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=-5.3 required=3.0 tests=BAYES_00, 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 B158DC4363D for ; Fri, 25 Sep 2020 04:14:35 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 2EDA221D20 for ; Fri, 25 Sep 2020 04:14:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2EDA221D20 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id CEF5F86CE1; Fri, 25 Sep 2020 04:14:34 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id bPpJAB+6RkHA; Fri, 25 Sep 2020 04:14:33 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id C551C86C59; Fri, 25 Sep 2020 04:14:33 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 9B07FC0890; Fri, 25 Sep 2020 04:14:33 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id ED1BCC0859 for ; Fri, 25 Sep 2020 04:14:31 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id E712A85267 for ; Fri, 25 Sep 2020 04:14:31 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GmalGiBcqAPD for ; Fri, 25 Sep 2020 04:14:30 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 9B73784DD5 for ; Fri, 25 Sep 2020 04:14:30 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 0871E68AFE; Fri, 25 Sep 2020 06:14:26 +0200 (CEST) Date: Fri, 25 Sep 2020 06:14:25 +0200 From: 'Christoph Hellwig' To: David Laight Subject: Re: [PATCH 3/3] dma-mapping: better document dma_addr_t and DMA_MAPPING_ERROR Message-ID: <20200925041425.GA9419@lst.de> References: <20200922134002.1227279-1-hch@lst.de> <20200922134002.1227279-4-hch@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Cc: "iommu@lists.linux-foundation.org" , 'Christoph Hellwig' , Dominik Brodowski , "linux-kernel@vger.kernel.org" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Tue, Sep 22, 2020 at 01:56:46PM +0000, David Laight wrote: > > +/* > > + * A dma_addr_t can hold any valid DMA or bus address for the platform. It can > > + * be given to a device to use as a DMA source or target. A CPU cannot > > + * reference a dma_addr_t directly because there may be translation between its > > + * physical address space and the bus address space. > > It can't access it 'directly' because it isn't a virtual address.... > > > + * > > + * DMA_MAPPING_ERROR is the magic error code if a mapping failed. It should not > > + * be used directly in drivers, but checked for using dma_mapping_error() > > + * instead. > > + */ > > I think it might be worth adding: > > A dma_addr_t value may be device dependant and differ from the > 'physical address' of the memory. This is what I've committed: * A dma_addr_t can hold any valid DMA or bus address for the platform. It can * be given to a device to use as a DMA source or target. It is specific to a * given device and there may be a translation between the CPU physical address * space and the bus address space. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu