From e34fac1c2e9ec531c2d63a5e3aa9a6d0ef36a1d3 Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Thu, 5 Apr 2012 14:40:25 +0000 Subject: doc, net: Update ndo_start_xmit return type and values Commit dc1f8bf68b311b1537cb65893430b6796118498a ('netdev: change transmit to limited range type') changed the required return type and 9a1654ba0b50402a6bd03c7b0fe9b0200a5ea7b1 ('net: Optimize hard_start_xmit() return checking') changed the valid numerical return values. Signed-off-by: Ben Hutchings Signed-off-by: David S. Miller --- Documentation/networking/driver.txt | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) (limited to 'Documentation/networking') diff --git a/Documentation/networking/driver.txt b/Documentation/networking/driver.txt index 2128e4169c5b..da59e2884130 100644 --- a/Documentation/networking/driver.txt +++ b/Documentation/networking/driver.txt @@ -2,16 +2,16 @@ Document about softnet driver issues Transmit path guidelines: -1) The ndo_start_xmit method must never return '1' under any - normal circumstances. It is considered a hard error unless +1) The ndo_start_xmit method must not return NETDEV_TX_BUSY under + any normal circumstances. It is considered a hard error unless there is no way your device can tell ahead of time when it's transmit function will become busy. Instead it must maintain the queue properly. For example, for a driver implementing scatter-gather this means: - static int drv_hard_start_xmit(struct sk_buff *skb, - struct net_device *dev) + static netdev_tx_t drv_hard_start_xmit(struct sk_buff *skb, + struct net_device *dev) { struct drv *dp = netdev_priv(dev); @@ -23,7 +23,7 @@ Transmit path guidelines: unlock_tx(dp); printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n", dev->name); - return 1; + return NETDEV_TX_BUSY; } ... queue packet to card ... @@ -35,6 +35,7 @@ Transmit path guidelines: ... unlock_tx(dp); ... + return NETDEV_TX_OK; } And then at the end of your TX reclamation event handling: @@ -61,9 +62,9 @@ Transmit path guidelines: 2) An ndo_start_xmit method must not modify the shared parts of a cloned SKB. -3) Do not forget that once you return 0 from your ndo_start_xmit - method, it is your driver's responsibility to free up the SKB - and in some finite amount of time. +3) Do not forget that once you return NETDEV_TX_OK from your + ndo_start_xmit method, it is your driver's responsibility to free + up the SKB and in some finite amount of time. For example, this means that it is not allowed for your TX mitigation scheme to let TX packets "hang out" in the TX @@ -71,8 +72,9 @@ Transmit path guidelines: This error can deadlock sockets waiting for send buffer room to be freed up. - If you return 1 from the ndo_start_xmit method, you must not keep - any reference to that SKB and you must not attempt to free it up. + If you return NETDEV_TX_BUSY from the ndo_start_xmit method, you + must not keep any reference to that SKB and you must not attempt + to free it up. Probing guidelines: -- cgit v1.2.2