q800: implement additional machine id bits on VIA1 port A

Co-developed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231004083806.757242-5-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

hw/misc/mac_via.c

@@ -114,6 +114,9 @@
 #define VIA1A_CPUID1    0x04    /* CPU id bit 0 on RBV, others */
 #define VIA1A_CPUID2    0x10    /* CPU id bit 0 on RBV, others */
 #define VIA1A_CPUID3    0x40    /* CPU id bit 0 on RBV, others */
+#define VIA1A_CPUID_MASK (VIA1A_CPUID0 | VIA1A_CPUID1 | \
+                          VIA1A_CPUID2 | VIA1A_CPUID3)
+#define VIA1A_CPUID_Q800 (VIA1A_CPUID0 | VIA1A_CPUID2)
 
 /*
  * Info on VIA1B is from Macintosh Family Hardware & MkLinux.
@@ -872,9 +875,18 @@ static uint64_t mos6522_q800_via1_read(void *opaque, hwaddr addr, unsigned size)
 {
     MOS6522Q800VIA1State *s = MOS6522_Q800_VIA1(opaque);
     MOS6522State *ms = MOS6522(s);
+    uint64_t ret;
 
     addr = (addr >> 9) & 0xf;
-    return mos6522_read(ms, addr, size);
+    ret = mos6522_read(ms, addr, size);
+    switch (addr) {
+    case VIA_REG_A:
+    case VIA_REG_ANH:
+        /* Quadra 800 Id */
+        ret = (ret & ~VIA1A_CPUID_MASK) | VIA1A_CPUID_Q800;
+        break;
+    }
+    return ret;
 }
 
 static void mos6522_q800_via1_write(void *opaque, hwaddr addr, uint64_t val,