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Message-ID: <20070228214839.GA23772@electric-eye.fr.zoreil.com> Date: Wed, 28 Feb 2007 22:48:39 +0100 From: Francois Romieu <romieu@...zoreil.com> To: Philip Craig <philipc@...pgear.com> Cc: Mike Isely <isely@...ox.com>, Jeff Garzik <jeff@...zik.org>, netdev@...r.kernel.org Subject: Re: [PATCH 4/5] r8169: more alignment for the 0x8168 Sorry for the delay, I took some time to check the history of the r8169 alignment issues. Philip Craig <philipc@...pgear.com> : [...] > This only partially helps. Many of the packets are greater than 200 > bytes so copybreak doesn't apply to them. Yes. > Can we assume anything about the alignment of skb->data? I think it > should be 4 byte aligned, otherwise the whole NET_IP_ALIGN thing > won't work. All the drivers I looked at just reserve NET_IP_ALIGN > without checking the alignment first. > > So can you do something like set align to 0 for RTL_CFG_0 and change > rtl8169_alloc_rx_skb() to: > skb_reserve(skb, align ? (align - 1) & (u32)skb->data : NET_IP_ALIGN); The "So" part assumes that the 0x8169 can DMA at any address. /me ponders... It's easy to debug if it misbehaves now or in 6 months on some obscure system. It's consistent with the preprevious code. Ok, good idea, I like it. [...] > BTW, should the alignment expression be: > (((u32)skb->data + (align - 1)) & ~(align - 1)) - (u32)skb->data I'll see if something can be hacked with a zero or power of two alignment. -- Ueimor - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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