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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__
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