Re: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro

Christoph Hellwig
2022-02-22T16:50:54Z

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.