[PATCH v6 1/5] PCI/MSI: Export pci_msix_prepare_desc() for dynamic MSI-X allocations

Shradha Gupta
2025-06-11T14:10:03Z

For supporting dynamic MSI-X vector allocation by PCI controllers, enabling
the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN is not enough, msix_prepare_msi_desc()
to prepare the MSI descriptor is also needed.

Export pci_msix_prepare_desc() to allow PCI controllers to support dynamic
MSI-X vector allocation.

Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
drivers/pci/msi/irqdomain.c | 5 +++--
include/linux/msi.h | 2 ++
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
index c05152733993..765312c92d9b 100644
--- a/drivers/pci/msi/irqdomain.c
+++ b/drivers/pci/msi/irqdomain.c
@@ -222,13 +222,14 @@ static void pci_irq_unmask_msix(struct irq_data *data)
pci_msix_unmask(irq_data_get_msi_desc(data));
}

-static void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
- struct msi_desc *desc)
+void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
+ struct msi_desc *desc)
{
/* Don't fiddle with preallocated MSI descriptors */
if (!desc->pci.mask_base)
msix_prepare_msi_desc(to_pci_dev(desc->dev), desc);
}
+EXPORT_SYMBOL_GPL(pci_msix_prepare_desc);

static const struct msi_domain_template pci_msix_template = {
.chip = {
diff --git a/include/linux/msi.h b/include/linux/msi.h
index 6863540f4b71..7f254bde5426 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -706,6 +706,8 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
struct irq_domain *parent);
u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
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);
#else /* CONFIG_PCI_MSI */
static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
{
--
2.34.1