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+/*
+ * Copyright (c) 2014, 2017 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#ifndef __DEV_SERIAL_HH__
+#define __DEV_SERIAL_HH__
+
+#include "base/callback.hh"
+#include "sim/sim_object.hh"
+
+struct SerialDeviceParams;
+struct SerialNullDeviceParams;
+
+/**
+ * Base class for serial devices such as terminals.
+ *
+ * This class provides a unified interface that all serial (RS232 or
+ * similar) devices must implement. A device can be wired to exactly
+ * one host serial interface (serial port model).
+ *
+ * SerialDevices are passive devices that are <i>driven</i> by the
+ * serial interface using the writeData(c) (the interface sends a
+ * character) and readData() (the interface reads a character)
+ * methods. Serial devices need to override these methods to
+ * communicate with the host interface layer.
+ *
+ * To implement basic flow control, serial devices must implement the
+ * dataAvailable() method. This method returns true if a valid
+ * character can be read using the readData() method. When data
+ * becomes available, the serial device must call the
+ * notifyInterface() method to send a callback to the interface layer.
+ *
+ * To send a character (host to device), the interface layer calls
+ * writeData(char) to send a character to the serial device.
+ *
+ * To read a character (device to host), the interface layer calls
+ * dataAvailable() to determine if there is a character pending. If
+ * there is data available, it immediately calls readData() to get the
+ * character. The receive loop in the serial device typically looks
+ * like this:
+ *
+ * \code{.cc}
+ * while (device.dataAvailable()) {
+ *    printf("%c", (int)device.readData());
+ * }
+ * \endcode
+ *
+ * To avoid polling, the interface layer may register a data available
+ * callback using the regInterfaceCallback() method. The device uses
+ * this callback to notify the interface layer whenever there is new
+ * data pending. Note that devices will normally only notify the
+ * interface layer when there is a state transition in the
+ * device. E.g., the dataAvailable() transitions from false to
+ * true. This means that there can be multiple pending characters when
+ * the interface layer receives the callback.
+ */
+class SerialDevice : public SimObject
+{
+  public:
+    SerialDevice(const SerialDeviceParams *p);
+    ~SerialDevice();
+
+  public: // Serial device API (UART->Device)
+    /**
+     * Register a data available callback into the host interface layer.
+     *
+     * Serial devices need to call the underlying host interface layer
+     * to inform it of state change such as pending data that can be
+     * read from the device by the interface layer using the readData()
+     * method. The interface layer may use this method to register a
+     * callback that informs it of pending data.
+     *
+     * @param c Callback instance from interface layer.
+     */
+    void regInterfaceCallback(Callback *c);
+
+    /**
+     * Check if there is pending data from the serial device.
+     *
+     * @return true if there is data pending that can be read using
+     * the readData() method.
+     */
+    virtual bool dataAvailable() const = 0;
+
+    /**
+     * Transmit a character from the host interface to the device.
+     *
+     * @param c Received data.
+     */
+    virtual void writeData(uint8_t c) = 0;
+
+    /**
+     * Read a character from the device.
+     *
+     * @return Character from the device's output buffer, undefined if
+     * no data is pending.
+     */
+    virtual uint8_t readData() = 0;
+
+  protected:
+    /** Notify the host interface of pending data. */
+    void notifyInterface();
+
+  private:
+    /** Currently regisxtered host interface layer callback */
+    Callback *interfaceCallback;
+};
+
+/**
+ * Dummy serial device that discards all data sent to it.
+ */
+class SerialNullDevice : public SerialDevice
+{
+  public:
+    SerialNullDevice(const SerialNullDeviceParams *p);
+
+  public:
+    bool dataAvailable() const override { return false; }
+    void writeData(uint8_t c) override {};
+    uint8_t readData() override;
+};
+
+#endif // __DEV_SERIAL_HH__