netdev - Re: [PATCH] smsc911x: add fifo byteswap support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090423020925.GA8818@linux-sh.org>
Date:	Thu, 23 Apr 2009 11:09:25 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Steve.Glendinning@...c.com
Cc:	Magnus Damm <magnus.damm@...il.com>, davem@...emloft.net,
	iwamatsu@...auri.org, netdev@...r.kernel.org, Ian.Saturley@...c.com
Subject: Re: [PATCH] smsc911x: add fifo byteswap support

On Wed, Apr 22, 2009 at 04:21:32PM +0100, Steve.Glendinning@...c.com wrote:
> Magnus Damm <magnus.damm@...il.com> wrote on 22/04/2009 15:55:53:
> 
> > From: Magnus Damm <damm@...l.co.jp>
> > 
> > This patch adds fifo byteswap support to the smsc911x driver.
> > 
> > The smsc911x hardware supports both big and little and endian
> > hardware configurations, and the linux smsc911x driver currently
> > detects word order.
> > 
> > For correct operation on big endian platforms lacking swapped
> > byte lanes the following patch is needed. Only fifo data is
> > swapped, register data does not require any swapping. 
> > 
> > Signed-off-by: Magnus Damm <damm@...l.co.jp>
> 
> I guess this is to work around a problem with hardware that's
> already in production?
> 
Good guess ;-)

> The best solution would be to swap the byte lanes in hardware,
> as the device's endian swapping features only affect registers
> (not the FIFOs).  The very latest devices in this family
> (such as the LAN9221) can swap both independently, but this
> driver has to also support older parts.
> 
> Performance will be suboptimal with this software byteswapping,
> so I think we should also add a comment to stress that this is
> a "last resort" workaround for broken hardware.
> 
> Acked-by: Steve Glendinning <steve.glendinning@...c.com>

Performance is not much of a consideration here, it's basically between
this and no ethernet at all. On the plus side, at least not many boards
will need this, I believe it's only 2 generations of microcontroller
evaluation boards that suffer from this particular bit of idiocy on our
side.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html