From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Sat, 16 Apr 2005 15:20:36 -0700
Subject: Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
---
 Documentation/networking/netdevices.txt | 75 +++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 Documentation/networking/netdevices.txt

(limited to 'Documentation/networking/netdevices.txt')

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
+
-- 
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