netdev - Re: [net-next 07/11] e1000e: cleanup Rx checksum offload code

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Message-Id: <20120103.161553.395980097965998086.davem@davemloft.net>
Date:	Tue, 03 Jan 2012 16:15:53 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	bhutchings@...arflare.com
Cc:	jeffrey.t.kirsher@...el.com, bruce.w.allan@...el.com,
	netdev@...r.kernel.org, gospo@...hat.com, sassmann@...hat.com
Subject: Re: [net-next 07/11] e1000e: cleanup Rx checksum offload code

From: Ben Hutchings <bhutchings@...arflare.com>
Date: Tue, 3 Jan 2012 21:00:12 +0000

> On Tue, 2012-01-03 at 15:08 -0500, David Miller wrote:
>> From: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
>> Date: Tue,  3 Jan 2012 11:19:12 -0800
>> 
>> > -		__sum16 sum = (__force __sum16)htons(csum);
>> > +		__sum16 sum = (__force __sum16)htons(le16_to_cpu(csum));
>> 
>> Looks like a NOP.  It's essentially "cpu_to_le16(le16_to_cpu(csum)" as
>> far as I can tell.
> 
> Looks like a swab() to me...

I don't see how it can be.  It's effectively doing a 16-bit swap and
then a 16-bit swap again, which is a NOP.

It's the same as "(__force __sum16) csum" and I bet if the code above
works, then this expression I'm suggesting will work too.
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