rng: add RndBackend abstract object class

This is the backend used by devices that need to request entropy.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

backends/rng.c

@@ -0,0 +1,93 @@
+/*
+ * QEMU Random Number Generator Backend
+ *
+ * Copyright IBM, Corp. 2012
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/rng.h"
+#include "qerror.h"
+
+void rng_backend_request_entropy(RngBackend *s, size_t size,
+                                 EntropyReceiveFunc *receive_entropy,
+                                 void *opaque)
+{
+    RngBackendClass *k = RNG_BACKEND_GET_CLASS(s);
+
+    if (k->request_entropy) {
+        k->request_entropy(s, size, receive_entropy, opaque);
+    }
+}
+
+void rng_backend_cancel_requests(RngBackend *s)
+{
+    RngBackendClass *k = RNG_BACKEND_GET_CLASS(s);
+
+    if (k->cancel_requests) {
+        k->cancel_requests(s);
+    }
+}
+
+static bool rng_backend_prop_get_opened(Object *obj, Error **errp)
+{
+    RngBackend *s = RNG_BACKEND(obj);
+
+    return s->opened;
+}
+
+void rng_backend_open(RngBackend *s, Error **errp)
+{
+    object_property_set_bool(OBJECT(s), true, "opened", errp);
+}
+
+static void rng_backend_prop_set_opened(Object *obj, bool value, Error **errp)
+{
+    RngBackend *s = RNG_BACKEND(obj);
+    RngBackendClass *k = RNG_BACKEND_GET_CLASS(s);
+
+    if (value == s->opened) {
+        return;
+    }
+
+    if (!value && s->opened) {
+        error_set(errp, QERR_PERMISSION_DENIED);
+        return;
+    }
+
+    if (k->opened) {
+        k->opened(s, errp);
+    }
+
+    if (!error_is_set(errp)) {
+        s->opened = value;
+    }
+}
+
+static void rng_backend_init(Object *obj)
+{
+    object_property_add_bool(obj, "opened",
+                             rng_backend_prop_get_opened,
+                             rng_backend_prop_set_opened,
+                             NULL);
+}
+
+static TypeInfo rng_backend_info = {
+    .name = TYPE_RNG_BACKEND,
+    .parent = TYPE_OBJECT,
+    .instance_size = sizeof(RngBackend),
+    .instance_init = rng_backend_init,
+    .class_size = sizeof(RngBackendClass),
+    .abstract = true,
+};
+
+static void register_types(void)
+{
+    type_register_static(&rng_backend_info);
+}
+
+type_init(register_types);