From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EE0C2C433F5 for ; Tue, 22 Feb 2022 17:21:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:In-Reply-To:References:Message-ID:Date:Subject:CC: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=rS7FOcGHzkW+FD0d4tijJY6g6jr/VheAQ/gag2x5rWE=; b=sMWDmZFJFAn19/WQNIt5FyJgkt fGsO8343JtPiEL1I9LzEVUKrfz5DhGXyYlYz4o6/BPtBDfsYPqqkosOoDXotIb4ZqtMRKk6l2TAAP 9N0G5Yc9XI5ca8FL4rZqqvRD0yvlr/D7feFWKiAF2hkH5zgn3IqrZncQPXo5R7Cj8EpSPPDnlzjIG VIje2N8X9ybWkKNTZCHQUpAD7qLkOI43xAI9pFzmmFPg7JNzs8ceNqaknKdw4vDJaP9e6dbsgy77w /Z0RjYkcuf16eX72pLEaIoybuo2ZRfA5LasLVwqa2pCPeshLm+/Z1X1d0bcqlMCBBppVhBawHgzhV KvfPUIag==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMYrK-00AxHh-Dy; Tue, 22 Feb 2022 17:21:54 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMYfg-00AsMf-BN for linux-nvme@lists.infradead.org; Tue, 22 Feb 2022 17:09:54 +0000 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-210-AoyiLaE1OJah7Pz61gNshw-1; Tue, 22 Feb 2022 17:09:49 +0000 X-MC-Unique: AoyiLaE1OJah7Pz61gNshw-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.28; Tue, 22 Feb 2022 17:09:47 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.028; Tue, 22 Feb 2022 17:09:47 +0000 From: David Laight To: 'Christoph Hellwig' , Joe Perches CC: Keith Busch , "linux-nvme@lists.infradead.org" , "linux-block@vger.kernel.org" , "linux-crypto@vger.kernel.org" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "axboe@kernel.dk" , "martin.petersen@oracle.com" , "colyli@suse.de" , "Bart Van Assche" Subject: RE: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro Thread-Topic: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro Thread-Index: AQHYKAxbyZzL6Kc8n0eksk5bzcXivKyfzIzQ Date: Tue, 22 Feb 2022 17:09:47 +0000 Message-ID: References: <20220222163144.1782447-1-kbusch@kernel.org> <20220222163144.1782447-5-kbusch@kernel.org> <66a0c8210cf9e7dfcc3fa2d247de1eebd5a8acb7.camel@perches.com> <20220222165045.GA14168@lst.de> In-Reply-To: <20220222165045.GA14168@lst.de> 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] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220222_090952_712467_0F180DDD X-CRM114-Status: GOOD ( 15.90 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org From: Christoph Hellwig > Sent: 22 February 2022 16:51 >=20 > On Tue, Feb 22, 2022 at 08:45:53AM -0800, Joe Perches wrote: > > On Tue, 2022-02-22 at 08:31 -0800, Keith Busch wrote: > > > Recent data integrity field enhancements allow 48-bit reference tags. > > > Introduce a helper macro since this will be a repeated operation. > > [] > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > [] > > > @@ -63,6 +63,12 @@ > > > }=09=09=09=09=09\ > > > ) > > > > > > +/** > > > + * lower_48_bits - return bits 0-47 of a number > > > + * @n: the number we're accessing > > > + */ > > > +#define lower_48_bits(n) ((u64)((n) & 0xffffffffffffull)) > > > > why not make this a static inline function? >=20 > Agreed. >=20 > > And visually, it's difficult to quickly count a repeated character to 1= 2. > > > > Perhaps: > > > > static inline u64 lower_48_bits(u64 val) > > { > > =09return val & GENMASK_ULL(47, 0); > > } >=20 > For anyone who has a minimum knowledge of C and hardware your version > is an obsfucated clusterfuck, while the version Keith wrote is trivial > to read. I'd use the explicit: val & ((1ull << 48) - 1) I think it is even fewer characters. =09David. - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)