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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1252CC433F5 for ; Tue, 22 Feb 2022 16:59:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234433AbiBVQ71 (ORCPT ); Tue, 22 Feb 2022 11:59:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232105AbiBVQ70 (ORCPT ); Tue, 22 Feb 2022 11:59:26 -0500 Received: from relay4.hostedemail.com (relay4.hostedemail.com [64.99.140.37]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3717B16C4D7 for ; Tue, 22 Feb 2022 08:59:00 -0800 (PST) Received: from omf09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id B256D120966; Tue, 22 Feb 2022 16:58:58 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: joe@perches.com) by omf09.hostedemail.com (Postfix) with ESMTPA id DCE9720028; Tue, 22 Feb 2022 16:58:56 +0000 (UTC) Message-ID: <38d356c2ea0cd9c8cec1e6377793b5c465eca889.camel@perches.com> Subject: Re: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro From: Joe Perches To: Christoph Hellwig 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 Date: Tue, 22 Feb 2022 08:58:56 -0800 In-Reply-To: <20220222165045.GA14168@lst.de> References: <20220222163144.1782447-1-kbusch@kernel.org> <20220222163144.1782447-5-kbusch@kernel.org> <66a0c8210cf9e7dfcc3fa2d247de1eebd5a8acb7.camel@perches.com> <20220222165045.GA14168@lst.de> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.40.4-1ubuntu2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspamout05 X-Rspamd-Queue-Id: DCE9720028 X-Stat-Signature: bk4jafjtuowkr7tuxqe1os9d7x7ekmx4 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX187kE9xU/fonTPBMMbSmL7JTFcT++IlEDc= X-HE-Tag: 1645549136-753137 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, 2022-02-22 at 17:50 +0100, Christoph Hellwig wrote: > 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 @@ > > > } \ > > > ) > > > > > > +/** > > > + * 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? > > Agreed. > > > And visually, it's difficult to quickly count a repeated character to 12. > > > > Perhaps: > > > > static inline u64 lower_48_bits(u64 val) > > { > > return val & GENMASK_ULL(47, 0); > > } > > 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. Don't think so. I've dealt with hardware and have more than once seen defects introduced by firmware developers that can't count. be quick, which one is it: 0xfffffffffffULL or 0xffffffffffffULL or 0xfffffffffffffULL or 0xffffffffffffffULL