pci: add pci_address_space_io()

Returns the I/O address space.  Useful for implementing
PCI-ISA bridge devices.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Avi Kivity <avi@redhat.com>

hw/pci.c

diff --git a/hw/pci.c b/hw/pci.c
index 5c4f071..749e8d8 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -2124,3 +2124,8 @@
 {
     return dev->bus->address_space_mem;
 }
+
+MemoryRegion *pci_address_space_io(PCIDevice *dev)
+{
+    return dev->bus->address_space_io;
+}

hw/pci.h

diff --git a/hw/pci.h b/hw/pci.h
index 7b62df1..86a81c8 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -218,6 +218,7 @@
 void pci_device_save(PCIDevice *s, QEMUFile *f);
 int pci_device_load(PCIDevice *s, QEMUFile *f);
 MemoryRegion *pci_address_space(PCIDevice *dev);
+MemoryRegion *pci_address_space_io(PCIDevice *dev);
 
 typedef void (*pci_set_irq_fn)(void *opaque, int irq_num, int level);
 typedef int (*pci_map_irq_fn)(PCIDevice *pci_dev, int irq_num);