diff --git a/drivers/irqchip/irq-versatile-fpga.c b/drivers/irqchip/irq-versatile-fpga.c
index 065b7a31a47833a3cbe444f3e8779611ca2ede3a..47a52ab580d863ba2266d26f228befc2695218f1 100644
--- a/drivers/irqchip/irq-versatile-fpga.c
+++ b/drivers/irqchip/irq-versatile-fpga.c
@@ -119,7 +119,7 @@ static int fpga_irqdomain_map(struct irq_domain *d, unsigned int irq,
 
 	/* Skip invalid IRQs, only register handlers for the real ones */
 	if (!(f->valid & BIT(hwirq)))
-		return -ENOTSUPP;
+		return -EPERM;
 	irq_set_chip_data(irq, f);
 	irq_set_chip_and_handler(irq, &f->chip,
 				handle_level_irq);
diff --git a/drivers/irqchip/irq-vic.c b/drivers/irqchip/irq-vic.c
index 884d11c7355fb5d5cc0636c25b06e1ba1b856ef5..2bbb00404cf5001df2c6f8654de6d467d58f3b6d 100644
--- a/drivers/irqchip/irq-vic.c
+++ b/drivers/irqchip/irq-vic.c
@@ -197,7 +197,7 @@ static int vic_irqdomain_map(struct irq_domain *d, unsigned int irq,
 
 	/* Skip invalid IRQs, only register handlers for the real ones */
 	if (!(v->valid_sources & (1 << hwirq)))
-		return -ENOTSUPP;
+		return -EPERM;
 	irq_set_chip_and_handler(irq, &vic_chip, handle_level_irq);
 	irq_set_chip_data(irq, v->base);
 	set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 5a83dde8ca0c22544cead99b7ea3e2e0be813d27..54a4d5223238e15843559d16386bc4cdc1e63f25 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -143,7 +143,10 @@ static unsigned int irq_domain_legacy_revmap(struct irq_domain *domain,
  * irq_domain_add_simple() - Allocate and register a simple irq_domain.
  * @of_node: pointer to interrupt controller's device tree node.
  * @size: total number of irqs in mapping
- * @first_irq: first number of irq block assigned to the domain
+ * @first_irq: first number of irq block assigned to the domain,
+ *	pass zero to assign irqs on-the-fly. This will result in a
+ *	linear IRQ domain so it is important to use irq_create_mapping()
+ *	for each used IRQ, especially when SPARSE_IRQ is enabled.
  * @ops: map/unmap domain callbacks
  * @host_data: Controller private data pointer
  *
@@ -191,6 +194,7 @@ struct irq_domain *irq_domain_add_simple(struct device_node *of_node,
 	/* A linear domain is the default */
 	return irq_domain_add_linear(of_node, size, ops, host_data);
 }
+EXPORT_SYMBOL_GPL(irq_domain_add_simple);
 
 /**
  * irq_domain_add_legacy() - Allocate and register a legacy revmap irq_domain.
@@ -397,11 +401,12 @@ static void irq_domain_disassociate_many(struct irq_domain *domain,
 	while (count--) {
 		int irq = irq_base + count;
 		struct irq_data *irq_data = irq_get_irq_data(irq);
-		irq_hw_number_t hwirq = irq_data->hwirq;
+		irq_hw_number_t hwirq;
 
 		if (WARN_ON(!irq_data || irq_data->domain != domain))
 			continue;
 
+		hwirq = irq_data->hwirq;
 		irq_set_status_flags(irq, IRQ_NOREQUEST);
 
 		/* remove chip and handler */