Re: [PATCH v2 4/7] PCI/MSI: Make the pci_msi_map_rid_ctlr_node() interface firmware agnostic

Jonathan Cameron
2026-01-05T12:21:18Z

On Thu, 18 Dec 2025 11:14:30 +0100
Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:

> To support booting with OF and ACPI seamlessly, GIC ITS parent code
> requires the PCI/MSI irqdomain layer to implement a function to retrieve
> an MSI controller fwnode and map an RID in a firmware agnostic way
> (ie pci_msi_map_rid_ctlr_node()).
>
> Convert pci_msi_map_rid_ctlr_node() to an OF agnostic interface
> (fwnode_handle based) and update the GIC ITS MSI parent code to reflect
> the pci_msi_map_rid_ctlr_node() change.
>
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Marc Zyngier <maz@kernel.org>
Hi Lorenzo,

A few minor comments inline. All in the 'up to you' category.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---

> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index a329060287b5..3136341e802c 100644
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -376,23 +376,35 @@ u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
> }
>
> /**
> - * pci_msi_map_rid_ctlr_node - Get the MSI controller node and MSI requester id (RID)
> + * pci_msi_map_rid_ctlr_node - Get the MSI controller fwnode_handle and MSI requester id (RID)
> + * @domain: The interrupt domain
> * @pdev: The PCI device
> - * @node: Pointer to store the MSI controller device node
> + * @node: Pointer to store the MSI controller fwnode_handle
> *
> - * Use the firmware data to find the MSI controller node for @pdev.
> + * Use the firmware data to find the MSI controller fwnode_handle 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 pci_msi_map_rid_ctlr_node(struct irq_domain *domain, struct pci_dev *pdev,
> + struct fwnode_handle **node)
> {
> + struct device_node *of_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);
> + of_node = irq_domain_get_of_node(domain);
> + if (of_node) {

I haven't read on but my assumption is of_node is never used for anything else.
I'd make that explicit by not having the local variable.
if (irq_domain_get_of_node(domain))

Might even be worth a comment to say this is just checking of is in use for the
domain in general?

> + struct device_node *msi_ctlr_node = NULL;
> +
> + rid = of_msi_xlate(&pdev->dev, &msi_ctlr_node, rid);
> + if (msi_ctlr_node)

Do you need the protection? Ultimately that depends on whether
setting *node = NULL on failure to match is a problem.
It's a bit subtle, but if your new code matches behavior of old code
then *node was always NULL at entry to this function so setting it
to NULL again (which is what happens if ms_ctrl_node == NULL) should
be fine.

Maybe it's all a bit subtle though so perhaps the check is worth having.

> + *node = of_fwnode_handle(msi_ctlr_node);
> + }
> +
> + return rid;
> }
>
> /**
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 8003e3218c46..8ddb05d5c96a 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -702,7 +702,8 @@ void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
> void pci_msi_mask_irq(struct irq_data *data);
> void pci_msi_unmask_irq(struct irq_data *data);
> 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);
> +u32 pci_msi_map_rid_ctlr_node(struct irq_domain *domain, struct pci_dev *pdev,
> + struct fwnode_handle **node);
> struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
> void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> struct msi_desc *desc);
>