From 500054f161c29ff9db125c0b872809191ad6920b Mon Sep 17 00:00:00 2001
From: Anthony Liguori <aliguori@us.ibm.com>
Date: Fri, 26 Oct 2012 12:05:49 -0500
Subject: [PATCH] virtio-rng-pci: create a default backend if none exists

This allows you to specify:

  $ qemu -device virtio-rng-pci

And things will Just Work with a reasonable default.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 hw/virtio-pci.c | 13 +++++++++++++
 hw/virtio-rng.h |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index f90296d..71f4fb5 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -857,6 +857,19 @@ static int virtio_rng_init_pci(PCIDevice *pci_dev)
     VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
     VirtIODevice *vdev;
 
+    if (proxy->rng.rng == NULL) {
+        proxy->rng.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
+
+        object_property_add_child(OBJECT(pci_dev),
+                                  "default-backend",
+                                  OBJECT(proxy->rng.default_backend),
+                                  NULL);
+
+        object_property_set_link(OBJECT(pci_dev),
+                                 OBJECT(proxy->rng.default_backend),
+                                 "rng", NULL);
+    }
+
     vdev = virtio_rng_init(&pci_dev->qdev, &proxy->rng);
     if (!vdev) {
         return -1;
diff --git a/hw/virtio-rng.h b/hw/virtio-rng.h
index 7324d0a..f42d748 100644
--- a/hw/virtio-rng.h
+++ b/hw/virtio-rng.h
@@ -13,6 +13,7 @@
 #define _QEMU_VIRTIO_RNG_H
 
 #include "qemu/rng.h"
+#include "qemu/rng-random.h"
 
 /* The Virtio ID for the virtio rng device */
 #define VIRTIO_ID_RNG    4
@@ -21,6 +22,7 @@ struct VirtIORNGConf {
     RngBackend *rng;
     uint64_t max_bytes;
     uint32_t period_ms;
+    RndRandom *default_backend;
 };
 
 #endif
-- 
2.7.4