pci/pcie_port: Add pci_find_port_by_pn()

Simple function to search a PCIBus to find a port by
it's port number.

CXL interleave decoding uses the port number as a target
so it is necessary to locate the port when doing interleave
decoding.

Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220429144110.25167-31-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pcie_port.c

@@ -136,6 +136,31 @@ static void pcie_port_class_init(ObjectClass *oc, void *data)
     device_class_set_props(dc, pcie_port_props);
 }
 
+PCIDevice *pcie_find_port_by_pn(PCIBus *bus, uint8_t pn)
+{
+    int devfn;
+
+    for (devfn = 0; devfn < ARRAY_SIZE(bus->devices); devfn++) {
+        PCIDevice *d = bus->devices[devfn];
+        PCIEPort *port;
+
+        if (!d || !pci_is_express(d) || !d->exp.exp_cap) {
+            continue;
+        }
+
+        if (!object_dynamic_cast(OBJECT(d), TYPE_PCIE_PORT)) {
+            continue;
+        }
+
+        port = PCIE_PORT(d);
+        if (port->port == pn) {
+            return d;
+        }
+    }
+
+    return NULL;
+}
+
 static const TypeInfo pcie_port_type_info = {
     .name = TYPE_PCIE_PORT,
     .parent = TYPE_PCI_BRIDGE,

include/hw/pci/pcie_port.h

@@ -39,6 +39,8 @@ struct PCIEPort {
 
 void pcie_port_init_reg(PCIDevice *d);
 
+PCIDevice *pcie_find_port_by_pn(PCIBus *bus, uint8_t pn);
+
 #define TYPE_PCIE_SLOT "pcie-slot"
 OBJECT_DECLARE_SIMPLE_TYPE(PCIESlot, PCIE_SLOT)