PCI/irq: Add pci_request_irq() and pci_free_irq() helpers

These are small wrappers around request_threaded_irq() and free_irq(),
which dynamically allocate space for the device name so that drivers don't
need to keep static buffers for these around. Additionally it works with
device-relative vector numbers to make the usage easier, and force the
IRQF_SHARED flag on given that it has no runtime overhead and should be
supported by all PCI devices.

Signed-off-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>
Reviewed-by: Thomas Gleixner <[e-mail]>

drivers/pci/irq.c

···
 /*
- * PCI IRQ failure handing code
+ * PCI IRQ handling code
  *
  * Copyright (c) 2008 James Bottomley <[e-mail]>
+ * Copyright (C) 2017 Christoph Hellwig.
  */
 
 #include <linux/acpi.h>
···
 	return PCI_LOST_IRQ_NO_INFORMATION;
 }
 EXPORT_SYMBOL(pci_lost_interrupt);
+
+/**
+ * pci_request_irq - allocate an interrupt line for a PCI device
+ * @dev:	PCI device to operate on
+ * @nr:		device-relative interrupt vector index (0-based).
+ * @handler:	Function to be called when the IRQ occurs.
+ *		Primary handler for threaded interrupts.
+ *		If NULL and thread_fn != NULL the default primary handler is
+ *		installed.
+ * @thread_fn:	Function called from the IRQ handler thread
+ *		If NULL, no IRQ thread is created
+ * @dev_id:	Cookie passed back to the handler function
+ * @fmt:	Printf-like format string naming the handler
+ *
+ * This call allocates interrupt resources and enables the interrupt line and
+ * IRQ handling. From the point this call is made @handler and @thread_fn may
+ * be invoked.  All interrupts requested using this function might be shared.
+ *
+ * @dev_id must not be NULL and must be globally unique.
+ */
+int pci_request_irq(struct pci_dev *dev, unsigned int nr, irq_handler_t handler,
+		irq_handler_t thread_fn, void *dev_id, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+	char *devname;
+
+	va_start(ap, fmt);
+	devname = kvasprintf(GFP_KERNEL, fmt, ap);
+	va_end(ap);
+
+	ret = request_threaded_irq(pci_irq_vector(dev, nr), handler, thread_fn,
+			IRQF_SHARED, devname, dev_id);
+	if (ret)
+		kfree(devname);
+	return ret;
+}
+EXPORT_SYMBOL(pci_request_irq);
+
+/**
+ * pci_free_irq - free an interrupt allocated with pci_request_irq
+ * @dev:	PCI device to operate on
+ * @nr:		device-relative interrupt vector index (0-based).
+ * @dev_id:	Device identity to free
+ *
+ * Remove an interrupt handler. The handler is removed and if the interrupt
+ * line is no longer in use by any driver it is disabled.  The caller must
+ * ensure the interrupt is disabled on the device before calling this function.
+ * The function does not return until any executing interrupts for this IRQ
+ * have completed.
+ *
+ * This function must not be called from interrupt context.
+ */
+void pci_free_irq(struct pci_dev *dev, unsigned int nr, void *dev_id)
+{
+	kfree(free_irq(pci_irq_vector(dev, nr), dev_id));
+}
+EXPORT_SYMBOL(pci_free_irq);

include/linux/pci.h

···
 #include <linux/kobject.h>
 #include <linux/atomic.h>
 #include <linux/device.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/resource_ext.h>
 #include <uapi/linux/pci.h>
···
 int pci_select_bars(struct pci_dev *dev, unsigned long flags);
 bool pci_device_is_present(struct pci_dev *pdev);
 void pci_ignore_hotplug(struct pci_dev *dev);
+
+int __printf(6, 7) pci_request_irq(struct pci_dev *dev, unsigned int nr,
+		irq_handler_t handler, irq_handler_t thread_fn, void *dev_id,
+		const char *fmt, ...);
+void pci_free_irq(struct pci_dev *dev, unsigned int nr, void *dev_id);
 
 /* ROM control related routines */
 int pci_enable_rom(struct pci_dev *pdev);