From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E0E6F1874 for ; Wed, 19 Oct 2022 10:31:28 +0000 (UTC) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-306-19UG_-sFOqOSys9fWgfDtg-1; Wed, 19 Oct 2022 11:31:19 +0100 X-MC-Unique: 19UG_-sFOqOSys9fWgfDtg-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.42; Wed, 19 Oct 2022 11:31:17 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.042; Wed, 19 Oct 2022 11:31:17 +0100 From: David Laight To: 'Kang Minchul' , Greg Kroah-Hartman , Paulo Miguel Almeida CC: Dan Carpenter , Sidong Yang , "linux-staging@lists.linux.dev" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] staging: pi433: Use div64_u64 instead of do_div Thread-Topic: [PATCH] staging: pi433: Use div64_u64 instead of do_div Thread-Index: AQHY46M8g2A3zaXXyE2gPdBmwjkSwq4Vg27w Date: Wed, 19 Oct 2022 10:31:17 +0000 Message-ID: References: <20221019094015.832398-1-tegongkang@gmail.com> In-Reply-To: <20221019094015.832398-1-tegongkang@gmail.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable From: Kang Minchul > Sent: 19 October 2022 10:40 >=20 > This commit removes warning generated by cocci as follows: >=20 > do_div() does a 64-by-32 division, please consider using div64_u64 instea= d. >=20 > Using div64_u64 instead of do_div can avoid potential truncation. Cocci is lying to you. do_div() exists because a 64 by 32 bit divide is significantly faster than a 64 by 64 divide. This is particularly true on 32bit cpu, but is also true on Intel x86_64 bit cpu. So unless the result might actually be larger than 32 bits (which requires code analysis) then do_div() is correct. =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)