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Mon, 07 Jul 2025 09:31:24 -0700 (PDT) Date: Mon, 7 Jul 2025 12:31:22 -0400 From: Yury Norov To: Ben Horgan Cc: catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux@rasmusvillemoes.dk, linux-kernel@vger.kernel.org, james.morse@arm.com Subject: Re: [PATCH 2/2] bitfield: Ensure the return value of type##_replace_bits() is checked Message-ID: References: <20250703135729.1807517-1-ben.horgan@arm.com> <20250703135729.1807517-3-ben.horgan@arm.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250703135729.1807517-3-ben.horgan@arm.com> Hi Ben, On Thu, Jul 03, 2025 at 02:57:29PM +0100, Ben Horgan wrote: > As type##_replace_bits() has no side effects it is only useful if its > return value is checked. Add __must_check to enforce this usage. To have > the bits replaced in-place typep##_replace_bits() can be used instead. > > Signed-off-by: Ben Horgan > --- > include/linux/bitfield.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h > index 6d9a53db54b6..39333b80d22b 100644 > --- a/include/linux/bitfield.h > +++ b/include/linux/bitfield.h > @@ -195,8 +195,8 @@ static __always_inline __##type type##_encode_bits(base v, base field) \ > __field_overflow(); \ > return to((v & field_mask(field)) * field_multiplier(field)); \ > } \ > -static __always_inline __##type type##_replace_bits(__##type old, \ > - base val, base field) \ > +static __always_inline __##type __must_check type##_replace_bits(__##type old, \ > + base val, base field) \ > { \ > return (old & ~to(field)) | type##_encode_bits(val, field); \ > } \ So, would it make sense to mark _encode_bits() and _get_bits() as __must_check as well? At least from the point of unification, it would. How would we move this - with my bitmap-for next or with arm branch? Thanks, Yury