driver core: platform: Introduce platform_get_irq_optional()

In some cases the interrupt line of a device is optional. Introduce a
new platform_get_irq_optional() that works much like platform_get_irq()
but does not output an error on failure to find the interrupt.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20190828083411.2496-1-thierry.reding@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/platform.c

@@ -192,6 +192,28 @@ int platform_get_irq(struct platform_device *dev, unsigned int num)
 }
 EXPORT_SYMBOL_GPL(platform_get_irq);
 
+/**
+ * platform_get_irq_optional - get an optional IRQ for a device
+ * @dev: platform device
+ * @num: IRQ number index
+ *
+ * Gets an IRQ for a platform device. Device drivers should check the return
+ * value for errors so as to not pass a negative integer value to the
+ * request_irq() APIs. This is the same as platform_get_irq(), except that it
+ * does not print an error message if an IRQ can not be obtained.
+ *
+ * Example:
+ *		int irq = platform_get_irq_optional(pdev, 0);
+ *		if (irq < 0)
+ *			return irq;
+ *
+ * Return: IRQ number on success, negative error number on failure.
+ */
+int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
+{
+	return __platform_get_irq(dev, num);
+}
+
 /**
  * platform_irq_count - Count the number of IRQs a platform device uses
  * @dev: platform device

include/linux/platform_device.h

@@ -58,6 +58,7 @@ extern void __iomem *
 devm_platform_ioremap_resource(struct platform_device *pdev,
 			       unsigned int index);
 extern int platform_get_irq(struct platform_device *, unsigned int);
+extern int platform_get_irq_optional(struct platform_device *, unsigned int);
 extern int platform_irq_count(struct platform_device *);
 extern struct resource *platform_get_resource_byname(struct platform_device *,
 						     unsigned int,