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>

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