[1/4] rng: add RndBackend abstract object class

diff --git a/Makefile.objs b/Makefile.objs
index 74110dd..cb481b5 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -94,6 +94,8 @@  common-obj-y += qemu-timer.o qemu-timer-common.o
 
 common-obj-$(CONFIG_SLIRP) += slirp/
 
+common-obj-y += backends/
+
 ######################################################################
 # libuser
 
diff --git a/backends/Makefile.objs b/backends/Makefile.objs
new file mode 100644
index 0000000..06e08c7
--- /dev/null
+++ b/backends/Makefile.objs
@@ -0,0 +1 @@ 
+common-obj-y += rng.o
diff --git a/backends/rng.c b/backends/rng.c
new file mode 100644
index 0000000..06f2611
--- /dev/null
+++ b/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);
diff --git a/include/qemu/rng.h b/include/qemu/rng.h
new file mode 100644
index 0000000..7e9d672
--- /dev/null
+++ b/include/qemu/rng.h
@@ -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.
+ */
+
+#ifndef QEMU_RNG_H
+#define QEMU_RNG_H
+
+#include "qemu/object.h"
+#include "qemu-common.h"
+#include "error.h"
+
+#define TYPE_RNG_BACKEND "rng-backend"
+#define RNG_BACKEND(obj) \
+    OBJECT_CHECK(RngBackend, (obj), TYPE_RNG_BACKEND)
+#define RNG_BACKEND_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(RngBackendClass, (obj), TYPE_RNG_BACKEND)
+#define RNG_BACKEND_CLASS(klass) \
+    OBJECT_CLASS_CHECK(RngBackendClass, (klass), TYPE_RNG_BACKEND)
+
+typedef struct RngBackendClass RngBackendClass;
+typedef struct RngBackend RngBackend;
+
+typedef void (EntropyReceiveFunc)(void *opaque,
+                                  const void *data,
+                                  size_t size);
+
+struct RngBackendClass
+{
+    ObjectClass parent_class;
+
+    void (*request_entropy)(RngBackend *s, size_t size,
+                            EntropyReceiveFunc *recieve_entropy, void *opaque);
+    void (*cancel_requests)(RngBackend *s);
+
+    void (*opened)(RngBackend *s, Error **errp);
+};
+
+struct RngBackend
+{
+    Object parent;
+
+    /*< protected >*/
+    bool opened;
+};
+
+/**
+ * rng_backend_request_entropy:
+ * @s: the backend to request entropy from
+ * @size: the number of bytes of data to request
+ * @receive_entropy: a function to be invoked when entropy is available
+ * @opaque: data that should be passed to @receive_entropy
+ *
+ * This function is used by the front-end to request entropy from an entropy
+ * source.  This function can be called multiple times before @receive_entropy
+ * is invoked with different values of @receive_entropy and @opaque.  The
+ * backend will queue each request and handle appropriate.
+ *
+ * The backend does not need to pass the full amount of data to @receive_entropy
+ * but will pass at a value greater than 0.
+ */
+void rng_backend_request_entropy(RngBackend *s, size_t size,
+                                 EntropyReceiveFunc *receive_entropy,
+                                 void *opaque);
+
+/**
+ * rng_backend_cancel_requests:
+ * @s: the backend to cancel all pending requests in
+ *
+ * Cancels all pending requests submitted by @rng_backend_request_entropy.  This
+ * should be used by a device during reset or in preparation for live migration
+ * to stop tracking any request.
+ */
+void rng_backend_cancel_requests(RngBackend *s);
+
+/**
+ * rng_backend_open:
+ * @s: the backend to open
+ * @errp: a pointer to return the #Error object if an error occurs.
+ *
+ * This function will open the backend if it is not already open.  Calling this
+ * function on an already opened backend will not result in an error.
+ */ 
+void rng_backend_open(RngBackend *s, Error **errp);
+
+#endif