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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRl1l-000000018ek-0Stx; Tue, 26 May 2026 06:12:33 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wRl1h-000000018e0-2GuW for linux-arm-kernel@lists.infradead.org; Tue, 26 May 2026 06:12:30 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 77E7A437B8; Tue, 26 May 2026 06:12:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3D341F000E9; Tue, 26 May 2026 06:12:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779775948; bh=C4Q6K7bbOoVpU1MwP5UtVcbQqMSK8GB1uvqgVWAyIgA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=PaNxY70+YMonEMLTIazGO/O55U8XOU9hI8Sd6x+lIwRz+krY7I2MIFVP2TtWHQRk6 oLs6o/MlXIoueCpSrWzl4/TP61gPF+HN/xvzZ2vYpOcuWB0Dm95zHR9huRUsF9V+Hf YnTyB9za+3uCaHbFr+R2wcRewXry6G17iicxgZkjKeAXoiSONhiO8kf+vbI4ljsIDR 1fy3F+EBJAgg0t5T5mg4+PsdSDHbAEaAyRvnVetK1IwZ8UztJCg6MOoYJa1oLvRi7m 9dhRl/AKdtuVr7cjGvsAMXrJhl9YyIGQK1PcdmnOV19LefKY14Nezbe0MAE8vRqjtb Xzj2xjTt805IA== Date: Tue, 26 May 2026 08:12:26 +0200 From: Krzysztof Kozlowski To: Vijayanand Jitta Cc: Nipun Gupta , Nikhil Agarwal , Joerg Roedel , Will Deacon , Robin Murphy , Marc Zyngier , Lorenzo Pieralisi , Thomas Gleixner , Saravana Kannan , Richard Zhu , Lucas Stach , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Manivannan Sadhasivam , Bjorn Helgaas , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dmitry Baryshkov , Konrad Dybcio , Bjorn Andersson , Rob Herring , Conor Dooley , Krzysztof Kozlowski , Prakash Gupta , Vikash Garodia , linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, imx@lists.linux.dev, xen-devel@lists.xenproject.org, linux-arm-msm@vger.kernel.org, Charan Teja Kalla Subject: Re: [PATCH v15 0/3] of: parsing of multi #{iommu,msi}-cells in maps Message-ID: <20260526-finicky-crafty-hare-eae27c@quoll> References: <20260520-parse_iommu_cells-v15-0-b5f99ad4e7e8@oss.qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260520-parse_iommu_cells-v15-0-b5f99ad4e7e8@oss.qualcomm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260525_231229_753826_68CFEA23 X-CRM114-Status: GOOD ( 19.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 20, 2026 at 01:32:39PM +0530, Vijayanand Jitta wrote: > So far our parsing of {iommu,msi}-map properties has always blindly > assumed that the output specifiers will always have exactly 1 cell. > This typically does happen to be the case, but is not actually enforced > (and the PCI msi-map binding even explicitly states support for 0 or 1 > cells) - as a result we've now ended up with dodgy DTs out in the field > which depend on this behaviour to map a 1-cell specifier for a 2-cell > provider, despite that being bogus per the bindings themselves. > > Since there is some potential use[1] in being able to map at least > single input IDs to multi-cell output specifiers (and properly support > 0-cell outputs as well), add support for properly parsing and using the > target nodes' #cells values, albeit with the unfortunate complication of > still having to work around expectations of the old behaviour too. > -- Robin. > > Unlike single #{}-cell, it is complex to establish a linear relation > between input 'id' and output specifier for multi-cell properties, thus > it is always expected that len never going to be > 1. > > These changes have been tested on QEMU for the arm64 architecture. So there is no real user for that. That's unconvincing. I would assume that at least you have real user where you test it. If you want to speed up acceptance of your patches, then also I would prefer to see at least one more user, beside Qualcomm. IOW, show how you solve other people problems, not only yours. Best regards, Krzysztof