Extend knx brightness with rgb brightness if brightness addres… (#33152)

* Extend knx brightness with rgb brightness if brightness addresses are not supported

* Fix explicit return value

* Check for None

* Remove not needed check

* Disable false positive pylint warning

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

homeassistant/components/knx/light.py

@@ -180,9 +180,13 @@ class KNXLight(Light):
     @property
     def brightness(self):
         """Return the brightness of this light between 0..255."""
-        if not self.device.supports_brightness:
-            return None
-        return self.device.current_brightness
+        if self.device.supports_brightness:
+            return self.device.current_brightness
+        hsv_color = self._hsv_color
+        if self.device.supports_color and hsv_color:
+            # pylint: disable=unsubscriptable-object
+            return round(hsv_color[-1] / 100 * 255)
+        return None
 
     @property
     def hs_color(self):
@@ -192,6 +196,14 @@ class KNXLight(Light):
             rgb, _ = self.device.current_color
         return color_util.color_RGB_to_hs(*rgb) if rgb else None
 
+    @property
+    def _hsv_color(self):
+        """Return the HSV color value."""
+        rgb = None
+        if self.device.supports_rgbw or self.device.supports_color:
+            rgb, _ = self.device.current_color
+        return color_util.color_RGB_to_hsv(*rgb) if rgb else None
+
     @property
     def white_value(self):
         """Return the white value."""