isa: add isa_address_space()

A helper that returns the address space used by ISA devices.  Useful
for getting rid of isa_mem_base, multiple ISA buses, or ISA buses behind
bridges.
Signed-off-by: NAvi Kivity <avi@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/isa-bus.c

@@ -20,6 +20,7 @@
 #include "monitor.h"
 #include "sysbus.h"
 #include "isa.h"
+#include "exec-memory.h"
 
 struct ISABus {
     BusState qbus;
@@ -202,4 +203,9 @@ static char *isabus_get_fw_dev_path(DeviceState *dev)
     return strdup(path);
 }
 
+MemoryRegion *isa_address_space(ISADevice *dev)
+{
+    return get_system_memory();
+}
+
 device_init(isabus_register_devices)

hw/isa.h

@@ -32,6 +32,7 @@ void isa_init_irq(ISADevice *dev, qemu_irq *p, int isairq);
 void isa_init_ioport(ISADevice *dev, uint16_t ioport);
 void isa_init_ioport_range(ISADevice *dev, uint16_t start, uint16_t length);
 void isa_qdev_register(ISADeviceInfo *info);
+MemoryRegion *isa_address_space(ISADevice *dev);
 ISADevice *isa_create(const char *name);
 ISADevice *isa_try_create(const char *name);
 ISADevice *isa_create_simple(const char *name);