Add message_handler application

This is an example application for communication with Ethos-U kernel driver

Change-Id: I1d602682cbfdf26a2b082a56ee6c38e93a49ab8d
diff --git a/applications/message_handler/message_handler.hpp b/applications/message_handler/message_handler.hpp
new file mode 100644
index 0000000..5a195f0
--- /dev/null
+++ b/applications/message_handler/message_handler.hpp
@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2020-2021 Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * 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
+ *
+ * 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.
+ */
+
+#ifndef MESSAGE_HANDLER_H
+#define MESSAGE_HANDLER_H
+
+#include "FreeRTOS.h"
+#include "queue.h"
+#include "semphr.h"
+
+#include "message_queue.hpp"
+#include <inference_process.hpp>
+#include <mailbox.hpp>
+
+#include <cstddef>
+#include <cstdio>
+#include <vector>
+
+namespace MessageHandler {
+
+class IncomingMessageHandler {
+public:
+    IncomingMessageHandler(EthosU::ethosu_core_queue &messageQueue,
+                           Mailbox::Mailbox &mailbox,
+                           QueueHandle_t inferenceQueue,
+                           QueueHandle_t outputQueue);
+    void run();
+
+private:
+    bool handleMessage();
+    void queueErrorAndResetQueue(EthosU::ethosu_core_msg_err_type type, const char *message);
+    static void handleIrq(void *userArg);
+
+    MessageQueue::QueueImpl messageQueue;
+    Mailbox::Mailbox &mailbox;
+    QueueHandle_t inferenceQueue;
+    QueueHandle_t outputQueue;
+    SemaphoreHandle_t semaphore;
+};
+
+class InferenceHandler {
+public:
+    InferenceHandler(uint8_t *tensorArena, size_t arenaSize, QueueHandle_t inferenceQueue, QueueHandle_t outputQueue);
+
+    void run();
+
+private:
+    void runInference(EthosU::ethosu_core_inference_req &req, EthosU::ethosu_core_inference_rsp &rsp);
+
+    QueueHandle_t inferenceQueue;
+    QueueHandle_t outputQueue;
+    InferenceProcess::InferenceProcess inference;
+};
+
+struct OutputMessage {
+    OutputMessage(EthosU::ethosu_core_msg_type _type = EthosU::ETHOSU_CORE_MSG_MAX) : type(_type) {}
+
+    EthosU::ethosu_core_msg_type type;
+    union {
+        EthosU::ethosu_core_inference_rsp inference;
+        EthosU::ethosu_core_msg_err error;
+        uint64_t userArg;
+    } data;
+};
+
+class OutgoingMessageHandler {
+public:
+    OutgoingMessageHandler(EthosU::ethosu_core_queue &messageQueue,
+                           Mailbox::Mailbox &mailbox,
+                           QueueHandle_t outputQueue);
+    void run();
+
+private:
+    void sendPong();
+    void sendErrorRsp(EthosU::ethosu_core_msg_err &error);
+    void sendVersionRsp();
+    void sendCapabilitiesRsp(uint64_t userArg);
+    void sendInferenceRsp(EthosU::ethosu_core_inference_rsp &inference);
+    void readCapabilties(EthosU::ethosu_core_msg_capabilities_rsp &rsp);
+
+    MessageQueue::QueueImpl messageQueue;
+    Mailbox::Mailbox &mailbox;
+    QueueHandle_t outputQueue;
+    EthosU::ethosu_core_msg_capabilities_rsp capabilities;
+};
+
+} // namespace MessageHandler
+
+#endif