macfb: increase number of registers saved in MacfbState

The MacOS toolbox ROM accesses a number of addresses between 0x0 and 0x200 during
initialisation and resolution changes. Whilst the function of many of these
registers is unknown, it is worth the minimal cost of saving these extra values as
part of migration to help future-proof the migration stream for the q800 machine
as it starts to stabilise.

Note this is a migration break, but since there are upcoming incompatible changes
for the q800 machine (and migration does not even succeed without these patches)
then this is not an issue.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220305155530.9265-4-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

hw/display/macfb.c

@@ -537,6 +537,10 @@ static uint64_t macfb_ctrl_read(void *opaque,
     case DAFB_MODE_SENSE:
         val = macfb_sense_read(s);
         break;
+    default:
+        if (addr < MACFB_CTRL_TOPADDR) {
+            val = s->regs[addr >> 2];
+        }
     }
 
     trace_macfb_ctrl_read(addr, val, size);
@@ -592,6 +596,10 @@ static void macfb_ctrl_write(void *opaque,
             macfb_invalidate_display(s);
         }
         break;
+    default:
+        if (addr < MACFB_CTRL_TOPADDR) {
+            s->regs[addr >> 2] = val;
+        }
     }
 
     trace_macfb_ctrl_write(addr, val, size);

include/hw/display/macfb.h

@@ -48,7 +48,8 @@ typedef struct MacFbMode {
     uint32_t offset;
 } MacFbMode;
 
-#define MACFB_NUM_REGS      8
+#define MACFB_CTRL_TOPADDR  0x200
+#define MACFB_NUM_REGS      (MACFB_CTRL_TOPADDR / sizeof(uint32_t))
 
 typedef struct MacfbState {
     MemoryRegion mem_vram;