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Re: I need sk_buff frag_list info.

To: Andi Kleen <ak@xxxxxxx>
Subject: Re: I need sk_buff frag_list info.
From: andrew may <acmay@xxxxxxxxxxxxxxxx>
Date: Fri, 15 Mar 2002 16:47:21 -0800
Cc: Mark Wisner <markwiz@xxxxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <20020316013712.A10179@xxxxxxxxxxxxx>
References: <OF1B1A2F76.97320533-ON85256B7D.00695592@xxxxxxxxxxxxxxx> <20020316013712.A10179@xxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
On Sat, Mar 16, 2002 at 01:37:12AM +0100, Andi Kleen wrote:
> On Fri, Mar 15, 2002 at 02:15:22PM -0500, Mark Wisner wrote:
> > I am working on a change to the IBM 405 Ethernet driver. The Ethernet
> 
> What is an IBM 405? 

An embedded PPC chip, with the ethernet built into the chip.

> Only when you don't want to support TCP. TCP will always reallocate and copy 
> list linked packets currently. 
> frag_list is purely a hack to handle fragmented packets for UDP and RAW.
> 
> Instead you should use the skb data array (skb_shinfo()->frags) and fill
> it with page sized chunks. 
> Documentation on how to use that is unfortunately a bit scarce, you'll need
> to do some RTFS. 

Well I still have not seen any ethernet card do this. Even though it seems
that the hardware would support it. This could be a big help for jumbo frames
with GigE.

So if you suggest to use ->frags should the skb->data be left alone? 
I can see no way off knowing ahead of time wether the ptr's giving to
hardware for a rx will be used for the start of a packet.


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