[RFC,2/6] isa: rework ISA bus internals, and add ISA bus ops structure

diff --git a/hw/isa-bus.c b/hw/isa-bus.c
index 21b4b51..4757ff9 100644
--- a/hw/isa-bus.c
+++ b/hw/isa-bus.c
@@ -21,12 +21,9 @@ 
 #include "sysbus.h"
 #include "isa.h"
 
-struct ISABus {
-    BusState qbus;
-    qemu_irq *irqs;
-};
 static ISABus *isabus;
 target_phys_addr_t isa_mem_base = 0;
+static qemu_irq *isa_bus_default_irqs;
 
 static void isabus_dev_print(Monitor *mon, DeviceState *dev, int indent);
 static char *isabus_get_fw_dev_path(DeviceState *dev);
@@ -38,6 +35,24 @@  static struct BusInfo isa_bus_info = {
     .get_fw_dev_path = isabus_get_fw_dev_path,
 };
 
+static void isa_bus_default_set_irqs(ISABus *bus, qemu_irq *irqs)
+{
+    isa_bus_default_irqs = irqs;
+}
+
+static qemu_irq isa_bus_default_get_irq(ISABus *bus, int isairq)
+{
+    if (isairq < 0 || isairq > 15) {
+        hw_error("isa irq %d invalid", isairq);
+    }
+    return isa_bus_default_irqs[isairq];
+}
+
+static ISABusOps isa_bus_default_ops = {
+    .set_irqs = isa_bus_default_set_irqs,
+    .get_irq = isa_bus_default_get_irq,
+};
+
 ISABus *isa_bus_bridge_init(DeviceState *dev)
 {
     if (isabus) {
@@ -48,14 +63,29 @@  ISABus *isa_bus_bridge_init(DeviceState *dev)
         dev = qdev_create(NULL, "isabus-bridge");
         qdev_init_nofail(dev);
     }
-
-    isabus = FROM_QBUS(ISABus, qbus_create(&isa_bus_info, dev, NULL));
+    else {
+        isabus = FROM_QBUS(ISABus, qbus_create(&isa_bus_info, dev, NULL));
+        isabus->ops = &isa_bus_default_ops;
+    }
     return isabus;
 }
 
+void isa_bus_new(ISABus *bus, ISABusOps *ops, DeviceState *host)
+{
+    if (isabus) {
+        hw_error("Can't create a second ISA bus");
+    }
+    qbus_create_inplace(&bus->qbus, &isa_bus_info, host, NULL);
+    bus->ops = ops;
+    isabus = bus;
+}
+
 void isa_bus_irqs(qemu_irq *irqs)
 {
-    isabus->irqs = irqs;
+    if (!isabus || !isabus->ops->set_irqs) {
+        hw_error("Tried to set isa irqs with no isa bus present.");
+    }
+    isabus->ops->set_irqs(isabus, irqs);
 }
 
 /*
@@ -66,10 +96,10 @@  void isa_bus_irqs(qemu_irq *irqs)
  */
 qemu_irq isa_get_irq(int isairq)
 {
-    if (isairq < 0 || isairq > 15) {
-        hw_error("isa irq %d invalid", isairq);
+    if (!isabus || !isabus->ops->get_irq) {
+        hw_error("ISA bus invalid");
     }
-    return isabus->irqs[isairq];
+    return isabus->ops->get_irq(isabus, isairq);
 }
 
 void isa_init_irq(ISADevice *dev, qemu_irq *p, int isairq)
@@ -169,9 +199,15 @@  static void isabus_dev_print(Monitor *mon, DeviceState *dev, int indent)
     }
 }
 
+typedef struct {
+    SysBusDevice busdev;
+    ISABus bus;
+} ISABridgeSysBusState;
+
 static int isabus_bridge_init(SysBusDevice *dev)
 {
-    /* nothing */
+    ISABridgeSysBusState *isa = FROM_SYSBUS(ISABridgeSysBusState, dev);
+    isa_bus_new(&isa->bus, &isa_bus_default_ops, &dev->qdev);
     return 0;
 }
 
@@ -179,7 +215,7 @@  static SysBusDeviceInfo isabus_bridge_info = {
     .init = isabus_bridge_init,
     .qdev.name  = "isabus-bridge",
     .qdev.fw_name  = "isa",
-    .qdev.size  = sizeof(SysBusDevice),
+    .qdev.size  = sizeof(ISABridgeSysBusState),
     .qdev.no_user = 1,
 };
 
diff --git a/hw/isa.h b/hw/isa.h
index d6938f1..8c1583f 100644
--- a/hw/isa.h
+++ b/hw/isa.h
@@ -8,6 +8,7 @@ 
 #include "qdev.h"
 
 typedef struct ISABus ISABus;
+typedef struct ISABusOps ISABusOps;
 typedef struct ISADevice ISADevice;
 typedef struct ISADeviceInfo ISADeviceInfo;
 
@@ -25,7 +26,21 @@  struct ISADeviceInfo {
     isa_qdev_initfn init;
 };
 
+/* isa-bus.c */
+
+struct ISABus {
+    BusState qbus;
+    ISABusOps *ops;
+};
+
+struct ISABusOps {
+    void (*set_irqs)(ISABus *bus, qemu_irq *irqs);
+    qemu_irq (*get_irq)(ISABus *bus, int isairq);
+};
+
 ISABus *isa_bus_bridge_init(DeviceState *dev);
+
+void isa_bus_new(ISABus *bus, ISABusOps *ops, DeviceState *host);
 void isa_bus_irqs(qemu_irq *irqs);
 qemu_irq isa_get_irq(int isairq);
 void isa_init_irq(ISADevice *dev, qemu_irq *p, int isairq);