* Re: [PATCH v14 0/3] of: parsing of multi #{iommu,msi}-cells in maps
[not found] <20260424-parse_iommu_cells-v14-0-fd02f11b6c38@oss.qualcomm.com>
@ 2026-05-06 22:19 ` Rob Herring
0 siblings, 0 replies; only message in thread
From: Rob Herring @ 2026-05-06 22:19 UTC (permalink / raw)
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 Wilczyński, 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, Conor Dooley,
Krzysztof Kozlowski, Prakash Gupta, Vikash Garodia, linux-kernel,
iommu, linux-arm-kernel, devicetree, linux-pci, imx, xen-devel,
linux-arm-msm, Charan Teja Kalla
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
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