asus-wmi: don't update power and brightness when using scalar

But we can still do it on other boards, as this might happen
if the backlight driver change when update_bl is called.
Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/asus-wmi.c

@@ -1152,7 +1152,13 @@ static int update_bl_status(struct backlight_device *bd)
 					    ctrl_param, NULL);
 		if (asus->driver->quirks->store_backlight_power)
 			asus->driver->panel_power = bd->props.power;
-	} else {
+
+		/* When using scalar brightness, updating the brightness
+		 * will mess with the backlight power */
+		if (asus->driver->quirks->scalar_panel_brightness)
+			return err;
+	}
+
 	if (asus->driver->quirks->scalar_panel_brightness)
 		ctrl_param = get_scalar_command(bd);
 	else
@@ -1160,7 +1166,7 @@ static int update_bl_status(struct backlight_device *bd)
 
 	err = asus_wmi_set_devstate(ASUS_WMI_DEVID_BRIGHTNESS,
 				    ctrl_param, NULL);
-	}
+
 	return err;
 }