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 E5C3DC433EF for ; Tue, 22 Feb 2022 18:43:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234692AbiBVSnw (ORCPT ); Tue, 22 Feb 2022 13:43:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233516AbiBVSnw (ORCPT ); Tue, 22 Feb 2022 13:43:52 -0500 Received: from relay4.hostedemail.com (relay4.hostedemail.com [64.99.140.36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D45E9E576; Tue, 22 Feb 2022 10:43:26 -0800 (PST) Received: from omf17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 7E08A802C9; Tue, 22 Feb 2022 18:43:24 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: joe@perches.com) by omf17.hostedemail.com (Postfix) with ESMTPA id 5571217; Tue, 22 Feb 2022 18:42:32 +0000 (UTC) Message-ID: <603f9243bb9e1c4c50aaec83a527266b48ab9e20.camel@perches.com> Subject: Re: [PATCHv3 04/10] linux/kernel: introduce lower_48_bits macro From: Joe Perches To: Keith Busch , Christoph Hellwig Cc: 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 10:43:21 -0800 In-Reply-To: <20220222165613.GB1497257@dhcp-10-100-145-180.wdc.com> References: <20220222163144.1782447-1-kbusch@kernel.org> <20220222163144.1782447-5-kbusch@kernel.org> <66a0c8210cf9e7dfcc3fa2d247de1eebd5a8acb7.camel@perches.com> <20220222165045.GA14168@lst.de> <20220222165613.GB1497257@dhcp-10-100-145-180.wdc.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.40.4-1ubuntu2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Stat-Signature: nazzjjx87869o4w9oakhjiahqxjdbban X-Rspamd-Server: rspamout06 X-Rspamd-Queue-Id: 5571217 X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX18aL9+BR2B9Ovzx+56lKMnaVrCxDabIdXo= X-HE-Tag: 1645555352-996125 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Tue, 2022-02-22 at 08:56 -0800, Keith Busch wrote: > On Tue, Feb 22, 2022 at 05:50:45PM +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: > > > > +/ * > > > > + * 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. > > Sure, that sounds good to me. I only did it this way to match the > existing local convention, but I personally prefer the inline function > too. The existing convention is used there to allow the compiler to avoid warnings and unnecessary conversions of a u32 to a u64 when shifting by 32 or more bits. If it's possible to be used with an architecture dependent typedef like dma_addr_t, then perhaps it's reasonable to do something like: #define lower_48_bits(val) \ ({ \ typeof(val) high = lower_16_bits(upper_32_bits(val)); \ typeof(val) low = lower_32_bits(val); \ \ (high << 16 << 16) | low; \ }) and have the compiler have the return value be an appropriate type.