[NET]: Make NAPI polling independent of struct net_device objects.

Several devices have multiple independant RX queues per net
device, and some have a single interrupt doorbell for several
queues.

In either case, it's easier to support layouts like that if the
structure representing the poll is independant from the net
device itself.

The signature of the ->poll() call back goes from:

	int foo_poll(struct net_device *dev, int *budget)

to

	int foo_poll(struct napi_struct *napi, int budget)

The caller is returned the number of RX packets processed (or
the number of "NAPI credits" consumed if you want to get
abstract).  The callee no longer messes around bumping
dev->quota, *budget, etc. because that is all handled in the
caller upon return.

The napi_struct is to be embedded in the device driver private data
structures.

Furthermore, it is the driver's responsibility to disable all NAPI
instances in it's ->stop() device close handler.  Since the
napi_struct is privatized into the driver's private data structures,
only the driver knows how to get at all of the napi_struct instances
it may have per-device.

With lots of help and suggestions from Rusty Russell, Roland Dreier,
Michael Chan, Jeff Garzik, and Jamal Hadi Salim.

Bug fixes from Thomas Graf, Roland Dreier, Peter Zijlstra,
Joseph Fannin, Scott Wood, Hans J. Koch, and Michael Chan.

[ Ported to current tree and all drivers converted.  Integrated
  Stephen's follow-on kerneldoc additions, and restored poll_list
  handling to the old style to fix mutual exclusion issues.  -DaveM ]

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/Documentation/networking/netdevices.txt b/Documentation/networking/netdevices.txt
index 37869295fc70..9f7be9b7785e 100644
--- a/Documentation/networking/netdevices.txt
+++ b/Documentation/networking/netdevices.txt
@@ -95,9 +95,13 @@ dev->set_multicast_list:
         Synchronization: netif_tx_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.
+struct napi_struct synchronization rules
+========================================
+napi->poll:
+        Synchronization: NAPI_STATE_SCHED bit in napi->state.  Device
+                driver's dev->close method will invoke napi_disable() on
+                all NAPI instances which will do a sleeping poll on the
+                NAPI_STATE_SCHED napi->state bit, waiting for all pending
+                NAPI activity to cease.
         Context: softirq
                  will be called with interrupts disabled by netconsole.
-