Bluetooth: Mesh: avoid double conversion precision losing

Commit solves situation when the level client sends
Set command with exact values but Status has different levels.
It happens when Level model extends the temperature model.
Double conversion happens. Conversions from level
to temperature and back have division result rounding
that causes precision losing.

Signed-off-by: Aleksandr Khromykh <aleksandr.khromykh@nordicsemi.no>

subsys/bluetooth/mesh/light_temp_srv.c

@@ -179,9 +179,10 @@ static void lvl_set(struct bt_mesh_lvl_srv *lvl_srv,
 	struct bt_mesh_light_temp_srv *srv =
 		CONTAINER_OF(lvl_srv, struct bt_mesh_light_temp_srv, lvl);
 	struct bt_mesh_light_temp_status status = { 0 };
+	uint16_t temp = lvl_to_temp(srv, lvl_set->lvl);
 	struct bt_mesh_light_temp_set set = {
 		.params = {
-			.temp = lvl_to_temp(srv, lvl_set->lvl),
+			.temp = temp,
 			.delta_uv = srv->transient.last.delta_uv,
 		},
 		.transition = lvl_set->transition,
@@ -194,8 +195,15 @@ static void lvl_set(struct bt_mesh_lvl_srv *lvl_srv,
 	}
 
 	if (rsp) {
-		rsp->current = temp_to_lvl(srv, status.current.temp);
-		rsp->target = temp_to_lvl(srv, status.target.temp);
+		/* This helps to avoid weird situation when client sets exact level value
+		 * but after conversion to temperature and back from temperature to level,
+		 * the level value is changed in Status.
+		 * It happens due to the division results rounding in both conversions.
+		 */
+		rsp->current = temp == status.current.temp ? lvl_set->lvl
+							   : temp_to_lvl(srv, status.current.temp);
+		rsp->target = temp == status.target.temp ? lvl_set->lvl
+							 : temp_to_lvl(srv, status.target.temp);
 		rsp->remaining_time = status.remaining_time;
 	}
 }