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Message-ID: <46AE44DE.8000107@garzik.org>
Date: Mon, 30 Jul 2007 16:06:54 -0400
From: Jeff Garzik <jeff@...zik.org>
To: Ralf Baechle <ralf@...ux-mips.org>
CC: netdev@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
"David S. Miller" <davem@...emloft.net>,
Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [NET] IOC3: Switch hw checksumming to ethtool configurable.
Ralf Baechle wrote:
> Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
applied to #upstream (2.6.24)
> I've previously sent out this patch a long time ago. At that time I was
> told NETIF_F_IP_CSUM wouldn't make any sense without NETIF_F_SG. IOC3's
> S/G abilities are very limited; it can do upto three segments of which
> the first one is upto 104 bytes and part of the packet's TX ring entry,
> the second and 3rd ones can be anywhere in the 64-bit PCI address space
> but may not cross a 16kB page boundary. So setting NETIF_F_SG isn't
> really an option unless the IOC3 was going to linearize any packet it
> can't cope with itself.
>
> So the big question, does NETIF_F_IP_CSUM without NETIF_F_SG make sense?
Conventional wisdom has always been that NETIF_F_SG is required if
NETIF_F_*CSUM is present, and vice versa.
I admit I've not verified this in the past year or two.
Jeff
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