From: Stephen Hemminger <shemminger@linux-foundation.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Johannes Berg <johannes@sipsolutions.net>,
dsd@gentoo.org, davem@davemloft.net, netdev@vger.kernel.org,
linux-wireless@vger.kernel.org
Subject: Re: wireless vs. alignment requirements
Date: Sat, 24 Nov 2007 12:11:08 -0800 [thread overview]
Message-ID: <4748855C.5090103@linux-foundation.org> (raw)
In-Reply-To: <20071124141319.GA27819@gondor.apana.org.au>
Herbert Xu wrote:
> On Sat, Nov 24, 2007 at 02:49:36PM +0100, Johannes Berg wrote:
>
>> Right. I just didn't think that would be a valid value for an
>> architecture to set.
>>
>
> OK. Let me clarify this a bit more. We require at least one
> of the following rules to be met:
>
> * the IPv4/IPv6 header is aligned by 8 bytes on reception;
> * or the platform provides unaligned exception handlers.
>
> So if your platform violates both rules then it won't work with
> the IP stack, simple as that. Fortunately I don't think such a
> platform exists currently on Linux.
>
> Cheers,
>
Then what about hardware that can't dma ethernet to non-aligned address.
Sky2 hardware breaks if DMA is not 8 byte aligned. IMHO the IP stack should
handle any alignment, and do the appropriate memove if the CPU requires
alignment.
WARNING: multiple messages have this Message-ID (diff)
From: Stephen Hemminger <shemminger-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Herbert Xu <herbert-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
Cc: Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>,
dsd-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org,
davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: wireless vs. alignment requirements
Date: Sat, 24 Nov 2007 12:11:08 -0800 [thread overview]
Message-ID: <4748855C.5090103@linux-foundation.org> (raw)
In-Reply-To: <20071124141319.GA27819-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
Herbert Xu wrote:
> On Sat, Nov 24, 2007 at 02:49:36PM +0100, Johannes Berg wrote:
>
>> Right. I just didn't think that would be a valid value for an
>> architecture to set.
>>
>
> OK. Let me clarify this a bit more. We require at least one
> of the following rules to be met:
>
> * the IPv4/IPv6 header is aligned by 8 bytes on reception;
> * or the platform provides unaligned exception handlers.
>
> So if your platform violates both rules then it won't work with
> the IP stack, simple as that. Fortunately I don't think such a
> platform exists currently on Linux.
>
> Cheers,
>
Then what about hardware that can't dma ethernet to non-aligned address.
Sky2 hardware breaks if DMA is not 8 byte aligned. IMHO the IP stack should
handle any alignment, and do the appropriate memove if the CPU requires
alignment.
next prev parent reply other threads:[~2007-11-24 20:13 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-23 0:09 [PATCH] add compare_ether_addr_unaligned Daniel Drake
2007-11-23 4:11 ` Stephen Hemminger
2007-11-23 13:26 ` Herbert Xu
2007-11-26 10:39 ` Herbert Xu
2007-11-23 20:33 ` wireless vs. alignment requirements Johannes Berg
2007-11-24 6:15 ` Herbert Xu
2007-11-24 6:15 ` Herbert Xu
2007-11-24 8:33 ` Johannes Berg
2007-11-24 13:32 ` Herbert Xu
2007-11-24 13:49 ` Johannes Berg
2007-11-24 13:49 ` Johannes Berg
2007-11-24 13:51 ` David Miller
2007-11-24 14:13 ` Herbert Xu
2007-11-24 20:11 ` Stephen Hemminger [this message]
2007-11-24 20:11 ` Stephen Hemminger
2007-11-24 21:33 ` Johannes Berg
2007-11-24 21:33 ` Johannes Berg
2007-11-25 1:08 ` Herbert Xu
2007-11-25 1:08 ` Herbert Xu
2007-11-25 21:21 ` Stephen Hemminger
2007-11-25 21:21 ` Stephen Hemminger
2007-11-26 1:38 ` Herbert Xu
2007-11-26 1:38 ` Herbert Xu
2007-11-27 17:16 ` H. Peter Anvin
2007-11-27 17:16 ` H. Peter Anvin
2007-11-27 17:16 ` H. Peter Anvin
2007-11-27 18:39 ` Stephen Hemminger
2007-11-27 18:39 ` Stephen Hemminger
2007-11-28 2:42 ` H. Peter Anvin
2007-11-28 2:42 ` H. Peter Anvin
2007-11-29 13:11 ` Herbert Xu
2007-11-29 13:11 ` Herbert Xu
2007-11-29 17:50 ` H. Peter Anvin
2007-11-30 0:26 ` Herbert Xu
2007-11-30 0:28 ` H. Peter Anvin
2007-11-30 0:28 ` H. Peter Anvin
2007-11-30 0:34 ` Herbert Xu
2007-11-30 0:34 ` Herbert Xu
2007-11-30 0:41 ` H. Peter Anvin
2007-11-30 0:41 ` H. Peter Anvin
2007-11-24 21:13 ` Johannes Berg
2007-11-24 21:13 ` Johannes Berg
2007-11-25 1:44 ` Herbert Xu
2007-11-25 1:44 ` Herbert Xu
2007-11-25 11:00 ` Johannes Berg
2007-11-25 11:00 ` Johannes Berg
2007-11-25 11:22 ` Herbert Xu
2007-11-25 11:22 ` Herbert Xu
2007-11-25 13:54 ` Johannes Berg
2007-11-25 14:01 ` Herbert Xu
2007-11-25 14:01 ` Herbert Xu
2007-11-25 17:04 ` Johannes Berg
2007-11-26 1:36 ` Herbert Xu
2007-11-26 1:36 ` Herbert Xu
2007-11-24 13:11 ` Ulrich Kunitz
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