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, 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 4FF9AC433DF for ; Tue, 25 Aug 2020 13:26:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1822B20639 for ; Tue, 25 Aug 2020 13:26:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1822B20639 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 814AB6B0002; Tue, 25 Aug 2020 09:26:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7C4CE6B000D; Tue, 25 Aug 2020 09:26:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 701036B000E; Tue, 25 Aug 2020 09:26:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0075.hostedemail.com [216.40.44.75]) by kanga.kvack.org (Postfix) with ESMTP id 5A9C76B0002 for ; Tue, 25 Aug 2020 09:26:17 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id F20B58248047 for ; Tue, 25 Aug 2020 13:26:16 +0000 (UTC) X-FDA: 77189164752.02.nest92_230ce972705c Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id C99F610097AA1 for ; Tue, 25 Aug 2020 13:26:16 +0000 (UTC) X-HE-Tag: nest92_230ce972705c X-Filterd-Recvd-Size: 2269 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Tue, 25 Aug 2020 13:26:16 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 6E33E68BEB; Tue, 25 Aug 2020 15:26:12 +0200 (CEST) Date: Tue, 25 Aug 2020 15:26:12 +0200 From: Christoph Hellwig To: Marek Szyprowski Cc: Christoph Hellwig , Mauro Carvalho Chehab , Thomas Bogendoerfer , "James E.J. Bottomley" , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Ben Skeggs , Pawel Osciak , Matt Porter , iommu@lists.linux-foundation.org, Tom Lendacky , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-samsung-soc@vger.kernel.org, nouveau@lists.freedesktop.org, netdev@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org, alsa-devel@alsa-project.org Subject: Re: a saner API for allocating DMA addressable pages Message-ID: <20200825132612.GA22318@lst.de> References: <20200819065555.1802761-1-hch@lst.de> <8fa1ce36-c783-1a02-6890-211eb504a33b@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8fa1ce36-c783-1a02-6890-211eb504a33b@samsung.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: C99F610097AA1 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 25, 2020 at 01:30:41PM +0200, Marek Szyprowski wrote: > I really wonder what is the difference between this new API and > alloc_pages(GFP_DMA, n). Is this API really needed? I thought that this > is legacy thing to be removed one day... The difference is that the pages returned are guranteed to be addressable by the devie. This is a very important difference that matters for a lot of use cases.