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Re: [PATCH 2.6.9-rc2 8/8] S2io: two buffer mode

To: Raghavendra Koushik <raghavendra.koushik@xxxxxxxx>
Subject: Re: [PATCH 2.6.9-rc2 8/8] S2io: two buffer mode
From: Chris Leech <chris.leech@xxxxxxxxx>
Date: Thu, 14 Oct 2004 13:49:02 -0700
Cc: Jeff Garzik <jgarzik@xxxxxxxxx>, ravinandan.arakali@xxxxxxxx, Francois Romieu <romieu@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxx, leonid.grossman@xxxxxxxx, rapuru.sriram@xxxxxxxx
In-reply-to: <200410141833.i9EIXI39018452@xxxxxxxxxxxxxxxxx>
References: <416E9550.4060001@xxxxxxxxx> <200410141833.i9EIXI39018452@xxxxxxxxxxxxxxxxx>
Reply-to: Chris Leech <chris.leech@xxxxxxxxx>
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On Thu, 14 Oct 2004 11:33:13 -0700, Raghavendra Koushik
<raghavendra.koushik@xxxxxxxx> wrote:

> > 1) can this not be done with SKB fragments?
> > 
> To acheve what is required, the H/W still has to split the Rx'ed frame into
> 2 parts. By implementing this through the SKB fragments method, the only
> thing we avoid is usage of ba_0 and ba_1 fields, but note that none of these
> are allocated or freed in fast path. They are all pre-allocated buffers
> (along with the Rx descriptors) and hence won't hit the Rx side performance.
> Also by pulling down the eth_type_trans implementation partially into the
> driver any kind of copy during Rx is also avoided.

This change would pass skbs from the driver without the MAC header? 
What happens in a bridging configuration?  And dev->hard_header_parse
is set to eth_header_parse, which expects skb->mac.ethernet to be
valid, so I think any use of packet sockets will result in a NULL
dereference.

- Chris

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