[PATCH 1/2] genirq: Introduce parent and children concept for IRQ

[Ning Jiang <ning.n.jiang@xxxxxxxxx>]

For chained and nested irq, there exists parent and children relation
in nature. Especially for nested irq, its handler function is executed
in the parent thread context.  If we need to resend a nested interrupt,
we have to trace all the way back to its ancestor and trigger ancestor's
irq flow handler.  If we retrigger the nested interrupt directly, we'll
get warning message in irq_nested_primary_handler(). Introduce parent
and children concept so that we can get the parent irq number in such
condition.

Signed-off-by: Ning Jiang <ning.n.jiang@xxxxxxxxx>
---
 include/linux/irq.h  |   14 ++++++++++++++
 kernel/irq/chip.c    |   16 ++++++++++++++++
 kernel/irq/irqdesc.c |    2 ++
 3 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 45593d0..e043d1a 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -146,6 +146,8 @@ struct irq_domain;
 struct irq_data {
 	unsigned int		irq;
 	unsigned long		hwirq;
+	unsigned int		parent_irq;
+	unsigned int		has_children;
 	unsigned int		node;
 	unsigned int		state_use_accessors;
 	struct irq_chip		*chip;
@@ -523,6 +525,7 @@ static inline void dynamic_irq_init(unsigned int irq)
 }
 
 /* Set/get chip/data for an IRQ: */
+extern int irq_set_parent_irq(unsigned int irq, unsigned int parent_irq);
 extern int irq_set_chip(unsigned int irq, struct irq_chip *chip);
 extern int irq_set_handler_data(unsigned int irq, void *data);
 extern int irq_set_chip_data(unsigned int irq, void *data);
@@ -530,6 +533,17 @@ extern int irq_set_irq_type(unsigned int irq, unsigned int type);
 extern int irq_set_msi_desc(unsigned int irq, struct msi_desc *entry);
 extern struct irq_data *irq_get_irq_data(unsigned int irq);
 
+static inline unsigned int irq_get_parent_irq(unsigned int irq)
+{
+	struct irq_data *d = irq_get_irq_data(irq);
+	return d ? d->parent_irq : NO_IRQ;
+}
+
+static inline unsigned int irq_data_get_parent_irq(struct irq_data *d)
+{
+	return d->parent_irq;
+}
+
 static inline struct irq_chip *irq_get_chip(unsigned int irq)
 {
 	struct irq_data *d = irq_get_irq_data(irq);
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 6cec1a2..a382fef 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -20,6 +20,22 @@
 
 #include "internals.h"
 
+int irq_set_parent_irq(unsigned int irq, unsigned int parent_irq)
+{
+	unsigned long flags, flags_parent;
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
+	struct irq_desc *desc_parent = irq_get_desc_lock(parent_irq, &flags_parent, 0);
+
+	if (!desc || !desc_parent || (parent_irq == NO_IRQ))
+		return -EINVAL;
+	desc->irq_data.parent_irq = parent_irq;
+	desc_parent->irq_data.has_children = true;
+	irq_put_desc_unlock(desc_parent, flags_parent);
+	irq_put_desc_unlock(desc, flags);
+	return 0;
+}
+EXPORT_SYMBOL(irq_set_parent_irq);
+
 /**
  *	irq_set_chip - set the irq chip for an irq
  *	@irq:	irq number
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 192a302..bf60ba9 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -76,6 +76,8 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
 	int cpu;
 
 	desc->irq_data.irq = irq;
+	desc->irq_data.parent_irq = NO_IRQ;
+	desc->irq_data.has_children = false;
 	desc->irq_data.chip = &no_irq_chip;
 	desc->irq_data.chip_data = NULL;
 	desc->irq_data.handler_data = NULL;
-- 
1.7.1

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