lkml.org 
[lkml]   [2022]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 08/22] bitops: introduce MANY_BITS() macro
On Tue, May 10, 2022 at 12:16 PM Yury Norov <yury.norov@gmail.com> wrote:
>
> Hi Max,
>
> On Tue, May 10, 2022 at 10:57:25AM -0700, Max Filippov wrote:
> > Hi Yury,
> >
> > On Tue, May 10, 2022 at 8:48 AM Yury Norov <yury.norov@gmail.com> 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,
>
> This patch introduces a macro MANY_BITS() in include/linux/bitops.h, which
> is a full analogue of IS_POW2(). Would it work for you to switch to
> MANY_BITS()?

It would, I guess. It would also work if is_power_of_2 was a macro.

--
Thanks.
-- Max

\
 
 \ /
  Last update: 2022-05-11 06:56    [W:0.064 / U:0.764 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site