Add Machine ID register for the Gossamer architecture.

devices/machineid.h

@@ -0,0 +1,37 @@
+#ifndef MACHINE_ID_H
+#define MACHINE_ID_H
+
+#include <cinttypes>
+#include "mmiodevice.h"
+
+/**
+    @file Contains definitions for PowerMacintosh machine ID registers.
+
+    The machine ID register is a memory-based register containing hardcoded
+    values the system software can read to identify machine/board it's running on.
+
+    Register location and value meaning are board-dependent.
+ */
+
+/**
+    The machine ID for the Gossamer board is accesible at 0xFF000004 (phys).
+    It contains a 16-bit value revealing machine's capabilities like bus speed,
+    ROM speed, I/O configuration etc.
+    Because the meaning of these bits is poorly documented, the code below
+    simply return raw values obtained from real hardware.
+ */
+class GossamerID : public MMIODevice {
+public:
+    GossamerID(const uint16_t id) { this->id = id, this->name = "Machine-id"; };
+    ~GossamerID() = default;
+
+    uint32_t read(uint32_t offset, int size) {
+         return ((!offset && size == 2) ? this->id : 0); };
+
+    void write(uint32_t offset, uint32_t value, int size) {}; /* not writable */
+
+private:
+    uint16_t id;
+};
+
+#endif /* MACHINE_ID_H */

main.cpp

@@ -25,6 +25,7 @@
 #include "devices/mpc106.h"
 #include "openpic.h"
 #include "debugger.h"
+#include "devices/machineid.h"
 #include "devices/macio.h"
 #include "devices/mpc106.h"
 
@@ -84,6 +85,7 @@ uint32_t return_value;
 
 MemCtrlBase *mem_ctrl_instance = 0;
 HeathrowIC  *heathrow = 0;
+GossamerID  *machine_id;
 
 //A pointer to a pointer, used for quick movement to one of the following
 //memory areas. These are listed right below.
@@ -557,6 +559,10 @@ int main(int argc, char **argv)
                 romFile.close();
                 return 1;
             }
+            machine_id = new GossamerID(0x3d8c);
+            assert(machine_id != 0);
+            mpc106->add_mmio_region(0xFF000004, 4096, machine_id);
+
             heathrow = new HeathrowIC();
             assert(heathrow != 0);
             mpc106->pci_register_device(16, heathrow);
@@ -791,6 +797,7 @@ int main(int argc, char **argv)
     }
 
     delete(heathrow);
+    delete(machine_id);
     delete(mem_ctrl_instance);
 
     //Free memory after the emulation is completed.