be related to the scaling but looks a lowerbound? 
Probably removing it would warrant own patch + justification, IMO.

>  	memset(&props, 0, sizeof(struct backlight_properties));
>  	props.type = BACKLIGHT_RAW; /* ensure this bd is last to be picked */
> -	props.max_brightness = ASUS_SCREENPAD_BRIGHT_MAX - ASUS_SCREENPAD_BRIGHT_MIN;
> +	props.max_brightness = ASUS_SCREENPAD_BRIGHT_MAX;
>  	bd = backlight_device_register("asus_screenpad",
>  				       &asus->platform_device->dev, asus,
>  				       &asus_screenpad_bl_ops, &props);
> @@ -4315,7 +4311,7 @@ static int asus_screenpad_init(struct asus_wmi *asus)
>  
>  	asus->screenpad_backlight_device = bd;
>  	asus->driver->screenpad_brightness = brightness;
> -	bd->props.brightness = brightness - ASUS_SCREENPAD_BRIGHT_MIN;
> +	bd->props.brightness = brightness;
>  	bd->props.power = power;
>  	backlight_update_status(bd);
>  
> 

--
 i.