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.
The motivation for this patchset originates from the multi-map use case
described in V1, which will be addressed in a subsequent series once the
current fixes for iommu-cell handling are concluded.
These changes have been tested on QEMU for the arm64 architecture. We
plan to perform more extensive testing based on community feedback.
[1] https://lore.kernel.org/all/20250627-video_cb-v3-0-51e18c0ffbce@quicinc.com/
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@oss.qualcomm.com/
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@oss.qualcomm.com/
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@oss.qualcomm.com/
RFC:
https://lore.kernel.org/all/20250928171718.436440-1-charan.kalla@oss.qualcomm.com/#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 | 12 +-
drivers/irqchip/irq-gic-its-msi-parent.c | 4 +-
drivers/of/base.c | 145 +++++++++++++++++------
drivers/of/irq.c | 3 +-
drivers/pci/controller/dwc/pci-imx6.c | 10 +-
drivers/pci/controller/pcie-apple.c | 6 +-
drivers/xen/grant-dma-ops.c | 21 ++--
include/linux/of.h | 36 +++++-
9 files changed, 169 insertions(+), 71 deletions(-)
--
2.34.1