Subject: Re: [PATCH v9 1/3] of: Add convenience wrappers for of_map_id()

From: Rob Herring <[email-masked]>
Date: Thu, 5 Mar 2026 15:47:20 -0600

On Wed, Mar 04, 2026 at 03:02:14PM +0530, Vijayanand Jitta wrote:
> 
> 
> On 3/1/2026 3:16 PM, Marc Zyngier wrote:
> > On Sun, 01 Mar 2026 08:34:19 +0000,
> > Vijayanand Jitta <[email-masked]> wrote:
> >>
> >> From: Robin Murphy <[email-masked]>
> >>
> >> Since we now have quite a few users parsing "iommu-map" and "msi-map"
> >> properties, give them some wrappers to conveniently encapsulate the
> >> appropriate sets of property names. This will also make it easier to
> >> then change of_map_id() to correctly account for specifier cells.
> >>
> >> Reviewed-by: Rob Herring (Arm) <[email-masked]>
> >> Reviewed-by: Frank Li <[email-masked]>
> >> Signed-off-by: Robin Murphy <[email-masked]>
> >> Signed-off-by: Vijayanand Jitta <[email-masked]>
> >> ---
> >>  drivers/cdx/cdx_msi.c                    |  3 +--
> >>  drivers/iommu/of_iommu.c                 |  4 +---
> >>  drivers/irqchip/irq-gic-its-msi-parent.c |  2 +-
> >>  drivers/of/irq.c                         |  3 +--
> >>  drivers/pci/controller/dwc/pci-imx6.c    |  6 ++----
> >>  drivers/pci/controller/pcie-apple.c      |  3 +--
> >>  drivers/xen/grant-dma-ops.c              |  3 +--
> >>  include/linux/of.h                       | 14 ++++++++++++++
> >>  8 files changed, 22 insertions(+), 16 deletions(-)
> >>
> >> diff --git a/drivers/cdx/cdx_msi.c b/drivers/cdx/cdx_msi.c
> >> index 91b95422b263..63b3544ec997 100644
> >> --- a/drivers/cdx/cdx_msi.c
> >> +++ b/drivers/cdx/cdx_msi.c
> >> @@ -128,8 +128,7 @@ static int cdx_msi_prepare(struct irq_domain *msi_domain,
> >>  	int ret;
> >>  
> >>  	/* Retrieve device ID from requestor ID using parent device */
> >> -	ret = of_map_id(parent->of_node, cdx_dev->msi_dev_id, "msi-map", "msi-map-mask",
> >> -			NULL, &dev_id);
> >> +	ret = of_map_msi_id(parent->of_node, cdx_dev->msi_dev_id, NULL, &dev_id);
> >>  	if (ret) {
> >>  		dev_err(dev, "of_map_id failed for MSI: %d\n", ret);
> >>  		return ret;
> >> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> >> index 6b989a62def2..a511ecf21fcd 100644
> >> --- a/drivers/iommu/of_iommu.c
> >> +++ b/drivers/iommu/of_iommu.c
> >> @@ -48,9 +48,7 @@ static int of_iommu_configure_dev_id(struct device_node *master_np,
> >>  	struct of_phandle_args iommu_spec = { .args_count = 1 };
> >>  	int err;
> >>  
> >> -	err = of_map_id(master_np, *id, "iommu-map",
> >> -			 "iommu-map-mask", &iommu_spec.np,
> >> -			 iommu_spec.args);
> >> +	err = of_map_iommu_id(master_np, *id, &iommu_spec.np, iommu_spec.args);
> >>  	if (err)
> >>  		return err;
> >>  
> >> diff --git a/drivers/irqchip/irq-gic-its-msi-parent.c b/drivers/irqchip/irq-gic-its-msi-parent.c
> >> index d36b278ae66c..b63343a227a9 100644
> >> --- a/drivers/irqchip/irq-gic-its-msi-parent.c
> >> +++ b/drivers/irqchip/irq-gic-its-msi-parent.c
> >> @@ -180,7 +180,7 @@ static int of_pmsi_get_msi_info(struct irq_domain *domain, struct device *dev, u
> >>  
> >>  	struct device_node *msi_ctrl __free(device_node) = NULL;
> >>  
> >> -	return of_map_id(dev->of_node, dev->id, "msi-map", "msi-map-mask", &msi_ctrl, dev_id);
> >> +	return of_map_msi_id(dev->of_node, dev->id, &msi_ctrl, dev_id);
> >>  }
> >>  
> >>  static int its_pmsi_prepare(struct irq_domain *domain, struct device *dev,
> >> diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> >> index 6367c67732d2..e37c1b3f8736 100644
> >> --- a/drivers/of/irq.c
> >> +++ b/drivers/of/irq.c
> >> @@ -817,8 +817,7 @@ u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in)
> >>  	 * "msi-map" or an "msi-parent" property.
> >>  	 */
> >>  	for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent) {
> >> -		if (!of_map_id(parent_dev->of_node, id_in, "msi-map",
> >> -				"msi-map-mask", msi_np, &id_out))
> >> +		if (!of_map_msi_id(parent_dev->of_node, id_in, msi_np, &id_out))
> >>  			break;
> >>  		if (!of_check_msi_parent(parent_dev->of_node, msi_np))
> >>  			break;
> >> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> >> index a5b8d0b71677..bff8289f804a 100644
> >> --- a/drivers/pci/controller/dwc/pci-imx6.c
> >> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> >> @@ -1144,8 +1144,7 @@ static int imx_pcie_add_lut_by_rid(struct imx_pcie *imx_pcie, u32 rid)
> >>  	u32 sid = 0;
> >>  
> >>  	target = NULL;
> >> -	err_i = of_map_id(dev->of_node, rid, "iommu-map", "iommu-map-mask",
> >> -			  &target, &sid_i);
> >> +	err_i = of_map_iommu_id(dev->of_node, rid, &target, &sid_i);
> >>  	if (target) {
> >>  		of_node_put(target);
> >>  	} else {
> >> @@ -1158,8 +1157,7 @@ static int imx_pcie_add_lut_by_rid(struct imx_pcie *imx_pcie, u32 rid)
> >>  	}
> >>  
> >>  	target = NULL;
> >> -	err_m = of_map_id(dev->of_node, rid, "msi-map", "msi-map-mask",
> >> -			  &target, &sid_m);
> >> +	err_m = of_map_msi_id(dev->of_node, rid, &target, &sid_m);
> >>  
> >>  	/*
> >>  	 *   err_m      target
> >> diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> >> index 2d92fc79f6dd..a0937b7b3c4d 100644
> >> --- a/drivers/pci/controller/pcie-apple.c
> >> +++ b/drivers/pci/controller/pcie-apple.c
> >> @@ -764,8 +764,7 @@ static int apple_pcie_enable_device(struct pci_host_bridge *bridge, struct pci_d
> >>  	dev_dbg(&pdev->dev, "added to bus %s, index %d\n",
> >>  		pci_name(pdev->bus->self), port->idx);
> >>  
> >> -	err = of_map_id(port->pcie->dev->of_node, rid, "iommu-map",
> >> -			"iommu-map-mask", NULL, &sid);
> >> +	err = of_map_iommu_id(port->pcie->dev->of_node, rid, NULL, &sid);
> >>  	if (err)
> >>  		return err;
> >>  
> >> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> >> index c2603e700178..1b7696b2d762 100644
> >> --- a/drivers/xen/grant-dma-ops.c
> >> +++ b/drivers/xen/grant-dma-ops.c
> >> @@ -325,8 +325,7 @@ static int xen_dt_grant_init_backend_domid(struct device *dev,
> >>  		struct pci_dev *pdev = to_pci_dev(dev);
> >>  		u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
> >>  
> >> -		if (of_map_id(np, rid, "iommu-map", "iommu-map-mask", &iommu_spec.np,
> >> -				iommu_spec.args)) {
> >> +		if (of_map_iommu_id(np, rid, &iommu_spec.np, iommu_spec.args)) {
> >>  			dev_dbg(dev, "Cannot translate ID\n");
> >>  			return -ESRCH;
> >>  		}
> >> diff --git a/include/linux/of.h b/include/linux/of.h
> >> index be6ec4916adf..824649867810 100644
> >> --- a/include/linux/of.h
> >> +++ b/include/linux/of.h
> >> @@ -1457,6 +1457,20 @@ static inline int of_property_read_s32(const struct device_node *np,
> >>  	return of_property_read_u32(np, propname, (u32*) out_value);
> >>  }
> >>  
> >> +static inline int of_map_iommu_id(const struct device_node *np, u32 id,
> >> +				  struct device_node **target, u32 *id_out)
> >> +{
> >> +	return of_map_id(np, id, "iommu-map", "iommu-map-mask",
> >> +			 target, id_out);
> >> +}
> >> +
> >> +static inline int of_map_msi_id(const struct device_node *np, u32 id,
> >> +				struct device_node **target, u32 *id_out)
> >> +{
> >> +	return of_map_id(np, id, "msi-map", "msi-map-mask",
> >> +			 target, id_out);
> >> +}
> >> +
> > 
> > Any particular reason why this is made inline instead of out of line
> > in of/base.c? Also, some documentation would be helpful for the
> > aspiring hackers dipping into this.
> > 
> > Other than that,
> > 
> > Acked-by: Marc Zyngier <[email-masked]>
> > 
> > 	M.
> > 
> 
> Thanks Marc.
> 
> I made them static inline mainly because they’re just trivial wrappers
> around of_map_id(), so keeping them in include/linux/of.h avoids adding
> new global symbols/exports and keeps the callsites simple (similar to
> the existing of_property_read_*() inline wrappers).
> 
> That said, I don’t have a strong preference—if you’d rather have
> out-of-line helpers in drivers/of/base.c, I’m happy to respin accordingly.

The downside is we get N copies of the string args for N callers 
assuming the callers are in different compilation units. It's not 
performance critical either.

Rob