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Mon, 08 Dec 2025 16:54:38 -0800 (PST) Date: Mon, 8 Dec 2025 19:54:37 -0500 From: Yury Norov To: david.laight.linux@gmail.com Cc: Rasmus Villemoes , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Geert Uytterhoeven , Nicolas Frattaroli Subject: Re: [PATCH 3/9] bitmap: Use FIELD_PREP() in expansion of FIELD_PREP_WM16() Message-ID: References: <20251208224250.536159-1-david.laight.linux@gmail.com> <20251208224250.536159-4-david.laight.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251208224250.536159-4-david.laight.linux@gmail.com> + Nicolas Frattaroli 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 > > 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 > --- > 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()? > + 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? For the next version please try to keep as much history untouched as possible. Thanks, Yury > > /** > * FIELD_PREP_WM16_CONST() - prepare a constant bitfield element with a mask in > -- > 2.39.5