[Xen-devel] [PATCH 3/6] Network acceleration improvements

[Kieran Mansley <kmansley@xxxxxxxxxxxxxx>]

Signed-off-by: Kieran Mansley <kmansley@xxxxxxxxxxxxxx> 

Add version number to API between netback and accel plugin

diff -r 330deb0c6935 drivers/xen/netback/accel.c
--- a/drivers/xen/netback/accel.c       Wed Oct 03 13:30:20 2007 +0100
+++ b/drivers/xen/netback/accel.c       Wed Oct 03 13:32:27 2007 +0100
@@ -103,18 +103,35 @@ static int netback_accelerator_tell_back
  * Entry point for an netback accelerator plugin module.  Called to
  * advertise its presence, and connect to any suitable backends.
  */
-void netback_connect_accelerator(int id, const char *eth_name, 
-                                struct netback_accel_hooks *hooks)
-{
-       struct netback_accelerator *new_accelerator = 
+int netback_connect_accelerator(unsigned version, int id, const char 
*eth_name, 
+                               struct netback_accel_hooks *hooks)
+{
+       struct netback_accelerator *new_accelerator;
+       unsigned eth_name_len, flags;
+
+       if (version != NETBACK_ACCEL_VERSION) {
+               if (version > NETBACK_ACCEL_VERSION) {
+                       /* Caller has higher version number, leave it
+                          up to them to decide whether to continue.
+                          They can recall with a lower number if
+                          they're happy to be compatible with us */
+                       return NETBACK_ACCEL_VERSION;
+               } else {
+                       /* We have a more recent version than caller.
+                          Currently reject, but may in future be able
+                          to be backwardly compatible */
+                       return -EPROTO;
+               }
+       }
+
+       new_accelerator = 
                kmalloc(sizeof(struct netback_accelerator), GFP_KERNEL);
-       unsigned eth_name_len, flags;
-
        if (!new_accelerator) {
                DPRINTK("%s: failed to allocate memory for accelerator\n",
                        __FUNCTION__);
-               return;
-       }
+               return -ENOMEM;
+       }
+
 
        new_accelerator->id = id;
        
@@ -124,7 +141,7 @@ void netback_connect_accelerator(int id,
                DPRINTK("%s: failed to allocate memory for eth_name string\n",
                        __FUNCTION__);
                kfree(new_accelerator);
-               return;
+               return -ENOMEM;
        }
        strlcpy(new_accelerator->eth_name, eth_name, eth_name_len);
        
@@ -139,6 +156,8 @@ void netback_connect_accelerator(int id,
        /* tell existing backends about new plugin */
        xenbus_for_each_backend(new_accelerator, 
                                netback_accelerator_tell_backend);
+
+       return 0;
 
 }
 EXPORT_SYMBOL_GPL(netback_connect_accelerator);
diff -r 330deb0c6935 drivers/xen/netback/common.h
--- a/drivers/xen/netback/common.h      Wed Oct 03 13:30:20 2007 +0100
+++ b/drivers/xen/netback/common.h      Wed Oct 03 13:36:10 2007 +0100
@@ -149,9 +149,16 @@ struct backend_info {
        struct netback_accelerator *accelerator;
 };
 
-/* Connect an accelerator plugin module to netback */
-extern void netback_connect_accelerator(int id, const char *eth_name, 
-                                       struct netback_accel_hooks *hooks);
+#define NETBACK_ACCEL_VERSION 0x00010000
+
+/* 
+ * Connect an accelerator plugin module to netback.  Returns zero on
+ * success, < 0 on error, > 0 (with highest version number supported)
+ * if version mismatch.
+ */
+extern int netback_connect_accelerator(unsigned version,
+                                      int id, const char *eth_name, 
+                                      struct netback_accel_hooks *hooks);
 /* Disconnect a previously connected accelerator plugin module */
 extern void netback_disconnect_accelerator(int id, const char *eth_name);

Attachment: netback_version
Description: Text document

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