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[2620:137:e000::1:20]) by mx.google.com with ESMTP id 19-20020a631153000000b0042a560b4d30si16689746pgr.500.2022.09.07.07.30.59; Wed, 07 Sep 2022 07:31:12 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@8bytes.org header.s=default header.b=rnWXPfkR; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229576AbiIGOGl (ORCPT + 99 others); Wed, 7 Sep 2022 10:06:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59160 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229884AbiIGOGk (ORCPT ); Wed, 7 Sep 2022 10:06:40 -0400 Received: from mail.8bytes.org (mail.8bytes.org [85.214.250.239]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 6279E9C525; Wed, 7 Sep 2022 07:06:38 -0700 (PDT) Received: from 8bytes.org (p4ff2bb62.dip0.t-ipconnect.de [79.242.187.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.8bytes.org (Postfix) with ESMTPSA id 6118D2409A7; Wed, 7 Sep 2022 16:06:30 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=8bytes.org; s=default; t=1662559591; bh=sD6ntPJavoL+O3jZjBfdlyQKhK42Ee+ATtCC5qSKLek=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rnWXPfkRqiJXCBikZk6JRGP2BockRbTgJPogFW6R24YrO/UYOBdbDIQPctDN3LGpI 79/xXHT61Edm0n+vSGPYdlczsRRfdkacO6KmQgX/Kv6hNnOMuGvxYRlTiNeRqAdoGh 5eisSJGFeEPl9sdwLcPf/+l2Yyy8DviLlelMTM4i/bTvjcSo5ebNKYoIEDQy0YTBKO jt0uBK0fCmoSFWyU5uIRYNcijnnozfeA7oB/uWHePVQatjmPma4sWvhtPveFHkv/Zd 5qGfNEp1V9BqTtR+QMkc0IJeFW1j8U5UpZXX6b1OmgcnRAA8Xu95xNZgC6+l1xfUpO 7YogNayXEccUQ== Date: Wed, 7 Sep 2022 16:06:29 +0200 From: Joerg Roedel To: Jason Gunthorpe Cc: Nicolin Chen , will@kernel.org, robin.murphy@arm.com, alex.williamson@redhat.com, suravee.suthikulpanit@amd.com, marcan@marcan.st, sven@svenpeter.dev, alyssa@rosenzweig.io, robdclark@gmail.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, mjrosato@linux.ibm.com, gerald.schaefer@linux.ibm.com, orsonzhai@gmail.com, baolin.wang@linux.alibaba.com, zhang.lyra@gmail.com, thierry.reding@gmail.com, vdumpa@nvidia.com, jonathanh@nvidia.com, jean-philippe@linaro.org, cohuck@redhat.com, tglx@linutronix.de, shameerali.kolothum.thodi@huawei.com, thunder.leizhen@huawei.com, christophe.jaillet@wanadoo.fr, yangyingliang@huawei.com, jon@solid-run.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-s390@vger.kernel.org, linux-tegra@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, kevin.tian@intel.com Subject: Re: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group Message-ID: References: <20220815181437.28127-1-nicolinc@nvidia.com> <20220815181437.28127-2-nicolinc@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 07, 2022 at 10:47:39AM -0300, Jason Gunthorpe wrote: > Would you be happier if we wrote it like > > #define IOMMU_EINCOMPATIBLE_DEVICE xx > > Which tells "which of the function parameters is actually invalid" ? Having done some Rust hacking in the last months, I have to say I like to concept of error handling with Result<> there. Ideally we have a way to emulate that in our C code without having to change all callers. What I am proposing is a way this could be emulated here, but I am open to other suggestions. Still better than re-using random error codes for special purposes. Regards, Joerg