From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Ira Snyder <iws@ovro.caltech.edu>
Cc: PowerPC dev list <linuxppc-dev@ozlabs.org>
Subject: Re: PCI reading without endian conversion
Date: Sat, 21 Feb 2009 15:33:17 +1100 [thread overview]
Message-ID: <1235190797.8805.202.camel@pasglop> (raw)
In-Reply-To: <20090220235054.GA27349@ovro.caltech.edu>
> > 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().
Beware that __raw_* forms also don't have memory barriers.
In general, you know what byte order your device uses (which is often
little endian) and you use the appropriate ioread32{be}. Now, for
userspace, you simply need to mimmic those accessors.
Ben.
next prev parent reply other threads:[~2009-02-21 4:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-20 18:57 PCI reading without endian conversion Matt Sealey
2009-02-20 19:11 ` Ira Snyder
2009-02-20 20:05 ` Matt Sealey
2009-02-20 21:07 ` Ira Snyder
2009-02-20 21:56 ` Matt Sealey
2009-02-20 23:50 ` Ira Snyder
2009-02-21 4:33 ` Benjamin Herrenschmidt [this message]
2009-02-23 10:37 ` Geert Uytterhoeven
2009-02-20 22:37 ` Benjamin Herrenschmidt
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