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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B1C4C433DB for ; Tue, 16 Mar 2021 08:01:01 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 159D160240 for ; Tue, 16 Mar 2021 08:01:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 159D160240 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=jBMommuIyVjA2uodu7sdDsjGQ9uhbM8i7TrgJuVgPpc=; b=qr5RjzwWJRXr3JZPhYBi2zueC Jde/q/TzxSwyhlXjmFqxV4Pthw+dL51I3dLeFUxw6bKoMyH2pIYbGnkGt/Ns2qbhvsezMA+6rqEWa 0GiYcajrcaJa5rYdjwkS6bDgiqlouw6wGivJgaNu8aGliMMLRhCMlIStgRUgCugXDr/hd9YIvgdXK 7psVuT7fKGzemY7UM0aqHEh4o37fpnzYOhUbMOJr3E2kK8a5MEu1tS0R1SaNOfw+NOP+LsJpgTR/E 74/y3ZEnFyJqFxz+OFbl1wu25+OaX/Z9jSlL2D58eDrFowpK5EJEDlSEyMZNkOZzouKOib+bndudP Ma3x+eJAQ==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lM4d9-0003Jr-5h; Tue, 16 Mar 2021 08:00:43 +0000 Received: from verein.lst.de ([213.95.11.211]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lM4cg-0003Bh-OG for linux-nvme@lists.infradead.org; Tue, 16 Mar 2021 08:00:17 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 75A4D68C4E; Tue, 16 Mar 2021 09:00:09 +0100 (CET) Date: Tue, 16 Mar 2021 09:00:08 +0100 From: Christoph Hellwig To: Logan Gunthorpe Cc: Ira Weiny , linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , Christian =?iso-8859-1?Q?K=F6nig?= , Ira Weiny , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin Subject: Re: [RFC PATCH v2 07/11] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support Message-ID: <20210316080008.GC15949@lst.de> References: <20210311233142.7900-1-logang@deltatee.com> <20210311233142.7900-8-logang@deltatee.com> <20210313023657.GC3402637@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210316_080015_546564_9872F71D X-CRM114-Status: GOOD ( 16.36 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Mon, Mar 15, 2021 at 10:33:13AM -0600, Logan Gunthorpe wrote: > >> + return !ops || ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED; > > > > Is this logic correct? I would have expected. > > > > return (ops && ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED); > > > If ops is NULL then the operations in kernel/dma/direct.c are used and > support is added to those in patch 6. So it is correct as written. It is not quite that easy. There also is the bypass flag and for the specific case where that is ignored the code needs a really good comment. And to assist that formatted so that it makes sense. The above line is indeed highly confusing even if it ends up being correct. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme