Add Oplink attenuation extension and channel power drivers.

Change-Id: I2558595b03cbb6cc58237dc48b8a03e83357fe1f
diff --git a/drivers/default/src/main/java/org/onosproject/driver/extensions/codec/OplinkAttenuationCodec.java b/drivers/default/src/main/java/org/onosproject/driver/extensions/codec/OplinkAttenuationCodec.java
new file mode 100644
index 0000000..ed2da00
--- /dev/null
+++ b/drivers/default/src/main/java/org/onosproject/driver/extensions/codec/OplinkAttenuationCodec.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.driver.extensions.codec;
+
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.onosproject.codec.CodecContext;
+import org.onosproject.codec.JsonCodec;
+import org.onosproject.driver.extensions.OplinkAttenuation;
+
+import static org.onlab.util.Tools.nullIsIllegal;
+
+/**
+ * JSON Codec for OplinkAttenuation class.
+ */
+public class OplinkAttenuationCodec extends JsonCodec<OplinkAttenuation> {
+    private static final String ATTENUATION = "attenuation";
+    private static final String MISSING_ATT = "Missing value for \"attenuation\"";
+
+    @Override
+    public OplinkAttenuation decode(ObjectNode json, CodecContext context) {
+        if (json == null || !json.isObject()) {
+            return null;
+        }
+        String att = nullIsIllegal(json.get(ATTENUATION), MISSING_ATT).asText();
+        return new OplinkAttenuation(Integer.valueOf(att));
+    }
+}