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Diffstat (limited to 'Documentation/networking/netdevices.txt')
| -rw-r--r-- | Documentation/networking/netdevices.txt | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/Documentation/networking/netdevices.txt b/Documentation/networking/netdevices.txt new file mode 100644 index 000000000000..1509f3aff968 --- /dev/null +++ b/Documentation/networking/netdevices.txt @@ -0,0 +1,75 @@ + +Network Devices, the Kernel, and You! + + +Introduction +============ +The following is a random collection of documentation regarding +network devices. + +struct net_device allocation rules +================================== +Network device structures need to persist even after module is unloaded and +must be allocated with kmalloc. If device has registered successfully, +it will be freed on last use by free_netdev. This is required to handle the +pathologic case cleanly (example: rmmod mydriver </sys/class/net/myeth/mtu ) + +There are routines in net_init.c to handle the common cases of +alloc_etherdev, alloc_netdev. These reserve extra space for driver +private data which gets freed when the network device is freed. If +separately allocated data is attached to the network device +(dev->priv) then it is up to the module exit handler to free that. + + +struct net_device synchronization rules +======================================= +dev->open: + Synchronization: rtnl_lock() semaphore. + Context: process + +dev->stop: + Synchronization: rtnl_lock() semaphore. + Context: process + Note1: netif_running() is guaranteed false + Note2: dev->poll() is guaranteed to be stopped + +dev->do_ioctl: + Synchronization: rtnl_lock() semaphore. + Context: process + +dev->get_stats: + Synchronization: dev_base_lock rwlock. + Context: nominally process, but don't sleep inside an rwlock + +dev->hard_start_xmit: + Synchronization: dev->xmit_lock spinlock. + When the driver sets NETIF_F_LLTX in dev->features this will be + called without holding xmit_lock. In this case the driver + has to lock by itself when needed. It is recommended to use a try lock + for this and return -1 when the spin lock fails. + The locking there should also properly protect against + set_multicast_list + Context: BHs disabled + Notes: netif_queue_stopped() is guaranteed false + Return codes: + o NETDEV_TX_OK everything ok. + o NETDEV_TX_BUSY Cannot transmit packet, try later + Usually a bug, means queue start/stop flow control is broken in + the driver. Note: the driver must NOT put the skb in its DMA ring. + o NETDEV_TX_LOCKED Locking failed, please retry quickly. + Only valid when NETIF_F_LLTX is set. + +dev->tx_timeout: + Synchronization: dev->xmit_lock spinlock. + Context: BHs disabled + Notes: netif_queue_stopped() is guaranteed true + +dev->set_multicast_list: + Synchronization: dev->xmit_lock spinlock. + Context: BHs disabled + +dev->poll: + Synchronization: __LINK_STATE_RX_SCHED bit in dev->state. See + dev_close code and comments in net/core/dev.c for more info. + Context: softirq + |