genirq/irqdomain: Add irq_domain_update_bus_token helper

We can have irq domains that are identified by the same fwnode
(because they are serviced by the same HW), and yet have different
functionnality (because they serve different busses, for example).
This is what we use the bus_token field.

Since we don't use this field when generating the domain name,
all the aliasing domains will get the same name, and the debugfs
file creation fails. Also, bus_token is updated by individual drivers,
and the core code is unaware of that update.

In order to sort this mess, let's introduce a helper that takes care
of updating bus_token, and regenerate the debugfs file.

A separate patch will update all the individual users.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irqdomain.h

@@ -273,6 +273,9 @@ static inline bool is_fwnode_irqchip(struct fwnode_handle *fwnode)
 	return fwnode && fwnode->type == FWNODE_IRQCHIP;
 }
 
+extern void irq_domain_update_bus_token(struct irq_domain *domain,
+					enum irq_domain_bus_token bus_token);
+
 static inline
 struct irq_domain *irq_find_matching_fwnode(struct fwnode_handle *fwnode,
 					    enum irq_domain_bus_token bus_token)

kernel/irq/irqdomain.c

@@ -245,6 +245,37 @@ void irq_domain_remove(struct irq_domain *domain)
 }
 EXPORT_SYMBOL_GPL(irq_domain_remove);
 
+void irq_domain_update_bus_token(struct irq_domain *domain,
+				 enum irq_domain_bus_token bus_token)
+{
+	char *name;
+
+	if (domain->bus_token == bus_token)
+		return;
+
+	mutex_lock(&irq_domain_mutex);
+
+	domain->bus_token = bus_token;
+
+	name = kasprintf(GFP_KERNEL, "%s-%d", domain->name, bus_token);
+	if (!name) {
+		mutex_unlock(&irq_domain_mutex);
+		return;
+	}
+
+	debugfs_remove_domain_dir(domain);
+
+	if (domain->flags & IRQ_DOMAIN_NAME_ALLOCATED)
+		kfree(domain->name);
+	else
+		domain->flags |= IRQ_DOMAIN_NAME_ALLOCATED;
+
+	domain->name = name;
+	debugfs_add_domain_dir(domain);
+
+	mutex_unlock(&irq_domain_mutex);
+}
+
 /**
  * irq_domain_add_simple() - Register an irq_domain and optionally map a range of irqs
  * @of_node: pointer to interrupt controller's device tree node.