* hi , question function of net_rx(struct net_device *dev)
@ 2014-07-18 9:04 lx
2014-07-18 10:05 ` Denis Kirjanov
0 siblings, 1 reply; 2+ messages in thread
From: lx @ 2014-07-18 9:04 UTC (permalink / raw)
To: kernelnewbies
hi :
the source code of net_rx(struct net_device *dev) is:
http://lxr.oss.org.cn/source/drivers/net/ethernet/cirrus/cs89x0.c#L670
I can't understand codes about malloc buffer.
##########################################
684 /* Malloc up new buffer. */
685 skb = netdev_alloc_skb(dev, length + 2);
686 if (skb == NULL) {
687 dev->stats.rx_dropped++;
688 return;
689 }
690 skb_reserve(skb, 2); /* longword align L3 header */
##########################################
How to explain 'length + 2' in line of 685? Why add 2 ?
Thank you.
^ permalink raw reply [flat|nested] 2+ messages in thread* hi , question function of net_rx(struct net_device *dev) 2014-07-18 9:04 hi , question function of net_rx(struct net_device *dev) lx @ 2014-07-18 10:05 ` Denis Kirjanov 0 siblings, 0 replies; 2+ messages in thread From: Denis Kirjanov @ 2014-07-18 10:05 UTC (permalink / raw) To: kernelnewbies On 7/18/14, lx <lxlenovostar@gmail.com> wrote: > hi : > the source code of net_rx(struct net_device *dev) is: > http://lxr.oss.org.cn/source/drivers/net/ethernet/cirrus/cs89x0.c#L670 > > I can't understand codes about malloc buffer. > ########################################## > 684 /* Malloc up new buffer. */ > 685 skb = netdev_alloc_skb(dev, length + 2); > 686 if (skb == NULL) { > 687 dev->stats.rx_dropped++; > 688 return; > 689 } > 690 skb_reserve(skb, 2); /* longword align L3 header */ > ########################################## > > How to explain 'length + 2' in line of 685? Why add 2 ? That's why it's explained on the line 690. http://lwn.net/Articles/89597/ > Thank you. > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies at kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- Regards, Denis ^ permalink raw reply [flat|nested] 2+ messages in thread
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