PCI reading without endian conversion

[Geert Uytterhoeven]

On Fri, 20 Feb 2009, Ira Snyder wrote:
> On Fri, Feb 20, 2009 at 03:56:39PM -0600, Matt Sealey wrote:
> > Am I correct in saying that cpu_to_le32 and le32_to_cpu are the
> > functions/macros I need to use to do byte swapping to make everything
> > go little endian (and back again when I read them back in the kernel)?
> > 
> > Or is there some cleverer way already implemented in the kernel?
> 
> I would say that the __raw_readl() reads in cpu order. If you wanted to
> convert that to le32, you'd use cpu_to_le32().

Well...

__raw_readl() does read in cpu order. But since you're reading from the PCI
bus, which is little endian, you actually read a little endian value. So you
should use le32_to_cpu() to convert it to a native value.

(yes, at the lowest level, cpu_to_le32() and le32_to_cpu() do the same thing
 on PPC: byte swapping 32-bit data).

With kind regards,

Geert Uytterhoeven
Software Architect

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