linux-kernel - Re: [PATCH v10 1/4] bitops: Introduce the for_each_set

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Date:   Sat, 3 Oct 2020 20:38:14 +0530
From:   Syed Nayyar Waris <syednwaris@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 1/4] bitops: Introduce the for_each_set_clump macro

On Sat, Oct 3, 2020 at 6:32 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sat, Oct 3, 2020 at 3:56 PM William Breathitt Gray
> <vilhelm.gray@...il.com> wrote:
> > On Sat, Oct 03, 2020 at 03:45:04PM +0300, Andy Shevchenko wrote:
> > > On Sat, Oct 3, 2020 at 2:37 PM Syed Nayyar Waris <syednwaris@...il.com> wrote:
> > > > On Sat, Oct 3, 2020 at 2:14 PM Andy Shevchenko
> > > > <andy.shevchenko@...il.com> wrote:
> > > > > On Sat, Oct 3, 2020 at 2:51 AM Syed Nayyar Waris <syednwaris@...il.com> wrote:
>
> ...
>
> > > > > > +               map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
> > > > > > +               map[index] |= value << offset;
> > >
> > > Side note: I would prefer + 0 here and there, but it's up to you.

Andy what do you mean by the above statement, can you please clarify?
Can you please elaborate on the above statement.

Thanks

> > >
> > > > > > +               map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
> > > > > > +               map[index + 1] |= (value >> space);
> > >
> > > By the way, what about this in the case of start=0, nbits > 64?
> > > space == 64 -> UB.
> > >
> > > (And btw parentheses are redundant here)
> >
> > I think this is the same situation as before: we should document that
> > nbits must be between 1 and BITS_PER_LONG.
>
> At least documented, yes.
>
> --
> With Best Regards,
> Andy Shevchenko