platform/x86: asus-wmi: adjust screenpad power/brightness handling

[ Upstream commit 130d29c ]

Fix illogical screen off control by hardcoding 0 and 1 depending on the
requested brightness and also do not rely on the last screenpad power
state to issue screen brightness commands.

Fixes: 2c97d3e ("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/20260302174431.349816-2-denis.benato@linux.dev
Link: https://patch.msgid.link/20260326231154.856729-2-ethantidmore06@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: NeroReflex

drivers/platform/x86/asus-wmi.c

@@ -4154,32 +4154,24 @@ static int read_screenpad_brightness(struct backlight_device *bd)
 
 static int update_screenpad_bl_status(struct backlight_device *bd)
 {
-	struct asus_wmi *asus = bl_get_data(bd);
-	int power, err = 0;
-	u32 ctrl_param;
+	u32 ctrl_param = bd->props.brightness;
+	int err = 0;
 
-	power = read_screenpad_backlight_power(asus);
-	if (power < 0)
-		return power;
+	if (bd->props.power) {
+		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 1, NULL);
+		if (err < 0)
+			return err;
 
-	if (bd->props.power != power) {
-		if (power != BACKLIGHT_POWER_ON) {
-			/* Only brightness > 0 can power it back on */
-			ctrl_param = asus->driver->screenpad_brightness - ASUS_SCREENPAD_BRIGHT_MIN;
-			err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT,
-						    ctrl_param, NULL);
-		} else {
-			err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 0, NULL);
-		}
-	} else if (power == BACKLIGHT_POWER_ON) {
-		/* Only set brightness if powered on or we get invalid/unsync state */
-		ctrl_param = bd->props.brightness + ASUS_SCREENPAD_BRIGHT_MIN;
 		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT, ctrl_param, NULL);
+		if (err < 0)
+			return err;
 	}
 
-	/* Ensure brightness is stored to turn back on with */
-	if (err == 0)
-		asus->driver->screenpad_brightness = bd->props.brightness + ASUS_SCREENPAD_BRIGHT_MIN;
+	if (!bd->props.power) {
+		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 0, NULL);
+		if (err < 0)
+			return err;
+	}
 
 	return err;
 }