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natsemi: Update locking documentation 

The documentation regarding synchronisation at the head of the natsemi
driver was badly bitrotted so replace it with a general statement about
the techniques used which is less likely to bitrot.

Also remove the note saying these chips are uncommon - it makes little
difference but they were used in a number of laptops and at least one mass
market PCI ethernet card.

Signed-off-by: Mark Brown <broonie@sirena.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Mark Brown 2008-01-27 13:58:11 +00:00 committed by David S. Miller
parent 35b5f6b1a8
commit 6344f0521a
1 changed files with 2 additions and 16 deletions
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18
drivers/net/natsemi.c
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@ -203,22 +203,8 @@ skbuff at an offset of "+2", 16-byte aligning the IP header.
IIId. Synchronization
Most operations are synchronized on the np->lock irq spinlock, except the
performance critical codepaths:
The rx process only runs in the interrupt handler. Access from outside
the interrupt handler is only permitted after disable_irq().
The rx process usually runs under the netif_tx_lock. If np->intr_tx_reap
is set, then access is permitted under spin_lock_irq(&np->lock).
Thus configuration functions that want to access everything must call
disable_irq(dev->irq);
netif_tx_lock_bh(dev);
spin_lock_irq(&np->lock);
IV. Notes
NatSemi PCI network controllers are very uncommon.
recieve and transmit paths which are synchronised using a combination of
hardware descriptor ownership, disabling interrupts and NAPI poll scheduling.
IVb. References