MEM: Introduce the master/slave port sub-classes in C++

This patch introduces the notion of a master and slave port in the C++
code, thus bringing the previous classification from the Python
classes into the corresponding simulation objects and memory objects.

The patch enables us to classify behaviours into the two bins and add
assumptions and enfore compliance, also simplifying the two
interfaces. As a starting point, isSnooping is confined to a master
port, and getAddrRanges to slave ports. More of these specilisations
are to come in later patches.

The getPort function is not getMasterPort and getSlavePort, and
returns a port reference rather than a pointer as NULL would never be
a valid return value. The default implementation of these two
functions is placed in MemObject, and calls fatal.

The one drawback with this specific patch is that it requires some
code duplication, e.g. QueuedPort becomes QueuedMasterPort and
QueuedSlavePort, and BusPort becomes BusMasterPort and BusSlavePort
(avoiding multiple inheritance). With the later introduction of the
port interfaces, moving the functionality outside the port itself, a
lot of the duplicated code will disappear again.

1 files changed, 45 insertions, 5 deletions

diff --git a/src/mem/qport.hh b/src/mem/qport.hh
index 39612d22f..6ee71a572 100644
--- a/src/mem/qport.hh
+++ b/src/mem/qport.hh
@@ -56,7 +56,7 @@
  * queue is a parameter to allow tailoring of the queue implementation
  * (used in the cache).
  */
-class QueuedPort : public Port
+class QueuedSlavePort : public SlavePort
 {
 
   protected:
@@ -68,7 +68,46 @@ class QueuedPort : public Port
       * packet again. */
     virtual void recvRetry() { queue.retry(); }
 
-    virtual void recvRangeChange() { }
+  public:
+
+    /**
+     * Create a QueuedPort with a given name, owner, and a supplied
+     * implementation of a packet queue. The external definition of
+     * the queue enables e.g. the cache to implement a specific queue
+     * behaviuor in a subclass, and provide the latter to the
+     * QueuePort constructor.
+     */
+    QueuedSlavePort(const std::string& name, MemObject* owner,
+                    PacketQueue &queue) :
+        SlavePort(name, owner), queue(queue)
+    { }
+
+    virtual ~QueuedSlavePort() { }
+
+    /** Check the list of buffered packets against the supplied
+     * functional request. */
+    bool checkFunctional(PacketPtr pkt) { return queue.checkFunctional(pkt); }
+
+    /**
+     * Hook for draining the queued port.
+     *
+     * @param de an event which is used to signal back to the caller
+     * @returns a number indicating how many times process will be called
+     */
+    unsigned int drain(Event *de) { return queue.drain(de); }
+};
+
+class QueuedMasterPort : public MasterPort
+{
+
+  protected:
+
+    /** Packet queue used to store outgoing requests and responses. */
+    PacketQueue &queue;
+
+     /** This function is notification that the device should attempt to send a
+      * packet again. */
+    virtual void recvRetry() { queue.retry(); }
 
   public:
 
@@ -79,11 +118,12 @@ class QueuedPort : public Port
      * behaviuor in a subclass, and provide the latter to the
      * QueuePort constructor.
      */
-    QueuedPort(const std::string& name, MemObject* owner, PacketQueue &queue) :
-        Port(name, owner), queue(queue)
+    QueuedMasterPort(const std::string& name, MemObject* owner,
+                    PacketQueue &queue) :
+        MasterPort(name, owner), queue(queue)
     { }
 
-    virtual ~QueuedPort() { }
+    virtual ~QueuedMasterPort() { }
 
     /** Check the list of buffered packets against the supplied
      * functional request. */