David Hawkins wrote:
> When you are dealing with a driver, register accesses need to be
> in a specific format. The MPC8349EA has some of its registers
> in big-endian format, and others in little-endian format.
> Regardless of the mode you operate your processor, you will
> *have* to use the correct byte-swap functions.
That's why we use cpu_to_be32() to write to big-endian registers. On a
big-endian processor, this macro doesn't modify the parameter. So,
*p = be32_to_cpu(12);
will be compiled to
*p = 12;
On a little-endian process, the macro will do a byte-swap.
This macro, and others like it, eliminates the need to have two different
versions of the code.
> DMA would be used to move a block of data, not to manipulate
> a register.
I can see you've never written an audio driver before. The data itself has
endianness, and the register may require the data to appear in one endian or
another. If
--
Timur Tabi
Linux kernel developer at Freescale
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