Yosemite/440EP why are readl()/ioread32() setup to readlittle-endian?

[Jenkins, Clive]

> >>readl() and ioread32() read the registers in little-endian format!
> >
> > Correct. That's how it is implemented on all platforms. Think for
> > example of an pci device driver. Using these IO functions, the
> > driver will become platform independent, running without
> > modifications on little- and big-endian machines.
>
> I just stumbled across the section in Rubini 3rd Ed that mislead
> me into believing that the readl()/writel() were machine endianness
> dependent, i.e., LE on x86, BE on PPC.

> p453 of his book has a PCI DMA example, where he uses the
> cpu_to_le32() macros inside calls writel().

> However, since these functions are internally implemented to
> perform LE operations, this example appears to be incorrect.

> Would you agree?

No, I think it is correct.

On most architectures readl() and writel() assume you are
accessing MMIO on the PCI bus, which is little-endian.
So these macros convert between the endian-ness of the CPU
and the endian-ness of the PCI bus.

Clive