Re: [PATCH][2.6] IBM PowerPC Virtual Ethernet Driver

[Linus Torvalds]

On Wed, 18 Feb 2004 viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
> > 
> > That can't be right surely ? That would make them utterly useless afaics.
> > I've not seen this happen in practice either with the 2 x86 cpufreq drivers
> > I wrote that both use bitfields extensively.
> 
> It _is_ right and they are utterly useless.  Original rationale was, indeed,
> "describe the layout of hardware registers" but it had gone to hell may years
> ago.  Any assumptions regarding their allocation are non-portable.

Well, to be fair, most compilers still aim to make them useful. 

There's a difference between "the standard doesn't guarantee anything" and 
"the implementation makes no sense". 

(Sadly, a lot of compiler people do seem to look to standards more than
actual users for guides to do things, but at the same time I do believe
that gcc has useful semantics for bitfields and hardware accesses. You
just have to know what the implementation-specific rules are)

		Linus
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