From: David Woodhouse <dwmw@amazon.co.uk>

Most code which directly accesses nd_table[] and nb_nics uses them for
one of two things. Either "I have created a NIC device and I'd like a
configuration for it", or "I will create a NIC device *if* there is a
configuration for it".  With some variants on the theme around whether
they actually *check* if the model specified in the configuration is
the right one.

Provide functions which perform both of those, allowing platforms to
be a little more consistent and as a step towards making nd_table[]
and nb_nics private to the net code.

Also export the qemu_find_nic_info() helper, as some platforms have
special cases they need to handle.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---
 include/net/net.h |  7 ++++++-
 net/net.c         | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/include/net/net.h b/include/net/net.h
index 2fb1c9181c..56be694c75 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -205,7 +205,12 @@ int qemu_show_nic_models(const char *arg, const char *const *models);
 void qemu_check_nic_model(NICInfo *nd, const char *model);
 int qemu_find_nic_model(NICInfo *nd, const char * const *models,
                         const char *default_model);
-
+NICInfo *qemu_find_nic_info(const char *typename, bool match_default,
+                            const char *alias);
+bool qemu_configure_nic_device(DeviceState *dev, bool match_default,
+                               const char *alias);
+DeviceState *qemu_create_nic_device(const char *typename, bool match_default,
+                                    const char *alias);
 void print_net_client(Monitor *mon, NetClientState *nc);
 void net_socket_rs_init(SocketReadState *rs,
                         SocketReadStateFinalize *finalize,
diff --git a/net/net.c b/net/net.c
index bbe33da176..f8b4973a1e 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1072,6 +1072,57 @@ static int net_init_nic(const Netdev *netdev, const char *name,
     return idx;
 }
 
+NICInfo *qemu_find_nic_info(const char *typename, bool match_default,
+                            const char *alias)
+{
+    NICInfo *nd;
+    int i;
+
+    for (i = 0; i < nb_nics; i++) {
+        nd = &nd_table[i];
+
+        if (!nd->used || nd->instantiated) {
+            continue;
+        }
+
+        if ((match_default && !nd->model) || !g_strcmp0(nd->model, typename)
+            || (alias && !g_strcmp0(nd->model, alias))) {
+            return nd;
+        }
+    }
+    return NULL;
+}
+
+
+/* "I have created a device. Please configure it if you can" */
+bool qemu_configure_nic_device(DeviceState *dev, bool match_default,
+                               const char *alias)
+{
+    NICInfo *nd = qemu_find_nic_info(object_get_typename(OBJECT(dev)),
+                                     match_default, alias);
+
+    if (nd) {
+        qdev_set_nic_properties(dev, nd);
+        return true;
+    }
+    return false;
+}
+
+/* "Please create a device, if you have a configuration for it" */
+DeviceState *qemu_create_nic_device(const char *typename, bool match_default,
+                                    const char *alias)
+{
+    NICInfo *nd = qemu_find_nic_info(typename, match_default, alias);
+    DeviceState *dev;
+
+    if (!nd) {
+        return NULL;
+    }
+
+    dev = qdev_new(typename);
+    qdev_set_nic_properties(dev, nd);
+    return dev;
+}
 
 static int (* const net_client_init_fun[NET_CLIENT_DRIVER__MAX])(
     const Netdev *netdev,
-- 
2.41.0