[PATCH 04/20] nubus: use bitmap to manage available slots

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

Convert nubus_device_realize() to use a bitmap to manage available slots to allow
for future Nubus devices to be plugged into arbitrary slots from the command line.

Update mac_nubus_bridge_init() to only allow slots 0x9 to 0xe on a Macintosh
machines as documented in "Desigining Cards and Drivers for the Macintosh Family".

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/nubus/mac-nubus-bridge.c |  3 +++
 hw/nubus/nubus-bus.c        |  2 +-
 hw/nubus/nubus-device.c     | 33 +++++++++++++++++++++++++++------
 include/hw/nubus/nubus.h    |  4 ++--
 4 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/hw/nubus/mac-nubus-bridge.c b/hw/nubus/mac-nubus-bridge.c
index 7c329300b8..6e78f4c0b3 100644
--- a/hw/nubus/mac-nubus-bridge.c
+++ b/hw/nubus/mac-nubus-bridge.c
@@ -18,6 +18,9 @@ static void mac_nubus_bridge_init(Object *obj)
 
     s->bus = NUBUS_BUS(qbus_create(TYPE_NUBUS_BUS, DEVICE(s), NULL));
 
+    /* Macintosh only has slots 0x9 to 0xe available */
+    s->bus->slot_available_mask = 0x7e00;
+
     sysbus_init_mmio(sbd, &s->bus->super_slot_io);
     sysbus_init_mmio(sbd, &s->bus->slot_io);
 }
diff --git a/hw/nubus/nubus-bus.c b/hw/nubus/nubus-bus.c
index 5c13452308..f6d3655f51 100644
--- a/hw/nubus/nubus-bus.c
+++ b/hw/nubus/nubus-bus.c
@@ -84,7 +84,7 @@ static void nubus_init(Object *obj)
                           nubus, "nubus-slots",
                           NUBUS_SLOT_NB * NUBUS_SLOT_SIZE);
 
-    nubus->current_slot = NUBUS_FIRST_SLOT;
+    nubus->slot_available_mask = 0xffff;
 }
 
 static void nubus_class_init(ObjectClass *oc, void *data)
diff --git a/hw/nubus/nubus-device.c b/hw/nubus/nubus-device.c
index c1832f73da..f9f614cc01 100644
--- a/hw/nubus/nubus-device.c
+++ b/hw/nubus/nubus-device.c
@@ -160,14 +160,35 @@ static void nubus_device_realize(DeviceState *dev, Error **errp)
     NubusDevice *nd = NUBUS_DEVICE(dev);
     char *name;
     hwaddr slot_offset;
-
-    if (nubus->current_slot < NUBUS_FIRST_SLOT ||
-            nubus->current_slot > NUBUS_LAST_SLOT) {
-        error_setg(errp, "Cannot register nubus card, not enough slots");
-        return;
+    uint16_t s;
+
+    if (nd->slot == -1) {
+        /* No slot specified, find first available free slot */
+        s = ctz32(nubus->slot_available_mask);
+        if (s != 32) {
+            nd->slot = s;
+        } else {
+            error_setg(errp, "Cannot register nubus card, no free slot "
+                             "available");
+            return;
+        }
+    } else {
+        /* Slot specified, make sure the slot is available */
+        if (nd->slot < NUBUS_FIRST_SLOT || nd->slot > NUBUS_LAST_SLOT) {
+            error_setg(errp, "Cannot register nubus card, slot must be "
+                             "between %d and %d", NUBUS_FIRST_SLOT,
+                             NUBUS_LAST_SLOT);
+            return;
+        }
+
+        if (!(nubus->slot_available_mask & (1UL << nd->slot))) {
+            error_setg(errp, "Cannot register nubus card, slot %d is "
+                             "unavailable or already occupied", nd->slot);
+            return;
+        }
     }
 
-    nd->slot = nubus->current_slot++;
+    nubus->slot_available_mask &= ~(1UL << nd->slot);
 
     /* Super */
     slot_offset = (nd->slot - 6) * NUBUS_SUPER_SLOT_SIZE;
diff --git a/include/hw/nubus/nubus.h b/include/hw/nubus/nubus.h
index 357f621d15..8ff4736259 100644
--- a/include/hw/nubus/nubus.h
+++ b/include/hw/nubus/nubus.h
@@ -19,7 +19,7 @@
 #define NUBUS_SLOT_SIZE       0x01000000
 #define NUBUS_SLOT_NB         0xF
 
-#define NUBUS_FIRST_SLOT      0x9
+#define NUBUS_FIRST_SLOT      0x0
 #define NUBUS_LAST_SLOT       0xF
 
 #define TYPE_NUBUS_DEVICE "nubus-device"
@@ -36,7 +36,7 @@ struct NubusBus {
     MemoryRegion super_slot_io;
     MemoryRegion slot_io;
 
-    int current_slot;
+    uint32_t slot_available_mask;
 };
 
 struct NubusDevice {
-- 
2.20.1