[v3 PATCH 4/6] usb: roles: add API to get usb_role_switch by node

[Chunfeng Yun]

Add fwnode_usb_role_switch_get() to make easier to get
usb_role_switch by fwnode which register it.
It's useful when there is not device_connection registered
between two drivers and only knows the fwnode which register
usb_role_switch.

Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
---
v3 changes:
  1. use fwnodes instead of node suggested by Andy
  2. rebuild the API suggested by Heikki

v2 no changes
---
 drivers/usb/roles/class.c | 31 +++++++++++++++++++++++++++++++
 include/linux/usb/role.h  |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
index f45d8df5cfb8..5ecb57f8960b 100644
--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -12,6 +12,7 @@
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 #include <linux/slab.h>
 
 static struct class *role_class;
@@ -135,6 +136,36 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(usb_role_switch_get);
 
+static int __switch_match_fwnode(struct device *dev, const void *fwnode)
+{
+	return dev_fwnode(dev->parent) == (const struct fwnode_handle *)fwnode;
+}
+
+/**
+ * fwnode_usb_role_switch_get - Find USB role switch by it's parent fwnode
+ * @fwnode: The fwnode that register USB role switch
+ *
+ * Finds and returns role switch registered by @fwnode. The reference count
+ * for the found switch is incremented.
+ */
+struct usb_role_switch *
+fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
+{
+	struct usb_role_switch *sw;
+	struct device *dev;
+
+	dev = class_find_device(role_class, NULL, fwnode,
+				__switch_match_fwnode);
+	if (!dev)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	sw = to_role_switch(dev);
+	WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
+
+	return sw;
+}
+EXPORT_SYMBOL_GPL(fwnode_usb_role_switch_get);
+
 /**
  * usb_role_switch_put - Release handle to a switch
  * @sw: USB Role Switch
diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
index c05ffa6abda9..d21cd55d9e45 100644
--- a/include/linux/usb/role.h
+++ b/include/linux/usb/role.h
@@ -46,6 +46,8 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role);
 enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw);
 struct usb_role_switch *usb_role_switch_get(struct device *dev);
 void usb_role_switch_put(struct usb_role_switch *sw);
+struct usb_role_switch *
+fwnode_usb_role_switch_get(struct fwnode_handle *fwnode);
 
 struct usb_role_switch *
 usb_role_switch_register(struct device *parent,
-- 
2.20.1