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>
This commit is contained in:
Rusty Russell 2015-04-03 22:17:17 +10:30 committed by David S. Miller
parent 0bd6682722
commit e79d8429aa
1 changed files with 4 additions and 1 deletions

View File

@ -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.
*