Re: [PATCH 08/22] bitops: introduce MANY_BITS() macro

[Max Filippov]

Hi Yury,

On Tue, May 10, 2022 at 8:48 AM Yury Norov <yury.norov@xxxxxxxxx> wrote:
> arch/xtensa/kernel/traps.c and include/linux/log2.h define very similar
> functions with different behaviour. XTENSA defines IS_POW2(), and
> log2.h defines is_power_of_2(). The difference is that IS_POW2()
> considers 0 as power of 2, while is_power_of_2() - does not.

IS_POW2 is constructed this way because we know that there is at least
one non-zero bit in the value that it tests.

> This discrepancy may confuse reader. From mathematical point of view,
> 0 is not a power of 2.

If it would reduce the confusion we can add a check that the value is
non-zero in the IS_POW2 macro.

I'd really like to not introduce the local macro and just use something
standard, but I can't use is_power_of_2 in a preprocessor condition,
can I?

-- 
Thanks.
-- Max