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Date: Wed, 01 Feb 2006 12:35:33 -0800
From: David Hawkins <dwh@ovro.caltech.edu>
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To: "Jenkins, Clive" <Clive.Jenkins@xerox.com>
Subject: Re: Yosemite/440EP why are readl()/ioread32() setup to
	readlittle-endian?
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> I said this without looking up the example you cited.
> I agree now, the example is incorrect; and yes, file a bug
> report at oreilly!

Ok, I will.

> I think, from memory, that elsewhere in the book Rubini does
> say that readl()... are for the PCI bus, but cross-arch issues
> are only addressed in certain sections.

I didn't find anything that specifically mentioned their
use was for the PCI bus only. The endianness swapping
features of the pci_config_xxx functions are clearly
stated, but not the readl/writel. And of course the
example I refer to clearly uses those functions on the
PCI bus incorrectly.

But its still a great book.

> I always find out exactly what these macros do on the arch
> I am using, then I know where I stand. I find LXR (Google it if
> you don't know it) good for browsing the source of vanilla
> kernels. After finding out how and where it is done, I then
> double check the relevant files of the actual kernel I am using.
> 
> ppc implementations of readl, writel, cpu_to_le32 use the byte-
> reversed load/store word instructions.

Ahh, very good advice. I think I read about LXR in one of
Freescale's app notes on porting Linux. I'll go take a look
on Google.

Thanks
Dave