From: Michael Buesch <mb@bu3sch.de>
To: matthieu castet <castet.matthieu@free.fr>
Subject: Re: b43 : unaligned access on mips
Date: Tue, 2 Jun 2009 17:20:38 +0200
Cc: linux-wireless@vger.kernel.org
References: <4A244E19.7090501@free.fr> <4A244F6C.3000509@free.fr>
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On Tuesday 02 June 2009 00:00:12 matthieu castet wrote:
> matthieu castet wrote:
> > Hi,
> > 
> > b43_generate_plcp_hdr generate unaligned access on mips with gcc [1] 
> > from openwrt.
> > 
> > A small testcase [2] show that &plcp->data is access as a 32 bit aligned 
> > variable (see the "lw      $2,0($4)" and "sw      $2,0($4)").
> > I don't know enough mips to know if it is a gcc bug (ignoring the packed 
> > attribute) or something missing in b43 code.
> For example using "plcp->data" instead "*data" produce the correct code.

Uhm, I'm not sure. This code has been in the driver as-is forever and I don't
see any unaligned access issues on mips (I checked a month or so ago).
The plcp data structure is also __attribute__((packed)), so there can't be any
unaligned accesses, as gcc is required to _expect_ unaligned accesses on structures
with packed attribute. So it is required to do byte accesses on architectures where
alignment matters.
So I don't think there's an issue in the code.

-- 
Greetings, Michael.