Yosemite/440EP why are readl()/ioread32() setup to read little-endian?
David Hawkins
dwh at ovro.caltech.edu
Sat Jan 28 10:29:14 EST 2006
Hey Stefan,
>>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?
I just checked the Oreilly web site for errata's and this is not
listed. If you agree that the example is incorrect, then I'll
submit an errata.
Dave
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