irqdomain: Make __irq_domain_create() return an error code

__irq_domain_create() can fail for several reasons. When it fails it
returns a NULL pointer and so filters out the exact failure reason.
The only user of __irq_domain_create() is irq_domain_instantiate() which
can return a PTR_ERR value. On __irq_domain_create() failure, it uses an
arbitrary error code.

Rather than using this arbitrary error value, make __irq_domain_create()
return is own error code and use that one.

[ tglx: Remove the pointless ERR_CAST. domain is a valid return pointer ]

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240614173232.1184015-11-herve.codina@bootlin.com

Author: hcodina

kernel/irq/irqdomain.c

@@ -187,17 +187,17 @@ static struct irq_domain *__irq_domain_create(const struct irq_domain_info *info
 	if (WARN_ON((info->size && info->direct_max) ||
 		    (!IS_ENABLED(CONFIG_IRQ_DOMAIN_NOMAP) && info->direct_max) ||
 		    (info->direct_max && info->direct_max != info->hwirq_max)))
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	domain = kzalloc_node(struct_size(domain, revmap, info->size),
 			      GFP_KERNEL, of_node_to_nid(to_of_node(info->fwnode)));
 	if (!domain)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	err = irq_domain_set_name(domain, info->fwnode);
 	if (err) {
 		kfree(domain);
-		return NULL;
+		return ERR_PTR(err);
 	}
 
 	domain->fwnode = fwnode_handle_get(info->fwnode);
@@ -260,8 +260,8 @@ struct irq_domain *irq_domain_instantiate(const struct irq_domain_info *info)
 	struct irq_domain *domain;
 
 	domain = __irq_domain_create(info);
-	if (!domain)
-		return ERR_PTR(-ENOMEM);
+	if (IS_ERR(domain))
+		return domain;
 
 	domain->flags |= info->domain_flags;