Re: [PATCH v8 0/3] of: parsing of multi #{iommu,msi}-cells in maps

[Vijayanand Jitta]

On 2/11/2026 11:10 AM, Vijayanand Jitta wrote:
> So far our parsing of {iommu,msi}-map properites 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.
> 
> [1] https://lore.kernel.org/all/20250627-video_cb-v3-0-51e18c0ffbce@xxxxxxxxxxx/
> 
> V8:
>   Removed mentions of of_map_args from commit message to match code.
> 
>   Link to V7:
>   https://lore.kernel.org/all/20260210101157.2145113-1-vijayanand.jitta@xxxxxxxxxxxxxxxx/
> 
> V7:
>   Removed of_map_id_args structure and replaced it with of_phandle_args as
>   suggested by Dmitry.
> 
>   Link to V6:
>   https://lore.kernel.org/all/20260121055400.937856-1-vijayanand.jitta@xxxxxxxxxxxxxxxx/
> 
> V6:
>   Fixed build error reported by kernel test bot.
> 
>   Link to V5:
>   https://lore.kernel.org/all/20260118181125.1436036-1-vijayanand.jitta@xxxxxxxxxxxxxxxx/
> 
> V5:
>   Fixed Build Warnings.
>   Raised PR for iommu-map dtschema:
>   https://github.com/devicetree-org/dt-schema/pull/184
> 
>   Link to V4:
>   https://lore.kernel.org/all/20251231114257.2382820-1-vijayanand.jitta@xxxxxxxxxxxxxxxx/
> 
> V4:
>   1) Added Reviewed-by tag.
>   2) Resolved warnings reported by kernel test bot, minor code
>   reorganization.
> 
>   Link to V3:
>   https://lore.kernel.org/all/20251221213602.2413124-1-vijayanand.jitta@xxxxxxxxxxxxxxxx/
> 
> V3:
>   1) Added Reviewed-by tag.
>   2) Updated of_map_id_args struct as a wrapper to of_phandle_args and
>   added comment description as suggested by Rob Herring.
> 
>   Link to V2:
>   https://lore.kernel.org/all/20251204095530.8627-1-vijayanand.jitta@xxxxxxxxxxxxxxxx/
> 
> V2:
>   1) Incorporated the patches from Robin that does the clean implementation.
>   2) Dropped the patches the were adding multi-map support from this series
>   as suggested.
> 
> V1:
>  https://lore.kernel.org/all/cover.1762235099.git.charan.kalla@xxxxxxxxxxxxxxxx/
> 
> RFC:
>  https://lore.kernel.org/all/20250928171718.436440-1-charan.kalla@xxxxxxxxxxxxxxxx/#r
> 
> Charan Teja Kalla (1):
>   of: factor arguments passed to of_map_id() into a struct
> 
> Robin Murphy (2):
>   of: Add convenience wrappers for of_map_id()
>   of: Respect #{iommu,msi}-cells in maps
> 
>  drivers/cdx/cdx_msi.c                    |   3 +-
>  drivers/iommu/of_iommu.c                 |   6 +-
>  drivers/irqchip/irq-gic-its-msi-parent.c |   2 +-
>  drivers/of/base.c                        | 148 +++++++++++++++++------
>  drivers/of/irq.c                         |   3 +-
>  drivers/pci/controller/dwc/pci-imx6.c    |  12 +-
>  drivers/pci/controller/pcie-apple.c      |   5 +-
>  drivers/xen/grant-dma-ops.c              |   3 +-
>  include/linux/of.h                       |  33 ++++-
>  9 files changed, 152 insertions(+), 63 deletions(-)
> 


Gentle ping.

Thanks,
Vijay