IO, ANSI vs GCC structs

[Paul Mackerras]

Kent Borg writes:

> How important is it to the kernel coding style that hardware be
> accessed through a structure?  Is it acceptable to do:
>
>   #define MYHW  (MY_MBAR+42)
>
>   ...
>
>   out_be32(MYHW, 0xco1df00d);

Hmmm.  You should be using a value returned from ioremap() (or
equivalent) rather than a hard-coded constant.  Yes I know that people
set up 1-1 mappings with io_block_mapping and then do out_be32 to
hard-coded constant addresses but that is deprecated.

My preference is to define the offsets for individual registers as
constants rather than using a structure.

Paul.

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