PCI: Add msi_controller setup_irqs() method for special multivector setup

Add a msi_controller setup_irqs() method so MSI chip providers can
implement their own multivector MSI setup.

[bhelgaas: changelog]
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pratyush Anand <pratyush.anand@gmail.com>

drivers/pci/msi.c

@@ -105,9 +105,12 @@ void __weak arch_teardown_msi_irq(unsigned int irq)
 
 int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 {
+	struct msi_controller *chip = dev->bus->msi;
 	struct msi_desc *entry;
 	int ret;
 
+	if (chip && chip->setup_irqs)
+		return chip->setup_irqs(chip, dev, nvec, type);
 	/*
 	 * If an architecture wants to support multiple MSI, it needs to
 	 * override arch_setup_msi_irqs()

include/linux/msi.h

@@ -163,6 +163,8 @@ struct msi_controller {
 
 	int (*setup_irq)(struct msi_controller *chip, struct pci_dev *dev,
 			 struct msi_desc *desc);
+	int (*setup_irqs)(struct msi_controller *chip, struct pci_dev *dev,
+			  int nvec, int type);
 	void (*teardown_irq)(struct msi_controller *chip, unsigned int irq);
 };