driver core: platform: Make platform_get_irq_optional() optional

Currently the platform_get_irq_optional() returns an error code even
if IRQ resource sumply has not been found. It prevents caller to be
error code agnostic in their error handling.

Now:
	ret = platform_get_irq_optional(...);
	if (ret != -ENXIO)
		return ret; // respect deferred probe
	if (ret > 0)
		...we get an IRQ...

After proposed change:
	ret = platform_get_irq_optional(...);
	if (ret < 0)
		return ret;
	if (ret > 0)
		...we get an IRQ...

Reported-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210331144526.19439-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/platform.c

@@ -168,25 +168,7 @@ devm_platform_ioremap_resource_byname(struct platform_device *pdev,
 EXPORT_SYMBOL_GPL(devm_platform_ioremap_resource_byname);
 #endif /* CONFIG_HAS_IOMEM */
 
-/**
- * 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.
- *
- * For example::
- *
- *		int irq = platform_get_irq_optional(pdev, 0);
- *		if (irq < 0)
- *			return irq;
- *
- * Return: non-zero IRQ number on success, negative error number on failure.
- */
-int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
+static int platform_do_get_irq(struct platform_device *dev, unsigned int num)
 {
 	int ret;
 #ifdef CONFIG_SPARC
@@ -254,6 +236,37 @@ int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
 	WARN(ret == 0, "0 is an invalid IRQ number\n");
 	return ret;
 }
+
+/**
+ * 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 and returns
+ * 0 when IRQ resource has not been found.
+ *
+ * For example::
+ *
+ *		int irq = platform_get_irq_optional(pdev, 0);
+ *		if (irq < 0)
+ *			return irq;
+ *		if (irq > 0)
+ *			...we have IRQ line defined...
+ *
+ * Return: non-zero IRQ number on success, negative error number on failure.
+ */
+int platform_get_irq_optional(struct platform_device *dev, unsigned int num)
+{
+	int ret;
+
+	ret = platform_do_get_irq(dev, num);
+	if (ret == -ENXIO)
+		return 0;
+	return ret;
+}
 EXPORT_SYMBOL_GPL(platform_get_irq_optional);
 
 /**
@@ -277,7 +290,7 @@ int platform_get_irq(struct platform_device *dev, unsigned int num)
 {
 	int ret;
 
-	ret = platform_get_irq_optional(dev, num);
+	ret = platform_do_get_irq(dev, num);
 	if (ret < 0 && ret != -EPROBE_DEFER)
 		dev_err(&dev->dev, "IRQ index %u not found\n", num);
 
@@ -295,7 +308,7 @@ int platform_irq_count(struct platform_device *dev)
 {
 	int ret, nr = 0;
 
-	while ((ret = platform_get_irq_optional(dev, nr)) >= 0)
+	while ((ret = platform_do_get_irq(dev, nr)) >= 0)
 		nr++;
 
 	if (ret == -EPROBE_DEFER)