platform/x86: asus-wmi: fix screenpad brightness range

Fix screenpad brightness range being too limited without reason:
testing this patch on a Zenbook Duo showed the hardware minimum not being
too low, therefore allow the user to configure the entire range, and
expose to userspace the hardware brightness range and value.

Fixes: 2c97d3e55b70 ("platform/x86: asus-wmi: add support for ASUS screenpad")
Signed-off-by: Denis Benato <denis.benato@linux.dev>
Signed-off-by: Luke Jones <luke@ljones.dev>
Link: https://patch.msgid.link/20260302174431.349816-3-denis.benato@linux.dev
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index f4a5da5b1bb8716091584ab0df5d57099200d2d1..80144c412b902f33811da48fe0433092678cb928 100644 (file)
--- 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
 
@@ -4411,13 +4410,13 @@ 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)
@@ -4457,22 +4456,19 @@ 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);
@@ -4483,7 +4479,7 @@ 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);