Subject: Re: [NET] IOC3: Switch hw checksumming to ethtool configurable.

From: Jeff Garzik <[email-masked]>
Date: Mon, 30 Jul 2007 16:06:54 -0400

Ralf Baechle wrote:
> Signed-off-by: Ralf Baechle <[email-masked]>

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