From: Rob Herring <robh@kernel.org>
To: Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>
Cc: "Nipun Gupta" <nipun.gupta@amd.com>,
"Nikhil Agarwal" <nikhil.agarwal@amd.com>,
"Joerg Roedel" <joro@8bytes.org>, "Will Deacon" <will@kernel.org>,
"Robin Murphy" <robin.murphy@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Thomas Gleixner" <tglx@kernel.org>,
"Saravana Kannan" <saravanak@kernel.org>,
"Richard Zhu" <hongxing.zhu@nxp.com>,
"Lucas Stach" <l.stach@pengutronix.de>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
"Manivannan Sadhasivam" <mani@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Frank Li" <Frank.Li@nxp.com>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
"Pengutronix Kernel Team" <kernel@pengutronix.de>,
"Fabio Estevam" <festevam@gmail.com>,
"Juergen Gross" <jgross@suse.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
"Dmitry Baryshkov" <dmitry.baryshkov@oss.qualcomm.com>,
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"Conor Dooley" <conor+dt@kernel.org>,
"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
"Prakash Gupta" <prakash.gupta@oss.qualcomm.com>,
"Vikash Garodia" <vikash.garodia@oss.qualcomm.com>,
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" <charan.kalla@oss.qualcomm.com>
Subject: Re: [PATCH v14 0/3] of: parsing of multi #{iommu,msi}-cells in maps
Date: Wed, 6 May 2026 17:19:15 -0500 [thread overview]
Message-ID: <20260506221915.GA3290640-robh@kernel.org> (raw)
In-Reply-To: <20260424-parse_iommu_cells-v14-0-fd02f11b6c38@oss.qualcomm.com>
On Fri, Apr 24, 2026 at 11:26:07AM +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.
>
> Since, this would also need update in dt-schema, raised PR[2] for the
> same.
Sashiko has some thoughts on the series:
https://sashiko.dev/#/patchset/20260424-parse_iommu_cells-v14-0-fd02f11b6c38%40oss.qualcomm.com
Rob
prev parent reply other threads:[~2026-05-06 22:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-24 5:56 [PATCH v14 0/3] of: parsing of multi #{iommu,msi}-cells in maps Vijayanand Jitta
2026-04-24 5:56 ` [PATCH v14 1/3] of: Add convenience wrappers for of_map_id() Vijayanand Jitta
2026-04-24 5:56 ` [PATCH v14 2/3] of: Factor arguments passed to of_map_id() into a struct Vijayanand Jitta
2026-04-24 5:56 ` [PATCH v14 3/3] of: Respect #{iommu,msi}-cells in maps Vijayanand Jitta
2026-05-06 22:19 ` Rob Herring [this message]
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