net: Add init_dummy_netdev() and fix EMAC driver using it

This adds an init_dummy_netdev() function that gets a network device
structure (allocation and lifetime entirely under caller's control) and
initialize the minimum amount of fields so it can be used to schedule
NAPI polls without registering a full blown interface. This is to be
used by drivers that need to tie several hardware interfaces to a single
NAPI poll scheduler due to HW limitations.

It also updates the ibm_newemac driver to use that, this fixing the
oops on 2.6.29 due to passing NULL as "dev" to netif_napi_add()

Symbol is exported GPL only a I don't think we want binary drivers doing
that sort of acrobatics (if we want them at all).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Tested-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 60377b6c0a80..8d675975d85b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4431,6 +4431,45 @@ err_uninit:
 }
 
 /**
+ *      init_dummy_netdev       - init a dummy network device for NAPI
+ *      @dev: device to init
+ *
+ *      This takes a network device structure and initialize the minimum
+ *      amount of fields so it can be used to schedule NAPI polls without
+ *      registering a full blown interface. This is to be used by drivers
+ *      that need to tie several hardware interfaces to a single NAPI
+ *      poll scheduler due to HW limitations.
+ */
+int init_dummy_netdev(struct net_device *dev)
+{
+        /* Clear everything. Note we don't initialize spinlocks
+         * are they aren't supposed to be taken by any of the
+         * NAPI code and this dummy netdev is supposed to be
+         * only ever used for NAPI polls
+         */
+        memset(dev, 0, sizeof(struct net_device));
+
+        /* make sure we BUG if trying to hit standard
+         * register/unregister code path
+         */
+        dev->reg_state = NETREG_DUMMY;
+
+        /* initialize the ref count */
+        atomic_set(&dev->refcnt, 1);
+
+        /* NAPI wants this */
+        INIT_LIST_HEAD(&dev->napi_list);
+
+        /* a dummy interface is started by default */
+        set_bit(__LINK_STATE_PRESENT, &dev->state);
+        set_bit(__LINK_STATE_START, &dev->state);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(init_dummy_netdev);
+
+
+/**
  *      register_netdev - register a network device
  *      @dev: device to register
  *