From: Stephen Hemminger <shemminger@osdl.org>
To: Ben Greear <greearb@candelatech.com>
Cc: Ingo Oeser <ioe-lkml@rameria.de>, Ingo Oeser <netdev@axxeo.de>,
Denis Vlasenko <vda@ilport.com.ua>,
Dave Dillow <dave@thedillows.org>,
netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
linux-kernel@vger.kernel.org, jgarzik@pobox.com
Subject: Re: [RFD][PATCH] typhoon and core sample for folding away VLAN stuff
Date: Wed, 12 Apr 2006 13:23:22 -0700 [thread overview]
Message-ID: <20060412132322.7786111b@localhost.localdomain> (raw)
In-Reply-To: <443D5E9E.80002@candelatech.com>
On Wed, 12 Apr 2006 13:10:06 -0700
Ben Greear <greearb@candelatech.com> wrote:
> What is the reasoning for this change? Is the compiler
> able to optomize the right-hand-side to a constant with your
> change in place?
>
> > - if (veth->h_vlan_proto != __constant_htons(ETH_P_8021Q)) {
> > + if (veth->h_vlan_proto != htons(ETH_P_8021Q)) {
> > return -EINVAL;
> > }
Read the source, the macro handles it.
For i386:
htons maps to __cpu_to_be16
cpu_to_be16 maps to swab16 which is defined in swab.h
# define __swab16(x) \
(__builtin_constant_p((__u16)(x)) ? \
___swab16((x)) : \
__fswab16((x)))
next prev parent reply other threads:[~2006-04-12 20:24 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200604071628.30486.vda@ilport.com.ua>
[not found] ` <200604101716.58463.vda@ilport.com.ua>
[not found] ` <1144682807.12177.22.camel@dillow.idleaire.com>
2006-04-11 7:28 ` [PATCH] deinline a few large functions in vlan code v2 Denis Vlasenko
2006-04-11 8:02 ` David S. Miller
2006-04-11 9:49 ` Ingo Oeser
[not found] ` <200604111502.52302.vda@ilport.com.ua>
2006-04-11 13:17 ` Ingo Oeser
2006-04-12 19:32 ` [RFD][PATCH] typhoon and core sample for folding away VLAN stuff (was: Re: [PATCH] deinline a few large functions in vlan code v2) Ingo Oeser
2006-04-12 20:10 ` [RFD][PATCH] typhoon and core sample for folding away VLAN stuff Ben Greear
2006-04-12 20:23 ` Stephen Hemminger [this message]
2006-04-12 20:51 ` David S. Miller
2006-04-13 1:24 ` Dave Dillow
2006-04-13 8:38 ` Denis Vlasenko
2006-04-13 15:00 ` Dave Dillow
2006-04-11 13:59 ` [PATCH] deinline a few large functions in vlan code v2 Dave Dillow
2006-04-12 8:55 ` Denis Vlasenko
2006-04-12 17:18 ` Dave Dillow
2006-04-13 6:04 ` Denis Vlasenko
2006-04-13 14:59 ` Dave Dillow
2006-04-13 11:32 ` Ingo Oeser
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