[U-Boot] [PATCH v3 02/10] armv7: add miscellaneous utility macros

Wolfgang Denk
2011-05-16T15:52:37Z

Dear Simon Glass,

In message <BANLkTin6o4OEp7aBfCsxpt=z5oZToxVE2g@mail.gmail.com> you wrote:
>
> I believe the problem here is the read/modify/write behaviour which is not
> well-defined in C. One ends up using volatile to ensure the right behaviour,
> and then this doesn't necessarily work either. Where one write must happen

volatile does not help anything here. You MUST always make sure to
use proper I/O accessors. Even in ARM code this has become mandatory
by now, even if older ARM cores and compilers have been forgiving
enough for a long time.

> Perhaps in newer compilers bitfield semantics have been improved?

Bitfields have always been a mess, and should be avoided like hell.

Best regards,

Wolfgang Denk

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