From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: remove the ->mapping_error method from dma_map_ops V2 Date: Thu, 29 Nov 2018 19:31:32 +0100 Message-ID: <20181129183132.GA30281@lst.de> References: <20181123065511.GA17856@lst.de> <20181128074117.GA21126@lst.de> <20181128174545.GJ30658@n2100.armlinux.org.uk> <20181128180841.GM30658@n2100.armlinux.org.uk> <20181129162323.GA27068@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Linus Torvalds Cc: Christoph Hellwig , Russell King - ARM Linux , linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, robin.murphy@arm.com, the arch/x86 maintainers , Linux List Kernel Mailing , iommu@lists.linux-foundation.org, linux-alpha@vger.kernel.org, xen-devel@lists.xenproject.org, David Woodhouse , linux-arm-kernel@lists.infradead.org List-Id: linux-arch.vger.kernel.org On Thu, Nov 29, 2018 at 09:44:05AM -0800, Linus Torvalds wrote: > No. Really. If there's no iotlb, then you just mark that one page > reserved. It simply doesn't get used. It doesn't mean you suddenly > need a swiotlb. Sure, we could just skip that page entirely based on dma_to_phys. > But whatever. It's independent from the patch series under discussion. > Make dma_mapping_error() at least return a real error (eg -EINVAL, or > whatever is the common error), and we can maybe do this later. Ok, I'll do that. > Or, better yet, plan on removing the single-page dma mappign entirely > at a later date, and make the issue moot. What would be the replacement? Build a S/G list for every single page mapping? Not sure that would create a lot of happy campers.. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:45479 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728348AbeK3Fhw (ORCPT ); Fri, 30 Nov 2018 00:37:52 -0500 Date: Thu, 29 Nov 2018 19:31:32 +0100 From: Christoph Hellwig Subject: Re: remove the ->mapping_error method from dma_map_ops V2 Message-ID: <20181129183132.GA30281@lst.de> References: <20181123065511.GA17856@lst.de> <20181128074117.GA21126@lst.de> <20181128174545.GJ30658@n2100.armlinux.org.uk> <20181128180841.GM30658@n2100.armlinux.org.uk> <20181129162323.GA27068@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: Christoph Hellwig , Russell King - ARM Linux , linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, robin.murphy@arm.com, the arch/x86 maintainers , Linux List Kernel Mailing , iommu@lists.linux-foundation.org, linux-alpha@vger.kernel.org, xen-devel@lists.xenproject.org, David Woodhouse , linux-arm-kernel@lists.infradead.org Message-ID: <20181129183132.JZSNReep179ZoL3ZDsBecTeKf6OL7OMLXKT2--7Stqc@z> On Thu, Nov 29, 2018 at 09:44:05AM -0800, Linus Torvalds wrote: > No. Really. If there's no iotlb, then you just mark that one page > reserved. It simply doesn't get used. It doesn't mean you suddenly > need a swiotlb. Sure, we could just skip that page entirely based on dma_to_phys. > But whatever. It's independent from the patch series under discussion. > Make dma_mapping_error() at least return a real error (eg -EINVAL, or > whatever is the common error), and we can maybe do this later. Ok, I'll do that. > Or, better yet, plan on removing the single-page dma mappign entirely > at a later date, and make the issue moot. What would be the replacement? Build a S/G list for every single page mapping? Not sure that would create a lot of happy campers..