hw/pci: Have PCI_BUS implement TYPE_FW_CFG_DATA_GENERATOR_INTERFACE

The FW_CFG_DATA_GENERATOR interface allows any object to
produce a blob of data consumable by the fw_cfg device.
Implement that for PCI bus objects.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20241213133352.10915-5-philmd@linaro.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 1416ae202c..8844251ece 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -46,6 +46,7 @@
 #include "hw/pci/msix.h"
 #include "hw/hotplug.h"
 #include "hw/boards.h"
+#include "hw/nvram/fw_cfg.h"
 #include "qapi/error.h"
 #include "qemu/cutils.h"
 #include "pci-internal.h"
@@ -216,11 +217,41 @@ static uint16_t pcibus_numa_node(PCIBus *bus)
     return NUMA_NODE_UNASSIGNED;
 }
 
+static GByteArray *pci_bus_fw_cfg_gen_data(Object *obj, Error **errp)
+{
+    PCIBus *bus = PCI_BUS(obj);
+    GByteArray *byte_array;
+    uint64_t extra_hosts = 0;
+
+    if (!bus) {
+        return NULL;
+    }
+
+    QLIST_FOREACH(bus, &bus->child, sibling) {
+        /* look for expander root buses */
+        if (pci_bus_is_root(bus)) {
+            extra_hosts++;
+        }
+    }
+
+    if (!extra_hosts) {
+        return NULL;
+    }
+    extra_hosts = cpu_to_le64(extra_hosts);
+
+    byte_array = g_byte_array_new();
+    g_byte_array_append(byte_array,
+                        (const void *)&extra_hosts, sizeof(extra_hosts));
+
+    return byte_array;
+}
+
 static void pci_bus_class_init(ObjectClass *klass, void *data)
 {
     BusClass *k = BUS_CLASS(klass);
     PCIBusClass *pbc = PCI_BUS_CLASS(klass);
     ResettableClass *rc = RESETTABLE_CLASS(klass);
+    FWCfgDataGeneratorClass *fwgc = FW_CFG_DATA_GENERATOR_CLASS(klass);
 
     k->print_dev = pcibus_dev_print;
     k->get_dev_path = pcibus_get_dev_path;
@@ -232,6 +263,8 @@ static void pci_bus_class_init(ObjectClass *klass, void *data)
 
     pbc->bus_num = pcibus_num;
     pbc->numa_node = pcibus_numa_node;
+
+    fwgc->get_data = pci_bus_fw_cfg_gen_data;
 }
 
 static const TypeInfo pci_bus_info = {
@@ -240,6 +273,10 @@ static const TypeInfo pci_bus_info = {
     .instance_size = sizeof(PCIBus),
     .class_size = sizeof(PCIBusClass),
     .class_init = pci_bus_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_FW_CFG_DATA_GENERATOR_INTERFACE },
+        { }
+    }
 };
 
 static const TypeInfo cxl_interface_info = {