Messages in this thread |  | | Date | Tue, 9 Dec 2025 09:56:26 +0000 | | From | David Laight <> | | Subject | Re: [PATCH 3/9] bitmap: Use FIELD_PREP() in expansion of FIELD_PREP_WM16() |
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On Mon, 8 Dec 2025 19:54:37 -0500 Yury Norov <yury.norov@gmail.com> wrote:
> + Nicolas Frattaroli <nicolas.frattaroli@collabora.com> > > It's always good to CC an author of the original implementation, > isn't? > > On Mon, Dec 08, 2025 at 10:42:44PM +0000, david.laight.linux@gmail.com wrote: > > From: David Laight <david.laight.linux@gmail.com> > > > > Instead of directly expanding __BF_FIELD_CHECK() (which really ought > > not be used outside bitfield) and open-coding the generation of the > > masked value, just call FIELD_PREP() > > That's fair. > > > and add an extra check for > > the mask being at most 16 bits. > > Maybe it's time to introduce FIELD_PREP16()? > > > Signed-off-by: David Laight <david.laight.linux@gmail.com> > > --- > > include/linux/hw_bitfield.h | 17 ++++++++--------- > > 1 file changed, 8 insertions(+), 9 deletions(-) > > > > diff --git a/include/linux/hw_bitfield.h b/include/linux/hw_bitfield.h > > index df202e167ce4..d7f21b60449b 100644 > > --- a/include/linux/hw_bitfield.h > > +++ b/include/linux/hw_bitfield.h > > @@ -23,15 +23,14 @@ > > * register, a bit in the lower half is only updated if the corresponding bit > > * in the upper half is high. > > */ > > -#define FIELD_PREP_WM16(_mask, _val) \ > > - ({ \ > > - typeof(_val) __val = _val; \ > > - typeof(_mask) __mask = _mask; \ > > - __BF_FIELD_CHECK(__mask, ((u16)0U), __val, \ > > - "HWORD_UPDATE: "); \ > > - (((typeof(__mask))(__val) << __bf_shf(__mask)) & (__mask)) | \ > > - ((__mask) << 16); \ > > - }) > > +#define FIELD_PREP_WM16(mask, val) \ > > +({ \ > > + __auto_type _mask = mask; \ > > Is __auto_type any better than typeof()?
Generally yes. Mainly because you only get one expansion of the #define parameter.
> > > + u32 _val = FIELD_PREP(_mask, val); \ > > + BUILD_BUG_ON_MSG(_mask > 0xffffu, \ > > + "FIELD_PREP_WM16: mask too large"); \ > > Not necessary to split this line. > > > + _val | (_mask << 16); \ > > +}) > > Can you share bloat-o-meter and code generation examples?
The generated code is going to be pretty much unchanged. The changes only really affect the compile-time checks.
> > For the next version please try to keep as much history > untouched as possible.
I'm going to resend the same patches with the full cc list for now.
David
> > Thanks, > Yury > > > > > /** > > * FIELD_PREP_WM16_CONST() - prepare a constant bitfield element with a mask in > > -- > > 2.39.5
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