[PATCH 3/5] genirq: Introduce two helper functions

[Shanker Donthineni <sdonthineni@nvidia.com>]

Introduce helper functions irq_find_free_area() and irq_find_next_irq().
The first function is used to locate available free space for a new IRQ,
and the second one is used to find the next valid IRQ.

These helper functions will be later modified to utilize the Maple data
structure in a later patch. Additionally, in order to align the moving
to the new data structure, the IRQ_BITMAP_BITS is renamed to
MAX_SPARSE_IRQS.

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
---
 kernel/irq/internals.h |  4 ++--
 kernel/irq/irqdesc.c   | 28 +++++++++++++++++++---------
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 2fd17057ed4b..5d741b0e7d5e 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -12,9 +12,9 @@
 #include <linux/sched/clock.h>
 
 #ifdef CONFIG_SPARSE_IRQ
-# define IRQ_BITMAP_BITS	(NR_IRQS + 8196)
+# define MAX_SPARSE_IRQS	(NR_IRQS + 8196)
 #else
-# define IRQ_BITMAP_BITS	NR_IRQS
+# define MAX_SPARSE_IRQS	NR_IRQS
 #endif
 
 #define istate core_internal_state__do_not_mess_with_it
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index a4911f7ebb07..aacfb4826c5e 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -131,7 +131,18 @@ int nr_irqs = NR_IRQS;
 EXPORT_SYMBOL_GPL(nr_irqs);
 
 static DEFINE_MUTEX(sparse_irq_lock);
-static DECLARE_BITMAP(allocated_irqs, IRQ_BITMAP_BITS);
+static DECLARE_BITMAP(allocated_irqs, MAX_SPARSE_IRQS);
+
+static int irq_find_free_area(unsigned int from, unsigned int cnt)
+{
+	return bitmap_find_next_zero_area(allocated_irqs, MAX_SPARSE_IRQS,
+					  from, cnt, 0);
+}
+
+static unsigned int irq_find_next_irq(unsigned int offset)
+{
+	return find_next_bit(allocated_irqs, nr_irqs, offset);
+}
 
 #ifdef CONFIG_SPARSE_IRQ
 
@@ -519,7 +530,7 @@ static int alloc_descs(unsigned int start, unsigned int cnt, int node,
 
 static int irq_expand_nr_irqs(unsigned int nr)
 {
-	if (nr > IRQ_BITMAP_BITS)
+	if (nr > MAX_SPARSE_IRQS)
 		return -ENOMEM;
 	nr_irqs = nr;
 	return 0;
@@ -537,11 +548,11 @@ int __init early_irq_init(void)
 	printk(KERN_INFO "NR_IRQS: %d, nr_irqs: %d, preallocated irqs: %d\n",
 	       NR_IRQS, nr_irqs, initcnt);
 
-	if (WARN_ON(nr_irqs > IRQ_BITMAP_BITS))
-		nr_irqs = IRQ_BITMAP_BITS;
+	if (WARN_ON(nr_irqs > MAX_SPARSE_IRQS))
+		nr_irqs = MAX_SPARSE_IRQS;
 
-	if (WARN_ON(initcnt > IRQ_BITMAP_BITS))
-		initcnt = IRQ_BITMAP_BITS;
+	if (WARN_ON(initcnt > MAX_SPARSE_IRQS))
+		initcnt = MAX_SPARSE_IRQS;
 
 	if (initcnt > nr_irqs)
 		nr_irqs = initcnt;
@@ -813,8 +824,7 @@ __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,
 
 	mutex_lock(&sparse_irq_lock);
 
-	start = bitmap_find_next_zero_area(allocated_irqs, IRQ_BITMAP_BITS,
-					   from, cnt, 0);
+	start = irq_find_free_area(from, cnt);
 	ret = -EEXIST;
 	if (irq >=0 && start != irq)
 		goto unlock;
@@ -839,7 +849,7 @@ EXPORT_SYMBOL_GPL(__irq_alloc_descs);
  */
 unsigned int irq_get_next_irq(unsigned int offset)
 {
-	return find_next_bit(allocated_irqs, nr_irqs, offset);
+	return irq_find_next_irq(offset);
 }
 
 struct irq_desc *
-- 
2.25.1