lkml.org 
[lkml]   [2011]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] asm-generic/io.h: Fix io{read,write}{16,32}be for big endian systems
Date
On Tuesday 18 January 2011 19:11:01 Lars-Peter Clausen wrote:
> Currently io{read,write}{16,32} expand to
> *addr = cpu_to_leXX(cpu_to_beXX(val))
> and
> val = beXX_to_cpu(leXX_to_cpu(*addr))
>
> While it should rather be:
> *addr = cpu_to_be{16,32}(val)
> and
> val = be{16,32}_to_cpu(*addr)
>
> The current implementation works on litte-endian targets(where cpu_to_leXX is a
> noop), but breaks on on big-endian targets, this patch fixes it.
>
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

The existing code looks broken on big-endian indeed, thanks
for the report!

However, you cannot use __raw_readl in general, because that
function knows nothing about the various kinds of I/O accesses
(potentially) handled by readl. Think of architectures where
readl is not a pointer dereference but something else.

The right solution is probably to use swab16/swab32 for the
big-endian functions. This also corrects the iowrite functions
which really should be using cpu_to_be32 instead of be32_to_cpu
(although they are always defined to be the same afaict.

Arnd


\
 
 \ /
  Last update: 2011-01-18 19:47    [W:0.043 / U:1.544 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site