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

Lorenzo Pieralisi
2026-01-07T09:23:58Z

On Mon, Jan 05, 2026 at 12:21:14PM +0000, Jonathan Cameron wrote:
> 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?

Yes, I thought an explicit variable would make it clearer, don't know,
not a big deal either way I believe.

> > + 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.

As above, I thought that to help understand what the function does
assigning only if !NULL would help, you are right though.

Thanks,
Lorenzo

> > + *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);
> >
>