[PATCH 3/3] q800: add machine id register

[Laurent Vivier <laurent@vivier.eu>]

MacOS reads this address to identify the hardware.

This is a basic implementation returning the ID of Quadra 800.

Details:

  http://mess.redump.net/mess/driver_info/mac_technical_notes

"There are 3 ID schemes [...]
 The third and most scalable is a machine ID register at 0x5ffffffc.
 The top word must be 0xa55a to be valid. Then bits 15-11 are 0 for
 consumer Macs, 1 for portables, 2 for high-end 68k, and 3 for high-end
 PowerPC. Bit 10 is 1 if additional ID bits appear elsewhere (e.g. in VIA1).
 The rest of the bits are a per-model identifier.

 Model                          Lower 16 bits of ID
...
 Quadra/Centris 610/650/800     0x2BAD"

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 hw/m68k/q800.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/hw/m68k/q800.c b/hw/m68k/q800.c
index 9ee0cb1141..c2b2aa779f 100644
--- a/hw/m68k/q800.c
+++ b/hw/m68k/q800.c
@@ -97,6 +97,23 @@ static void main_cpu_reset(void *opaque)
     cpu->env.pc = ldl_phys(cs->as, 4);
 }
 
+static uint64_t machine_id_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0xa55a2bad; /* Quadra 800 ID */
+}
+
+static void machine_id_write(void *opaque, hwaddr addr, uint64_t val,
+                             unsigned size)
+{
+}
+
+static const MemoryRegionOps machine_id_ops = {
+    .read = machine_id_read,
+    .write = machine_id_write,
+    .valid.min_access_size = 4,
+    .valid.max_access_size = 4,
+};
+
 static void q800_init(MachineState *machine)
 {
     M68kCPU *cpu = NULL;
@@ -110,6 +127,7 @@ static void q800_init(MachineState *machine)
     MemoryRegion *rom;
     MemoryRegion *ram;
     MemoryRegion *io;
+    MemoryRegion *machine_id;
     const int io_slice_nb = (IO_SIZE / IO_SLICE) - 1;
     int i;
     ram_addr_t ram_size = machine->ram_size;
@@ -159,6 +177,10 @@ static void q800_init(MachineState *machine)
         g_free(name);
     }
 
+    machine_id = g_malloc(sizeof(*machine_id));
+    memory_region_init_io(machine_id, NULL, &machine_id_ops, NULL, "Machine ID", 4);
+    memory_region_add_subregion(get_system_memory(), 0x5ffffffc, machine_id);
+
     /* djMEMC memory and interrupt controller */
 
     djmemc_dev = qdev_create(NULL, TYPE_DJMEMC);
-- 
2.23.0