tests/qtest: Add a function that checks whether a device is available

Devices might not always be compiled into the QEMU target binaries.
We already have the libqos framework that is good for handling such
situations, but some of the qtests are not a real good fit for the
libqos framework. Let's add a qtest_has_device() function for such
tests instead.

Message-Id: <20211220081054.151515-2-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/qtest/libqos/libqtest.h

@@ -718,6 +718,14 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine),
  */
 bool qtest_has_machine(const char *machine);
 
+/**
+ * qtest_has_device:
+ * @device: The device to look for
+ *
+ * Returns: true if the device is available in the target binary.
+ */
+bool qtest_has_device(const char *device);
+
 /**
  * qtest_qmp_device_add_qdict:
  * @qts: QTestState instance to operate on

tests/qtest/libqtest.c

@@ -1418,6 +1418,50 @@ bool qtest_has_machine(const char *machine)
     return false;
 }
 
+bool qtest_has_device(const char *device)
+{
+    static QList *list;
+    const QListEntry *p;
+    QObject *qobj;
+    QString *qstr;
+    QDict *devinfo;
+    int idx;
+
+    if (!list) {
+        QDict *resp;
+        QDict *args;
+        QTestState *qts = qtest_init("-machine none");
+
+        args = qdict_new();
+        qdict_put_bool(args, "abstract", false);
+        qdict_put_str(args, "implements", "device");
+
+        resp = qtest_qmp(qts, "{'execute': 'qom-list-types', 'arguments': %p }",
+                         args);
+        g_assert(qdict_haskey(resp, "return"));
+        list = qdict_get_qlist(resp, "return");
+        qobject_ref(list);
+        qobject_unref(resp);
+
+        qtest_quit(qts);
+    }
+
+    for (p = qlist_first(list), idx = 0; p; p = qlist_next(p), idx++) {
+        devinfo = qobject_to(QDict, qlist_entry_obj(p));
+        g_assert(devinfo);
+
+        qobj = qdict_get(devinfo, "name");
+        g_assert(qobj);
+        qstr = qobject_to(QString, qobj);
+        g_assert(qstr);
+        if (g_str_equal(qstring_get_str(qstr), device)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 /*
  * Generic hot-plugging test via the device_add QMP commands.
  */