From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
To: Stephen Hemminger
<shemminger-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Herbert Xu
<herbert-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>,
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: Tue, 27 Nov 2007 09:16:07 -0800 [thread overview]
Message-ID: <474C50D7.5010901@zytor.com> (raw)
In-Reply-To: <4748855C.5090103-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Stephen Hemminger wrote:
> 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.
I wrote a patch for the IP stack to realign packets if necessary at one
point. I should dredge it up again and submit it for collective flamage.
-hpa
next prev parent reply other threads:[~2007-11-27 17:16 UTC|newest]
Thread overview: 35+ 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
[not found] ` <1195850001.4149.165.camel-YfaajirXv214zXjbi5bjpg@public.gmane.org>
2007-11-24 6:15 ` Herbert Xu
2007-11-24 8:33 ` Johannes Berg
2007-11-24 13:32 ` Herbert Xu
[not found] ` <20071124133200.GA27531-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
2007-11-24 13:49 ` Johannes Berg
2007-11-24 13:51 ` David Miller
2007-11-24 14:13 ` Herbert Xu
[not found] ` <20071124141319.GA27819-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
2007-11-24 20:11 ` Stephen Hemminger
[not found] ` <4748855C.5090103-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2007-11-24 21:33 ` Johannes Berg
2007-11-25 1:08 ` Herbert Xu
[not found] ` <20071125010814.GD31668-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
2007-11-25 21:21 ` Stephen Hemminger
[not found] ` <4749E768.9040002-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2007-11-26 1:38 ` Herbert Xu
2007-11-27 17:16 ` H. Peter Anvin
2007-11-27 17:16 ` H. Peter Anvin [this message]
[not found] ` <474C50D7.5010901-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2007-11-27 18:39 ` Stephen Hemminger
[not found] ` <20071127103940.314c7844-s08KbqtN0aBORcJjwVk881hTQxXnIo14@public.gmane.org>
2007-11-28 2:42 ` H. Peter Anvin
2007-11-29 13:11 ` Herbert Xu
2007-11-29 17:50 ` H. Peter Anvin
2007-11-30 0:26 ` Herbert Xu
[not found] ` <20071130002621.GI23769-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
2007-11-30 0:28 ` H. Peter Anvin
[not found] ` <474F5932.1030103-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2007-11-30 0:34 ` Herbert Xu
[not found] ` <20071130003426.GJ23769-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
2007-11-30 0:41 ` H. Peter Anvin
2007-11-24 21:13 ` Johannes Berg
[not found] ` <1195938799.4149.197.camel-YfaajirXv214zXjbi5bjpg@public.gmane.org>
2007-11-25 1:44 ` Herbert Xu
[not found] ` <20071125014446.GA32104-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org>
2007-11-25 11:00 ` Johannes Berg
[not found] ` <1195988428.4149.225.camel-YfaajirXv214zXjbi5bjpg@public.gmane.org>
2007-11-25 11:22 ` Herbert Xu
2007-11-25 13:54 ` Johannes Berg
[not found] ` <1195998864.4149.229.camel-YfaajirXv214zXjbi5bjpg@public.gmane.org>
2007-11-25 14:01 ` Herbert Xu
2007-11-25 17:04 ` Johannes Berg
[not found] ` <1196010257.4149.234.camel-YfaajirXv214zXjbi5bjpg@public.gmane.org>
2007-11-26 1:36 ` Herbert Xu
2007-11-24 13:11 ` Ulrich Kunitz
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=474C50D7.5010901@zytor.com \
--to=hpa-ymnouzjc4hwavxtiumwx3w@public.gmane.org \
--cc=davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org \
--cc=dsd-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org \
--cc=herbert-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org \
--cc=johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org \
--cc=linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=shemminger-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).