genirq/irq_sim: Return the base of the irq range from irq_sim_init()

Returning the base of the allocated interrupt range from irq_sim_init() and
devm_irq_sim_init() allows users to handle the logic of associating irq
numbers with any other driver-specific resources without having to use
irq_sim_irqnum().

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20180304121018.640-4-brgl@bgdev.pl

kernel/irq/irq_sim.c

@@ -50,7 +50,8 @@ static void irq_sim_handle_irq(struct irq_work *work)
  * @sim:        The interrupt simulator object to initialize.
  * @num_irqs:   Number of interrupts to allocate
  *
- * Returns 0 on success and a negative error number on failure.
+ * On success: return the base of the allocated interrupt range.
+ * On failure: a negative errno.
  */
 int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
 {
@@ -79,7 +80,7 @@ int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
 	init_irq_work(&sim->work_ctx.work, irq_sim_handle_irq);
 	sim->irq_count = num_irqs;
 
-	return 0;
+	return sim->irq_base;
 }
 EXPORT_SYMBOL_GPL(irq_sim_init);
 
@@ -111,7 +112,8 @@ static void devm_irq_sim_release(struct device *dev, void *res)
  * @sim:        The interrupt simulator object to initialize.
  * @num_irqs:   Number of interrupts to allocate
  *
- * Returns 0 on success and a negative error number on failure.
+ * On success: return the base of the allocated interrupt range.
+ * On failure: a negative errno.
  */
 int devm_irq_sim_init(struct device *dev, struct irq_sim *sim,
 		      unsigned int num_irqs)
@@ -132,7 +134,7 @@ int devm_irq_sim_init(struct device *dev, struct irq_sim *sim,
 	dr->sim = sim;
 	devres_add(dev, dr);
 
-	return 0;
+	return rv;
 }
 EXPORT_SYMBOL_GPL(devm_irq_sim_init);