From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7E6172139C9; Tue, 26 May 2026 06:12:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779775949; cv=none; b=ZNBRBYynJiYlg6/W+vFDvsWwRJZytsrt1CW7W2Z/lYOhTwsk+7znv6GtQFMSPn9KqJZ/RP60maworOqS9Rl+pAOBuX1NXrxWXgXoAxbGBTV8lVpcWCnzU8PvU6KP8LBvBjiuIUq9HIMPm3W69XEyKzCXJf/n1hmX+WPPcNvzOyE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779775949; c=relaxed/simple; bh=yghNJcQrkYUWWNbAKrpBz58BflQIvrggSW45MBSWtH4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=q32VmntnZDOgPomUb0Mvx8smp5o/4XtDAxMSwI9sQX577RRURwCcRdFhTO2a+zD7q18B+BusGsdS9RsDI0VGvsPn4KAV/ErU6jivKVjjo6baT4iQslhL/WLw+9omulWgIXJcV0RqV2GWw/+GXJOmI3tKMUIcHKsM496uWSTn8rg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PaNxY70+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PaNxY70+" 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> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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> 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