genirq/msi: Add MSI allocation helper and export MSI functions

MSI functions for allocation and free can be directly used by
the device drivers without any wrapper provided by bus drivers.
So export these MSI functions.

Also, add a wrapper API to allocate MSIs providing only the
number of interrupts rather than range for simpler driver usage.

Signed-off-by: Nipun Gupta <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alex Williamson <[email protected]>

Author: nipung87

include/linux/msi.h

@@ -676,6 +676,12 @@ int platform_device_msi_init_and_alloc_irqs(struct device *dev, unsigned int nve
 void platform_device_msi_free_irqs_all(struct device *dev);
 
 bool msi_device_has_isolated_msi(struct device *dev);
+
+static inline int msi_domain_alloc_irqs(struct device *dev, unsigned int domid, int nirqs)
+{
+	return msi_domain_alloc_irqs_range(dev, domid, 0, nirqs - 1);
+}
+
 #else /* CONFIG_GENERIC_MSI_IRQ */
 static inline bool msi_device_has_isolated_msi(struct device *dev)
 {

kernel/irq/msi.c

@@ -1434,6 +1434,7 @@ int msi_domain_alloc_irqs_range(struct device *dev, unsigned int domid,
 	msi_unlock_descs(dev);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(msi_domain_alloc_irqs_range);
 
 /**
  * msi_domain_alloc_irqs_all_locked - Allocate all interrupts from a MSI interrupt domain
@@ -1680,6 +1681,7 @@ void msi_domain_free_irqs_range(struct device *dev, unsigned int domid,
 	msi_domain_free_irqs_range_locked(dev, domid, first, last);
 	msi_unlock_descs(dev);
 }
+EXPORT_SYMBOL_GPL(msi_domain_free_irqs_all);
 
 /**
  * msi_domain_free_irqs_all_locked - Free all interrupts from a MSI interrupt domain