hw/acpi: move object_resolve_type_unambiguous to core QOM

object_resolve_type_unambiguous provides a useful functionality, that
is currently emulated for example by usb_bus_find().  Move it to core
code and add error reporting for increased generality.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240223124406.234509-2-pbonzini@redhat.com>
[PMD: Fixed style]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/i386/acpi-build.c

@@ -192,21 +192,10 @@ static void init_common_fadt_data(MachineState *ms, Object *o,
     *data = fadt;
 }
 
-static Object *object_resolve_type_unambiguous(const char *typename)
-{
-    bool ambig;
-    Object *o = object_resolve_path_type("", typename, &ambig);
-
-    if (ambig || !o) {
-        return NULL;
-    }
-    return o;
-}
-
 static void acpi_get_pm_info(MachineState *machine, AcpiPmInfo *pm)
 {
-    Object *piix = object_resolve_type_unambiguous(TYPE_PIIX4_PM);
+    Object *piix = object_resolve_type_unambiguous(TYPE_PIIX4_PM, NULL);
-    Object *lpc = object_resolve_type_unambiguous(TYPE_ICH9_LPC_DEVICE);
+    Object *lpc = object_resolve_type_unambiguous(TYPE_ICH9_LPC_DEVICE, NULL);
     Object *obj = piix ? piix : lpc;
     QObject *o;
     pm->cpu_hp_io_base = 0;
@@ -1428,8 +1417,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
            AcpiPmInfo *pm, AcpiMiscInfo *misc,
            Range *pci_hole, Range *pci_hole64, MachineState *machine)
 {
-    Object *i440fx = object_resolve_type_unambiguous(TYPE_I440FX_PCI_HOST_BRIDGE);
+    Object *i440fx = object_resolve_type_unambiguous(TYPE_I440FX_PCI_HOST_BRIDGE,
-    Object *q35 = object_resolve_type_unambiguous(TYPE_Q35_HOST_DEVICE);
+                                                     NULL);
+    Object *q35 = object_resolve_type_unambiguous(TYPE_Q35_HOST_DEVICE, NULL);
     CrsRangeEntry *entry;
     Aml *dsdt, *sb_scope, *scope, *dev, *method, *field, *pkg, *crs;
     CrsRangeSet crs_range_set;

include/qom/object.h

@@ -1550,6 +1550,19 @@ Object *object_resolve_path(const char *path, bool *ambiguous);
 Object *object_resolve_path_type(const char *path, const char *typename,
                                  bool *ambiguous);
 
+/**
+ * object_resolve_type_unambiguous:
+ * @typename: the type to look for
+ * @errp: pointer to error object
+ *
+ * Return the only object in the QOM tree of type @typename.
+ * If no match or more than one match is found, an error is
+ * returned.
+ *
+ * Returns: The matched object or NULL on path lookup failure.
+ */
+Object *object_resolve_type_unambiguous(const char *typename, Error **errp);
+
 /**
  * object_resolve_path_at:
  * @parent: the object in which to resolve the path

qom/object.c

@@ -2229,6 +2229,22 @@ Object *object_resolve_path_at(Object *parent, const char *path)
     return object_resolve_abs_path(parent, parts, TYPE_OBJECT);
 }
 
+Object *object_resolve_type_unambiguous(const char *typename, Error **errp)
+{
+    bool ambig;
+    Object *o = object_resolve_path_type("", typename, &ambig);
+
+    if (ambig) {
+        error_setg(errp, "More than one object of type %s", typename);
+        return NULL;
+    }
+    if (!o) {
+        error_setg(errp, "No object found of type %s", typename);
+        return NULL;
+    }
+    return o;
+}
+
 typedef struct StringProperty
 {
     char *(*get)(Object *, Error **);