src/mem/external_slave.hh

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/**
 * @file
 *
 * ExternalSlave is a memory object representing a binding from
 * a gem5 requestor to a response port in a system external to gem5.
 *
 * During initialisation, a `handler' for the port type specified in the
 * port's port_type parameter is found from the registered port handlers
 * provided with registerHandler.  Once a handler is found, it is passed the
 * port_data parameter of the port which can be used to identify the external
 * port which is to be bound to.  A port handler will usually construct a
 * bridge object in the external system to accomodate the port-to-port
 * mapping but this bridge is not exposed to gem5 other than be the
 * presentation of the SlavePort which can be bound.
 *
 * The external port must provide a gem5 SlavePort interface (with the
 * exception of getAddrRanges which is provided by the ExternalSlave
 * object).
 */

#ifndef __MEM_EXTERNAL_SLAVE_HH__
#define __MEM_EXTERNAL_SLAVE_HH__

#include "mem/port.hh"
#include "params/ExternalSlave.hh"
#include "sim/sim_object.hh"

namespace gem5
{

class ExternalSlave : public SimObject
{
  public:
    /** Derive from this class to create an external port interface */
    class ExternalPort : public ResponsePort
    {
      protected:
        ExternalSlave &owner;

      public:
        ExternalPort(const std::string &name_,
            ExternalSlave &owner_) :
            ResponsePort(name_, &owner_), owner(owner_)
        { }

        ~ExternalPort() { }

        /** Any or all of recv... can be overloaded to provide the port's
         *  functionality */

        AddrRangeList getAddrRanges() const;
    };

    /* Handlers are specific to *types* of port not specific port
     * instantiations.  A handler will typically build a bridge to the
     * external port from gem5 and provide gem5 with a ResponsePort that can be
     * bound to for each call to Handler::getExternalPort.*/
    class Handler
    {
      public:
        /** Create or find an external port which can be bound.  Returns
         *  NULL on failure */
        virtual ExternalPort *getExternalPort(
            const std::string &name, ExternalSlave &owner,
            const std::string &port_data) = 0;
    };

  protected:
    /** The peer port for the gem5 port "port" */
    ExternalPort *externalPort;

    /** Name of the bound port.  This will be name() + ".port" */
    std::string portName;

    /** Key to select a port handler */
    std::string portType;

    /** Handler-specific port configuration */
    std::string portData;

    /** The Range of addresses supported by the devices on the external
     *  side of this port */
    AddrRangeList addrRanges;

    /** Registered handlers.  Handlers are chosen using the port_type
     *  parameter on ExternalSlaves.  port_types form a global namespace
     *  across the simulation and so handlers are registered into a global
     *  structure */
    static std::map<std::string, Handler *> portHandlers;

  public:
    ExternalSlave(const ExternalSlaveParams &params);

    /** Port interface.  Responds only to port "port" */
    Port &getPort(const std::string &if_name,
                  PortID idx=InvalidPortID) override;

    /** Register a handler which can provide ports with port_type ==
     *  handler_name */
    static void registerHandler(const std::string &handler_name,
        Handler *handler);

    void init() override;
};

} // namespace gem5

#endif //__MEM_EXTERNAL_SLAVE_HH__