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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 494DFECE587 for ; Tue, 15 Oct 2019 07:31:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20DD62086A for ; Tue, 15 Oct 2019 07:31:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727607AbfJOHbJ (ORCPT ); Tue, 15 Oct 2019 03:31:09 -0400 Received: from verein.lst.de ([213.95.11.211]:53271 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725710AbfJOHbJ (ORCPT ); Tue, 15 Oct 2019 03:31:09 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id E7CF568B05; Tue, 15 Oct 2019 09:31:04 +0200 (CEST) Date: Tue, 15 Oct 2019 09:31:04 +0200 From: Christoph Hellwig To: Robin Murphy Cc: David Gibson , Ram Pai , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@ozlabs.org, mdroth@linux.vnet.ibm.com, aik@linux.ibm.com, paul.burton@mips.com, b.zolnierkie@samsung.com, m.szyprowski@samsung.com, hch@lst.de, jasowang@redhat.com, andmike@us.ibm.com, sukadev@linux.vnet.ibm.com Subject: Re: [PATCH 1/2] dma-mapping: Add dma_addr_is_phys_addr() Message-ID: <20191015073104.GA32252@lst.de> References: <1570843519-8696-1-git-send-email-linuxram@us.ibm.com> <1570843519-8696-2-git-send-email-linuxram@us.ibm.com> <20191014045139.GN4080@umbus.fritz.box> <37609731-5539-b906-aa94-2ef0242795ac@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37609731-5539-b906-aa94-2ef0242795ac@arm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 14, 2019 at 11:29:24AM +0100, Robin Murphy wrote: >> However, I would like to see the commit message (and maybe the inline >> comments) expanded a bit on what the distinction here is about. Some >> of the text from the next patch would be suitable, about DMA addresses >> usually being in a different address space but not in the case of >> bounce buffering. > > Right, this needs a much tighter definition. "DMA address happens to be a > valid physical address" is true of various IOMMU setups too, but I can't > believe it's meaningful in such cases. > > If what you actually want is "DMA is direct or SWIOTLB" - i.e. "DMA address > is physical address of DMA data (not necessarily the original buffer)" - > wouldn't dma_is_direct() suffice? It would. But drivers have absolutely no business knowing any of this.