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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42f7d331092sm33581359f8f.30.2025.12.09.10.54.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Dec 2025 10:54:53 -0800 (PST) Date: Tue, 9 Dec 2025 18:54:52 +0000 From: David Laight To: Andy Shevchenko Cc: Yury Norov , Rasmus Villemoes , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Geert Uytterhoeven , Alexandre Belloni , Jonathan Cameron , Crt Mori , Richard Genoud , Luo Jie , Peter Zijlstra , Jakub Kicinski , netdev@vger.kernel.org, "David S . Miller" , Simon Horman , Mika Westerberg , Andreas Noever , Yehezkel Bernat , Nicolas Frattaroli Subject: Re: [PATCH 3/9] bitmap: Use FIELD_PREP() in expansion of FIELD_PREP_WM16() Message-ID: <20251209185452.707f4dbe@pumpkin> In-Reply-To: References: <20251209100313.2867-1-david.laight.linux@gmail.com> <20251209100313.2867-4-david.laight.linux@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 9 Dec 2025 17:46:21 +0200 Andy Shevchenko wrote: > On Tue, Dec 09, 2025 at 10:03:07AM +0000, david.laight.linux@gmail.com wrote: > > > 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() and add an extra check for > > the mask being at most 16 bits. > > ... > > > +#define FIELD_PREP_WM16(mask, val) \ > > +({ \ > > + __auto_type _mask = mask; \ > > + u32 _val = FIELD_PREP(_mask, val); \ > > > + BUILD_BUG_ON_MSG(_mask > 0xffffu, \ > > + "FIELD_PREP_WM16: mask too large"); \ > > Can it be static_assert() instead? No, they have to be 'integer constant expressions' not just 'compile time constants'. Pretty useless for anything non-trivial. David > > > + _val | (_mask << 16); \ > > +}) >