From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Perches <joe@perches.com>
Subject: Re: [PATCH net-next] net: macb: replace literal constant with
 NET_IP_ALIGN
Date: Wed, 01 Jul 2015 16:00:56 -0700
Message-ID: <1435791656.12101.128.camel@perches.com>
References: <5592D105.7080006@certsign.ro>
	 <1435748191.4110.127.camel@edumazet-glaptop2.roam.corp.google.com>
	 <1435770389.12101.110.camel@perches.com>
	 <1435788837.8526.3.camel@edumazet-glaptop2.roam.corp.google.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7bit
Cc: Nicolae Rosia <nicolae.rosia@certsign.ro>, netdev@vger.kernel.org,
	'Nicolas Ferre <nicolas.ferre@atmel.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from smtprelay0118.hostedemail.com ([216.40.44.118]:34962 "EHLO
	smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL)
	by vger.kernel.org with ESMTP id S1750793AbbGAXA7 (ORCPT
	<rfc822;netdev@vger.kernel.org>); Wed, 1 Jul 2015 19:00:59 -0400
In-Reply-To: <1435788837.8526.3.camel@edumazet-glaptop2.roam.corp.google.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Thu, 2015-07-02 at 00:13 +0200, Eric Dumazet wrote:
> On Wed, 2015-07-01 at 10:06 -0700, Joe Perches wrote:
> > On Wed, 2015-07-01 at 12:56 +0200, Eric Dumazet wrote:
> > > On Tue, 2015-06-30 at 20:25 +0300, Nicolae Rosia wrote:
> > > > diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> > []
> > > > @@ -2554,9 +2554,9 @@ static void at91ether_rx(struct net_device *dev)
> > > >  	while (lp->rx_ring[lp->rx_tail].addr & MACB_BIT(RX_USED)) {
> > > >  		p_recv = lp->rx_buffers + lp->rx_tail * AT91ETHER_MAX_RBUFF_SZ;
> > > >  		pktlen = MACB_BF(RX_FRMLEN, lp->rx_ring[lp->rx_tail].ctrl);
> > > > -		skb = netdev_alloc_skb(dev, pktlen + 2);
> > > > +		skb = netdev_alloc_skb(dev, pktlen + NET_IP_ALIGN);
> > > >  		if (skb) {
> > > > -			skb_reserve(skb, 2);
> > > > +			skb_reserve(skb, NET_IP_ALIGN);
> > > >  			memcpy(skb_put(skb, pktlen), p_recv, pktlen);
> > > >  
> > > >  			skb->protocol = eth_type_trans(skb, dev);
> > > 
> > > Then please use netdev_alloc_skb_ip_align(), so that you get rid of
> > > skb_reserve()
> > 
> > It seems there are ~50 of these in the kernel tree
> > that could be converted.
> > 
> 
> Make sure the 2 is really NET_IP_ALIGN
> 
> Some hardwares need 2, even if NET_IP_ALIGN is 0 (on x86 arches for
> example)
> 
> I would rather not touch this without testing the change on real
> hardware.

Nor I really.

Most all of those are in fairly old hardware drivers.

I just wanted to point out that more exist.