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 B391AC433EF for ; Tue, 22 Feb 2022 18:43:36 +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: MIME-Version:Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=B5YdwJJyLQiXmOegPA1mIy5KTlcwKP1Sjm1Rcx/DjE0=; b=qX13fjGvgZj87bLpX/C7xqmajy akoWPTNssoz3JIgZRVnTrX7IiUeUZ7blDRDxIYpA32S5qFALsuS1VvARZkIDOLDBPeQrZ/uL6bRXN x7tfiu4TRgLWjVfXJSOrIURlkH1cKmC1jaNpnh18wQA897VELI9JSPWnCX5g5bE+hs4Ft5/SUWpxj z1IMzBGfyhch+xvwIyL8K+Y1OHXRbPPoeZXG3yKF1C+w9tqRP+K/DwetvqYJ1B/vQrwLsgptHeDf9 P+SvfwKssc+4y2Cj/MpAY8OVH/jyizQpeB91BvNaXi/JUU0/ed1NK4/JfyWA8PRvZDvsqU1tfw89C tH8Si2aQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMa8I-00BF26-8X; Tue, 22 Feb 2022 18:43:30 +0000 Received: from relay3.hostedemail.com ([64.99.140.32]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nMa8E-00BF14-TE for linux-nvme@lists.infradead.org; Tue, 22 Feb 2022 18:43:28 +0000 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220222_104327_030741_36C1D294 X-CRM114-Status: GOOD ( 15.07 ) 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 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.