Re: [tip:x86/mce] x86/bitops: Move BIT_64() for a wider use

[Borislav Petkov]

On Wed, May 23, 2012 at 09:31:17AM -0700, H. Peter Anvin wrote:
> >>
> >> Actually we need a BIT() macro that works both
> >> on 32- and 64-bit. But that won't be that easy:
> >> http://lkml.indiana.edu/hypermail/linux/kernel/1010.1/02335.html
> >>
> >> And it should return UL for shift values < 32 and ULL otherwise.
> > 
> 
> Why do you want that behavior?  That seems bizarre...

I forgot to say "on 32-bit" above. So the sentence should've been:

"And it should return UL for shift values < 32 and ULL otherwise on
32-bit."

How about the following completely untested chunk:

#ifdef CONFIG_64BIT
#define BIT(nr)		(UC_64(1) << (nr))
#else
#define BIT(nr)	\
({ \
	unsigned _shift = (nr);	\
 	((_shift > 32) ? (U64_C(1) << _shift) : (U32_C(1) << _shift)); \
})
#endif

Ok? Too ugly? It still changes the return type of unsigned long to ULL
for shift values >= 32 and probably Linus doesn't want that...

Hmm.

-- 
Regards/Gruss,
    Boris.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/