linux-kernel - Re: [PATCH v4 1/4] bitfield: Drop underscores from macro parameters

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Message-ID: <CAMuHMdXCoqZmSqRAfujib=2fk0Ob1FiPYWBj8vMXfuXNoKhfVg@mail.gmail.com>
Date: Mon, 20 Oct 2025 14:13:26 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Yury Norov <yury.norov@...il.com>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
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Subject: Re: [PATCH v4 1/4] bitfield: Drop underscores from macro parameters

Hi Yury,

On Fri, 17 Oct 2025 at 18:37, Yury Norov <yury.norov@...il.com> wrote:
> On Fri, Oct 17, 2025 at 12:54:09PM +0200, Geert Uytterhoeven wrote:
> > There is no need to prefix macro parameters with underscores.
> > Remove the underscores.
> >
> > Suggested-by: David Laight <david.laight.linux@...il.com>
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > ---
> > v4:
> >   - Update recently introduced FIELD_MODIFY() macro,

> > --- a/include/linux/bitfield.h
> > +++ b/include/linux/bitfield.h
> > @@ -60,68 +60,68 @@
> >
> >  #define __bf_cast_unsigned(type, x)  ((__unsigned_scalar_typeof(type))(x))
> >
> > -#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)                    \
> > +#define __BF_FIELD_CHECK(mask, reg, val, pfx)                                \
> >       ({                                                              \
> > -             BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),          \
> > -                              _pfx "mask is not constant");          \
> > -             BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero");    \
> > -             BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?           \
> > -                              ~((_mask) >> __bf_shf(_mask)) &        \
> > -                                     (0 + (_val)) : 0,               \
> > -                              _pfx "value too large for the field"); \
> > -             BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \
> > -                              __bf_cast_unsigned(_reg, ~0ull),       \
> > -                              _pfx "type of reg too small for mask"); \
> > -             __BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +                 \
> > -                                           (1ULL << __bf_shf(_mask))); \
> > +             BUILD_BUG_ON_MSG(!__builtin_constant_p(mask),           \
> > +                              pfx "mask is not constant");           \
> > +             BUILD_BUG_ON_MSG((mask) == 0, pfx "mask is zero");      \
> > +             BUILD_BUG_ON_MSG(__builtin_constant_p(val) ?            \
> > +                              ~((mask) >> __bf_shf(mask)) &  \
> > +                                     (0 + (val)) : 0,                \
> > +                              pfx "value too large for the field"); \
> > +             BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) >       \
> > +                              __bf_cast_unsigned(reg, ~0ull),        \
> > +                              pfx "type of reg too small for mask"); \
> > +             __BUILD_BUG_ON_NOT_POWER_OF_2((mask) +                  \
> > +                                           (1ULL << __bf_shf(mask))); \
> >       })
>
> I agree that underscored parameters are excessive. But fixing them has
> a side effect of wiping the history, which is a bad thing.
>
> I would prefer to save a history over following a rule that seemingly
> is not written down. Let's keep this untouched for now, and if there
> will be a need to move the code, we can drop underscores as well.

Fair enough.
So I assume you are fine with not having underscored parameters in
new code, like in [PATCH v4 2/4]?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds