Re: [PATCH 5/8] bitsperlong.h: introduce SMALL_CONST() macro

Yury Norov
2021-02-02T07:11:20Z

On Mon, Feb 1, 2021 at 5:45 AM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Sat, Jan 30, 2021 at 11:17:16AM -0800, Yury Norov wrote:
> > Many algorithms become simpler if they are passed with relatively small
> > input values. One example is bitmap operations when the whole bitmap fits
> > into one word. To implement such simplifications, linux/bitmap.h declares
> > small_const_nbits() macro.
> >
> > Other subsystems may also benefit from optimizations of this sort, like
> > find_bit API in the following patches. So it looks helpful to generalize
> > the macro and extend it's visibility.
>
> Hmm... Are we really good to allow 0 as a parameter to it? I remember we had
> a thread at some point where Rasmus explained why 0 is excluded.

Now we pass (nbits - 1) instead of nbits, which is ULONG_MAX in case
of nbits == 0

> > --- a/tools/include/asm-generic/bitsperlong.h
> > +++ b/tools/include/asm-generic/bitsperlong.h
>
> Tools part in a separate patch?
>
> --
> With Best Regards,
> Andy Shevchenko
>
>