driver core: platform: Introduce platform_get_mem_or_io()

There are at least few existing users of the proposed API which
retrieves either MEM or IO resource from platform device.

Make it common to utilize in the existing and new users.

Cc: Eric Auger <eric.auger@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: Peng Hao <peng.hao2@zte.com.cn>
Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20201209203642.27648-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/platform.c

@@ -63,6 +63,21 @@ struct resource *platform_get_resource(struct platform_device *dev,
 }
 EXPORT_SYMBOL_GPL(platform_get_resource);
 
+struct resource *platform_get_mem_or_io(struct platform_device *dev,
+					unsigned int num)
+{
+	u32 i;
+
+	for (i = 0; i < dev->num_resources; i++) {
+		struct resource *r = &dev->resource[i];
+
+		if ((resource_type(r) & (IORESOURCE_MEM|IORESOURCE_IO)) && num-- == 0)
+			return r;
+	}
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(platform_get_mem_or_io);
+
 #ifdef CONFIG_HAS_IOMEM
 /**
  * devm_platform_get_and_ioremap_resource - call devm_ioremap_resource() for a

include/linux/platform_device.h

@@ -52,6 +52,9 @@ extern struct device platform_bus;
 
 extern struct resource *platform_get_resource(struct platform_device *,
 					      unsigned int, unsigned int);
+extern struct resource *platform_get_mem_or_io(struct platform_device *,
+					       unsigned int);
+
 extern struct device *
 platform_find_device_by_driver(struct device *start,
 			       const struct device_driver *drv);