netdev - Re: [PATCH] bgmac: fix unaligned accesses to network headers

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Date:	Sat, 16 Feb 2013 10:36:12 -0800
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Hauke Mehrtens <hauke@...ke-m.de>
Cc:	davem@...emloft.net, zajec5@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] bgmac: fix unaligned accesses to network headers

On Sat, 16 Feb 2013 15:32:34 +0100
Hauke Mehrtens <hauke@...ke-m.de> wrote:

> Without this patch I get many unaligned access warnings per packet,
> this patches fixes them all. This should improve performance ony some
> systems like mips.
> 
> Signed-off-by: Hauke Mehrtens <hauke@...ke-m.de>
> ---
>  drivers/net/ethernet/broadcom/bgmac.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
> index d341090..f9b1bc8 100644
> --- a/drivers/net/ethernet/broadcom/bgmac.c
> +++ b/drivers/net/ethernet/broadcom/bgmac.c
> @@ -301,8 +301,9 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
>  			bgmac_err(bgmac, "Found poisoned packet at slot %d, DMA issue!\n",
>  				  ring->start);
>  		} else {
> -			new_skb = netdev_alloc_skb(bgmac->net_dev, len);
> +			new_skb = netdev_alloc_skb(bgmac->net_dev, len + 2);
>  			if (new_skb) {
> +				skb_reserve(new_skb, 2);
>  				skb_put(new_skb, len);
>  				skb_copy_from_linear_data_offset(skb, BGMAC_RX_FRAME_OFFSET,
>  								 new_skb->data,

NAK. Use netdev_alloc_skb_ip_align instead. 
It is less error prone, and handles case of architectures where unaligned is faster.
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