Backend net driver acceleration

diff -r 6362a643064a linux-2.6-xen-sparse/drivers/xen/netback/common.h
--- a/linux-2.6-xen-sparse/drivers/xen/netback/common.h	Thu Mar 08 13:45:57 2007 +0000
+++ b/linux-2.6-xen-sparse/drivers/xen/netback/common.h	Thu Mar 08 13:46:01 2007 +0000
@@ -114,6 +114,31 @@ typedef struct netif_st {
 #define netback_carrier_off(netif)	((netif)->carrier = 0)
 #define netback_carrier_ok(netif)	((netif)->carrier)
 
+
+#include <xen/xenbus.h>
+struct netback_accel_hooks {
+        int  (*probe)(struct xenbus_device *dev);
+};
+
+/* Structure to track the state of a netback accelerator plugin */
+struct netback_accelerator {
+        int id;
+        char *frontend;
+        struct netback_accel_hooks *hooks;
+        struct netback_accelerator *next;
+};
+extern void netback_connect_accelerator(int id, const char *frontend, 
+                                        struct netback_accel_hooks *hooks);
+
+struct backend_info {
+	struct xenbus_device *dev;
+	netif_t *netif;
+	enum xenbus_state frontend_state;
+        void *netback_accel_priv;
+        struct netback_accelerator *accelerator;
+};
+
+
 #define NET_TX_RING_SIZE __RING_SIZE((netif_tx_sring_t *)0, PAGE_SIZE)
 #define NET_RX_RING_SIZE __RING_SIZE((netif_rx_sring_t *)0, PAGE_SIZE)
 
diff -r 6362a643064a linux-2.6-xen-sparse/drivers/xen/netback/xenbus.c
--- a/linux-2.6-xen-sparse/drivers/xen/netback/xenbus.c	Thu Mar 08 13:45:57 2007 +0000
+++ b/linux-2.6-xen-sparse/drivers/xen/netback/xenbus.c	Thu Mar 08 13:46:01 2007 +0000
@@ -1,6 +1,7 @@
 /*  Xenbus code for netif backend
     Copyright (C) 2005 Rusty Russell <rusty@xxxxxxxxxxxxxxx>
     Copyright (C) 2005 XenSource Ltd
+    Copyright (c) 2007 Solarflare Communications, Inc.
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -28,11 +29,52 @@
     printk("netback/xenbus (%s:%d) " fmt ".\n", __FUNCTION__, __LINE__, ##args)
 #endif
 
-struct backend_info {
-	struct xenbus_device *dev;
-	netif_t *netif;
-	enum xenbus_state frontend_state;
-};
+static struct netback_accelerator *accelerators = NULL;
+
+static int netback_accelerator_tell_backend(struct device *dev, void *arg){
+        struct netback_accelerator *accelerator = 
+                (struct netback_accelerator *)arg;
+        struct xenbus_device *xendev = to_xenbus_device(dev);
+
+        if(!strcmp("vif", xendev->devicetype)){
+                struct backend_info *be = xendev->dev.driver_data;
+
+                be->accelerator = accelerator;
+                be->accelerator->hooks->probe(xendev);
+        }
+        return 0;
+}
+
+
+static void 
+netback_accelerator_tell_backends(struct netback_accelerator *accelerator)
+{
+        xenbus_for_each_backend(accelerator, netback_accelerator_tell_backend);
+}
+
+
+void netback_connect_accelerator(int id, const char *frontend, 
+                                 struct netback_accel_hooks *hooks)
+{
+        struct netback_accelerator *new_accelerator = 
+                kzalloc(sizeof(struct netback_accelerator), GFP_KERNEL);
+
+        if(new_accelerator){
+                new_accelerator->id = id;
+                new_accelerator->frontend = kzalloc(strlen(frontend), GFP_KERNEL);
+                strcpy(new_accelerator->frontend, frontend);
+                new_accelerator->hooks = hooks;
+                
+                new_accelerator->next = accelerators;
+                accelerators = new_accelerator;
+                
+                /* tell existing backends about new plugin */
+                netback_accelerator_tell_backends(new_accelerator);
+        }
+}
+EXPORT_SYMBOL_GPL(netback_connect_accelerator);
+
 
 static int connect_rings(struct backend_info *);
 static void connect(struct backend_info *);
@@ -119,6 +161,12 @@ static int netback_probe(struct xenbus_d
 		xenbus_dev_fatal(dev, err, "completing transaction");
 		goto fail;
 	}
+
+        be->accelerator = accelerators;
+        if(be->accelerator && be->accelerator->hooks
+           && be->accelerator->hooks->probe){
+                be->accelerator->hooks->probe(dev);
+        }
 
 	err = xenbus_switch_state(dev, XenbusStateInitWait);
 	if (err)