[tip: irq/msi] genirq/msi: Provide interface to retrieve Linux interrupt number

["tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>]

The following commit has been merged into the irq/msi branch of tip:

Commit-ID:     cf15f43acaad31dabb2646cef170a506a1d663eb
Gitweb:        https://git.kernel.org/tip/cf15f43acaad31dabb2646cef170a506a1d663eb
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Fri, 10 Dec 2021 23:19:23 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 16 Dec 2021 22:16:40 +01:00

genirq/msi: Provide interface to retrieve Linux interrupt number

This allows drivers to retrieve the Linux interrupt number instead of
fiddling with MSI descriptors.

msi_get_virq() returns the Linux interrupt number or 0 in case that there
is no entry for the given MSI index.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20211210221814.780824745@linutronix.de

---
 include/linux/msi.h |  2 ++
 kernel/irq/msi.c    | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index d206239..7593fc3 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -153,6 +153,8 @@ struct msi_device_data {
 
 int msi_setup_device_data(struct device *dev);
 
+unsigned int msi_get_virq(struct device *dev, unsigned int index);
+
 /* Helpers to hide struct msi_desc implementation details */
 #define msi_desc_to_dev(desc)		((desc)->dev)
 #define dev_to_msi_list(dev)		(&(dev)->msi_list)
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 8e433f1..ab5e83f 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -105,6 +105,42 @@ int msi_setup_device_data(struct device *dev)
 	return 0;
 }
 
+/**
+ * msi_get_virq - Return Linux interrupt number of a MSI interrupt
+ * @dev:	Device to operate on
+ * @index:	MSI interrupt index to look for (0-based)
+ *
+ * Return: The Linux interrupt number on success (> 0), 0 if not found
+ */
+unsigned int msi_get_virq(struct device *dev, unsigned int index)
+{
+	struct msi_desc *desc;
+	bool pcimsi;
+
+	if (!dev->msi.data)
+		return 0;
+
+	pcimsi = dev_is_pci(dev) ? to_pci_dev(dev)->msi_enabled : false;
+
+	for_each_msi_entry(desc, dev) {
+		/* PCI-MSI has only one descriptor for multiple interrupts. */
+		if (pcimsi) {
+			if (desc->irq && index < desc->nvec_used)
+				return desc->irq + index;
+			break;
+		}
+
+		/*
+		 * PCI-MSIX and platform MSI use a descriptor per
+		 * interrupt.
+		 */
+		if (desc->msi_index == index)
+			return desc->irq;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(msi_get_virq);
+
 #ifdef CONFIG_SYSFS
 static ssize_t msi_mode_show(struct device *dev, struct device_attribute *attr,
 			     char *buf)