[PATCHv6 04/13] irqdomain: add irq_alloc_mapping() function

[Thomas Petazzoni]

This commit extends the irqdomain subsystem with an
irq_alloc_mapping() function which allows to let the irqdomain code
find an available hwirq number in the range [ 0 ; domain size ] for
the given domain, and create a virq mapping for it.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Acked-by: Grant Likely <grant.likely at linaro.org>
---
 include/linux/irqdomain.h |  2 ++
 kernel/irq/irqdomain.c    | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index c983ed1..1ffa336 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -195,6 +195,8 @@ static inline unsigned int irq_linear_revmap(struct irq_domain *domain,
 extern unsigned int irq_find_mapping(struct irq_domain *host,
 				     irq_hw_number_t hwirq);
 extern unsigned int irq_create_direct_mapping(struct irq_domain *host);
+extern unsigned int irq_alloc_mapping(struct irq_domain *host,
+				      irq_hw_number_t *hwirq);
 extern int irq_create_strict_mappings(struct irq_domain *domain,
 				      unsigned int irq_base,
 				      irq_hw_number_t hwirq_base, int count);
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 706724e..034bbac 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -375,6 +375,42 @@ unsigned int irq_create_direct_mapping(struct irq_domain *domain)
 EXPORT_SYMBOL_GPL(irq_create_direct_mapping);
 
 /**
+ * irq_alloc_mapping() - Allocate an irq for mapping
+ * @domain: domain to allocate the irq for or NULL for default domain
+ * @hwirq:  reference to the returned hwirq
+ *
+ * This routine are used for irq controllers which can choose the
+ * hardware interrupt number from a range [ 0 ; domain size ], such as
+ * is often the case with PCI MSI controllers. The function will
+ * returned the allocated hwirq number in the hwirq pointer, and the
+ * corresponding virq number as the return value.
+ */
+unsigned int irq_alloc_mapping(struct irq_domain *domain,
+			       irq_hw_number_t *out_hwirq)
+{
+	irq_hw_number_t hwirq;
+	int rc;
+
+	pr_debug("irq_alloc_mapping(0x%p)\n", domain);
+
+	for (hwirq = 0; hwirq < domain->revmap_size; hwirq++)
+		if (domain->linear_revmap[hwirq] == 0)
+			break;
+
+	if (hwirq == domain->hwirq_max) {
+		pr_debug("-> no available hwirq found\n");
+		return 0;
+	}
+
+	rc = irq_create_mapping(domain, hwirq);
+	if (rc)
+		*out_hwirq = hwirq;
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(irq_alloc_mapping);
+
+/**
  * irq_create_mapping() - Map a hardware interrupt into linux irq space
  * @domain: domain owning this hardware interrupt or NULL for default domain
  * @hwirq: hardware irq number in that domain space
-- 
1.8.1.2