mem, sim, systemc: Reorganize Port and co.s bind, unbind slightly.

The base Port class can keep track of its peer, and also whether it's
connected. This is partially delegated away from the port subclasses
which still keep track of a cast version of their peer pointer for
their own conveneince, so that it can be used by generic code. Even
with the Port mechanism's new flexibility, each port still has
exactly one peer and is either connected or not based on whether there
is a peer currently.

Change-Id: Id3228617dd1604d196814254a1aadeac5ade7cde
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20232
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

2 files changed, 23 insertions, 3 deletions

diff --git a/src/sim/port.cc b/src/sim/port.cc
index b3139a630..fa7df18cf 100644
--- a/src/sim/port.cc
+++ b/src/sim/port.cc
@@ -50,6 +50,6 @@
 #include "sim/port.hh"
 
 Port::Port(const std::string& _name, PortID _id) :
-    portName(_name), id(_id), _connected(false)
+    portName(_name), id(_id), _peer(nullptr), _connected(false)
 {}
 Port::~Port() {}
diff --git a/src/sim/port.hh b/src/sim/port.hh
index e1811643f..ee4b548a5 100644
--- a/src/sim/port.hh
+++ b/src/sim/port.hh
@@ -72,6 +72,13 @@ class Port
      * to InvalidPortID in case this port is not part of a vector.
      */
     const PortID id;
+
+    /**
+     * A pointer to this port's peer.
+     */
+    Port *_peer;
+
+
     /**
      * Whether this port is currently connected to a peer port.
      */
@@ -92,6 +99,9 @@ class Port
 
   public:
 
+    /** Return a reference to this port's peer. */
+    Port &getPeer() { return *_peer; }
+
     /** Return port name (for DPRINTF). */
     const std::string name() const { return portName; }
 
@@ -99,10 +109,20 @@ class Port
     PortID getId() const { return id; }
 
     /** Attach to a peer port. */
-    virtual void bind(Port &peer) = 0;
+    virtual void
+    bind(Port &peer)
+    {
+        _peer = &peer;
+        _connected = true;
+    }
 
     /** Dettach from a peer port. */
-    virtual void unbind() = 0;
+    virtual void
+    unbind()
+    {
+        _peer = nullptr;
+        _connected = false;
+    }
 
     /** Is this port currently connected to a peer? */
     bool isConnected() const { return _connected; }