irqdomain: Introduce init() and exit() hooks

The current API does not allow additional initialization before the
domain is published. This can lead to a race condition between consumers
and supplier as a domain can be available for consumers before being
fully ready.

Introduce the init() hook to allow additional initialization before
plublishing the domain. Also introduce the exit() hook to revert
operations done in init() on domain removal.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240614173232.1184015-13-herve.codina@bootlin.com

include/linux/irqdomain.h

@@ -141,6 +141,7 @@ struct irq_domain_chip_generic;
  *		purposes related to the irq domain.
  * @parent:	Pointer to parent irq_domain to support hierarchy irq_domains
  * @msi_parent_ops: Pointer to MSI parent domain methods for per device domain init
+ * @exit:	Function called when the domain is destroyed
  *
  * Revmap data, used internally by the irq domain code:
  * @revmap_size:	Size of the linear map table @revmap[]
@@ -169,6 +170,7 @@ struct irq_domain {
 #ifdef CONFIG_GENERIC_MSI_IRQ
 	const struct msi_parent_ops	*msi_parent_ops;
 #endif
+	void				(*exit)(struct irq_domain *d);
 
 	/* reverse map data. The linear map gets appended to the irq_domain */
 	irq_hw_number_t			hwirq_max;
@@ -268,6 +270,10 @@ void irq_domain_free_fwnode(struct fwnode_handle *fwnode);
  * @bus_token:		Domain bus token
  * @ops:		Domain operation callbacks
  * @host_data:		Controller private data pointer
+ * @init:		Function called when the domain is created.
+ *			Allow to do some additional domain initialisation.
+ * @exit:		Function called when the domain is destroyed.
+ *			Allow to do some additional cleanup operation.
  */
 struct irq_domain_info {
 	struct fwnode_handle			*fwnode;
@@ -284,6 +290,8 @@ struct irq_domain_info {
 	 */
 	struct irq_domain			*parent;
 #endif
+	int					(*init)(struct irq_domain *d);
+	void					(*exit)(struct irq_domain *d);
 };
 
 struct irq_domain *irq_domain_instantiate(const struct irq_domain_info *info);

kernel/irq/irqdomain.c

@@ -276,12 +276,14 @@ static void irq_domain_free(struct irq_domain *domain)
 struct irq_domain *irq_domain_instantiate(const struct irq_domain_info *info)
 {
 	struct irq_domain *domain;
+	int err;
 
 	domain = __irq_domain_create(info);
 	if (IS_ERR(domain))
 		return domain;
 
 	domain->flags |= info->domain_flags;
+	domain->exit = info->exit;
 
 #ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
 	if (info->parent) {
@@ -290,9 +292,19 @@ struct irq_domain *irq_domain_instantiate(const struct irq_domain_info *info)
 	}
 #endif
 
+	if (info->init) {
+		err = info->init(domain);
+		if (err)
+			goto err_domain_free;
+	}
+
 	__irq_domain_publish(domain);
 
 	return domain;
+
+err_domain_free:
+	irq_domain_free(domain);
+	return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(irq_domain_instantiate);
 
@@ -339,6 +351,9 @@ EXPORT_SYMBOL_GPL(__irq_domain_add);
  */
 void irq_domain_remove(struct irq_domain *domain)
 {
+	if (domain->exit)
+		domain->exit(domain);
+
 	mutex_lock(&irq_domain_mutex);
 	debugfs_remove_domain_dir(domain);