#include <linux/module.h>
#include <linux/platform_device.h>

static int parent_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct platform_device *middle;

	dev_info(dev, "probe\n");

	middle = platform_device_register_data(dev, "middle", PLATFORM_DEVID_AUTO, NULL, 0);
	if (IS_ERR(middle))
		return dev_err_probe(dev, PTR_ERR(middle), "failed to create middle\n");

	return 0;
}

static int middle_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct platform_device *child;
	struct device_link *link;

	dev_info(dev, "probe\n");

	child = platform_device_register_data(dev, "child", PLATFORM_DEVID_AUTO, NULL, 0);
	if (IS_ERR(child))
		return dev_err_probe(dev, PTR_ERR(child), "failed to create child\n");

	dev_info(dev, "device_link_add\n");

	/*
	 * Note how the device link is created between the parent device and the
	 * child device. This is equivalent to what happens in the phy-core
	 * because ci_hdrc calls phy_get(dev->parent, "usb-phy");
	 */
	link = device_link_add(dev->parent, &child->dev, DL_FLAG_STATELESS);
	if (link)
		dev_err(dev, "Creating circular device link should have failed!\n");
	else
		dev_info(dev, "Creating device link failed (as it should)\n");

	return 0;
}

static int child_probe(struct platform_device *pdev)
{
	dev_info(&pdev->dev, "probe\n");
	return 0;
}

static struct platform_driver parent_driver = {
	.probe	= parent_probe,
	.driver	= {
		.name = "parent",
	},
};

static struct platform_driver middle_driver = {
	.probe	= middle_probe,
	.driver	= {
		.name = "middle",
	},
};

static struct platform_driver child_driver = {
	.probe	= child_probe,
	.driver	= {
		.name = "child",
	},
};

static int __init circdl_init(void)
{
	platform_driver_register(&parent_driver);
	platform_driver_register(&middle_driver);
	platform_driver_register(&child_driver);
	platform_device_register_simple("parent", PLATFORM_DEVID_AUTO, NULL, 0);
	return 0;
}

module_init(circdl_init)
MODULE_LICENSE("GPL v2");