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, 5 insertions, 11 deletions

diff --git a/src/dev/io_device.hh b/src/dev/io_device.hh
index 400263957..9bb2c3d87 100644
--- a/src/dev/io_device.hh
+++ b/src/dev/io_device.hh
@@ -69,7 +69,7 @@ class PioPort : public SimpleTimingPort
 };
 
 
-class DmaPort : public Port
+class DmaPort : public MasterPort
 {
   protected:
     struct DmaReqState : public Packet::SenderState, public FastAlloc
@@ -148,16 +148,9 @@ class DmaPort : public Port
         panic("dma port shouldn't be used for pio access.");
     }
 
-    virtual void recvRangeChange()
-    {
-        // DMA port is a master with a single slave so there is no choice and
-        // thus no need to worry about any address changes
-    }
-
     virtual void recvRetry() ;
 
-    virtual bool isSnooping()
-    { return recvSnoops; }
+    virtual bool isSnooping() const { return recvSnoops; }
 
     void queueDma(PacketPtr pkt, bool front = false);
     void sendDma();
@@ -231,7 +224,7 @@ class PioDevice : public MemObject
 
     virtual unsigned int drain(Event *de);
 
-    virtual Port *getPort(const std::string &if_name, int idx = -1);
+    virtual SlavePort &getSlavePort(const std::string &if_name, int idx = -1);
 
     friend class PioPort;
 
@@ -304,7 +297,8 @@ class DmaDevice : public PioDevice
 
     unsigned cacheBlockSize() const { return dmaPort.cacheBlockSize(); }
 
-    virtual Port *getPort(const std::string &if_name, int idx = -1);
+    virtual MasterPort &getMasterPort(const std::string &if_name,
+                                      int idx = -1);
 
     friend class DmaPort;
 };