genirq/msi: Split msi_domain_alloc_irq_at()

In preparation for providing a special allocation function for wired
interrupts which are connected to a wire to MSI bridge, split the inner
workings of msi_domain_alloc_irq_at() out into a helper function so the
code can be shared.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240127161753.114685-9-apatel@ventanamicro.com

Author: KAGA-KOKO

kernel/irq/msi.c

@@ -1446,52 +1446,27 @@ int msi_domain_alloc_irqs_all_locked(struct device *dev, unsigned int domid, int
 	return msi_domain_alloc_locked(dev, &ctrl);
 }
 
-/**
- * msi_domain_alloc_irq_at - Allocate an interrupt from a MSI interrupt domain at
- *			     a given index - or at the next free index
- *
- * @dev:	Pointer to device struct of the device for which the interrupts
- *		are allocated
- * @domid:	Id of the interrupt domain to operate on
- * @index:	Index for allocation. If @index == %MSI_ANY_INDEX the allocation
- *		uses the next free index.
- * @affdesc:	Optional pointer to an interrupt affinity descriptor structure
- * @icookie:	Optional pointer to a domain specific per instance cookie. If
- *		non-NULL the content of the cookie is stored in msi_desc::data.
- *		Must be NULL for MSI-X allocations
- *
- * This requires a MSI interrupt domain which lets the core code manage the
- * MSI descriptors.
- *
- * Return: struct msi_map
- *
- *	On success msi_map::index contains the allocated index number and
- *	msi_map::virq the corresponding Linux interrupt number
- *
- *	On failure msi_map::index contains the error code and msi_map::virq
- *	is %0.
- */
-struct msi_map msi_domain_alloc_irq_at(struct device *dev, unsigned int domid, unsigned int index,
-				       const struct irq_affinity_desc *affdesc,
-				       union msi_instance_cookie *icookie)
+static struct msi_map __msi_domain_alloc_irq_at(struct device *dev, unsigned int domid,
+						unsigned int index,
+						const struct irq_affinity_desc *affdesc,
+						union msi_instance_cookie *icookie)
 {
 	struct msi_ctrl ctrl = { .domid	= domid, .nirqs = 1, };
 	struct irq_domain *domain;
 	struct msi_map map = { };
 	struct msi_desc *desc;
 	int ret;
 
-	msi_lock_descs(dev);
 	domain = msi_get_device_domain(dev, domid);
 	if (!domain) {
 		map.index = -ENODEV;
-		goto unlock;
+		return map;
 	}
 
 	desc = msi_alloc_desc(dev, 1, affdesc);
 	if (!desc) {
 		map.index = -ENOMEM;
-		goto unlock;
+		return map;
 	}
 
 	if (icookie)
@@ -1500,7 +1475,7 @@ struct msi_map msi_domain_alloc_irq_at(struct device *dev, unsigned int domid, u
 	ret = msi_insert_desc(dev, desc, domid, index);
 	if (ret) {
 		map.index = ret;
-		goto unlock;
+		return map;
 	}
 
 	ctrl.first = ctrl.last = desc->msi_index;
@@ -1513,7 +1488,42 @@ struct msi_map msi_domain_alloc_irq_at(struct device *dev, unsigned int domid, u
 		map.index = desc->msi_index;
 		map.virq = desc->irq;
 	}
-unlock:
+	return map;
+}
+
+/**
+ * msi_domain_alloc_irq_at - Allocate an interrupt from a MSI interrupt domain at
+ *			     a given index - or at the next free index
+ *
+ * @dev:	Pointer to device struct of the device for which the interrupts
+ *		are allocated
+ * @domid:	Id of the interrupt domain to operate on
+ * @index:	Index for allocation. If @index == %MSI_ANY_INDEX the allocation
+ *		uses the next free index.
+ * @affdesc:	Optional pointer to an interrupt affinity descriptor structure
+ * @icookie:	Optional pointer to a domain specific per instance cookie. If
+ *		non-NULL the content of the cookie is stored in msi_desc::data.
+ *		Must be NULL for MSI-X allocations
+ *
+ * This requires a MSI interrupt domain which lets the core code manage the
+ * MSI descriptors.
+ *
+ * Return: struct msi_map
+ *
+ *	On success msi_map::index contains the allocated index number and
+ *	msi_map::virq the corresponding Linux interrupt number
+ *
+ *	On failure msi_map::index contains the error code and msi_map::virq
+ *	is %0.
+ */
+struct msi_map msi_domain_alloc_irq_at(struct device *dev, unsigned int domid, unsigned int index,
+				       const struct irq_affinity_desc *affdesc,
+				       union msi_instance_cookie *icookie)
+{
+	struct msi_map map;
+
+	msi_lock_descs(dev);
+	map = __msi_domain_alloc_irq_at(dev, domid, index, affdesc, icookie);
 	msi_unlock_descs(dev);
 	return map;
 }