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authorRusty Russell <rusty@rustcorp.com.au>2015-04-03 22:17:17 +1030
committerDavid S. Miller <davem@davemloft.net>2015-04-03 12:37:36 -0400
commite79d8429aac95a5cbe4c235795c7cd554c91f924 (patch)
tree3989a7a6e5c63fd999a1e329ea80dea0788453b2 /include/linux
parent0bd66827220a7292bfbed54fb547c83363e07405 (diff)
netdevice: document NETDEV_TX_BUSY deprecation.
This paraphrases DaveM (and steals some of his words) explaining why a device shouldn't return NETDEV_TX_BUSY, even though it looks so inviting to driver authors. See http://www.spinics.net/lists/netdev/msg322350.html Inspired-by: David Miller <davem@davemloft.net> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/netdevice.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 846a1f5bc9db..a710d22b174f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -795,7 +795,10 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
* netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb,
* struct net_device *dev);
* Called when a packet needs to be transmitted.
- * Must return NETDEV_TX_OK , NETDEV_TX_BUSY.
+ * Returns NETDEV_TX_OK. Can return NETDEV_TX_BUSY, but you should stop
+ * the queue before that can happen; it's for obsolete devices and weird
+ * corner cases, but the stack really does a non-trivial amount
+ * of useless work if you return NETDEV_TX_BUSY.
* (can also return NETDEV_TX_LOCKED iff NETIF_F_LLTX)
* Required can not be NULL.
*