From: Christoph Hellwig > Sent: 22 February 2022 16:51 > > On Tue, Feb 22, 2022 at 08:45:53AM -0800, Joe Perches wrote: > > On Tue, 2022-02-22 at 08:31 -0800, Keith Busch wrote: > > > Recent data integrity field enhancements allow 48-bit reference tags. > > > Introduce a helper macro since this will be a repeated operation. > > [] > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > [] > > > @@ -63,6 +63,12 @@ > > > } \ > > > ) > > > > > > +/** > > > + * lower_48_bits - return bits 0-47 of a number > > > + * @n: the number we're accessing > > > + */ > > > +#define lower_48_bits(n) ((u64)((n) & 0xffffffffffffull)) > > > > why not make this a static inline function? > > Agreed. > > > And visually, it's difficult to quickly count a repeated character to 12. > > > > Perhaps: > > > > static inline u64 lower_48_bits(u64 val) > > { > > return val & GENMASK_ULL(47, 0); > > } > > For anyone who has a minimum knowledge of C and hardware your version > is an obsfucated clusterfuck, while the version Keith wrote is trivial > to read. I'd use the explicit: val & ((1ull << 48) - 1) I think it is even fewer characters. David. - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)