PCI/MSI: Add pci_msi_map_rid_ctlr_node() helper function

IRQchip drivers need a PCI/MSI function to map a RID to a MSI
controller deviceID namespace and at the same time retrieve the
struct device_node pointer of the MSI controller the RID is mapped
to.

Add pci_msi_map_rid_ctlr_node() to achieve this purpose.

Cc  Bjorn Helgaas <bhelgaas@google.com>

Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250703-gicv5-host-v7-25-12e71f1b3528@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Lorenzo Pieralisi

drivers/pci/msi/irqdomain.c

@@ -427,6 +427,26 @@ u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
 	return rid;
 }
 
+/**
+ * pci_msi_map_rid_ctlr_node - Get the MSI controller node and MSI requester id (RID)
+ * @pdev:	The PCI device
+ * @node:	Pointer to store the MSI controller device node
+ *
+ * Use the firmware data to find the MSI controller node for @pdev.
+ * If found map the RID and initialize @node with it. @node value must
+ * be set to NULL on entry.
+ *
+ * Returns: The RID.
+ */
+u32 pci_msi_map_rid_ctlr_node(struct pci_dev *pdev, struct device_node **node)
+{
+	u32 rid = pci_dev_id(pdev);
+
+	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
+
+	return of_msi_xlate(&pdev->dev, node, rid);
+}
+
 /**
  * pci_msi_get_device_domain - Get the MSI domain for a given PCI device
  * @pdev:	The PCI device

include/linux/msi.h

@@ -705,6 +705,7 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
 					     struct msi_domain_info *info,
 					     struct irq_domain *parent);
 u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
+u32 pci_msi_map_rid_ctlr_node(struct pci_dev *pdev, struct device_node **node);
 struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
 #else /* CONFIG_PCI_MSI */
 static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)