net: core: add of_find_net_device_by_node()

Add a helper function which allows getting the struct net_device pointer
associated with a given struct device_node pointer. This is useful for
instance for DSA Ethernet devices not backed by a platform_device, but a PCI
device.

Since we need to access net_class which is not accessible outside of
net/core/net-sysfs.c, this helper function is also added here and gated
with CONFIG_OF_NET.

Network devices initialized with SET_NETDEV_DEV() are also taken into
account by checking for dev->parent first and then falling back to
checking the device pointer within struct net_device.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/of_net.h

@@ -9,8 +9,11 @@
 
 #ifdef CONFIG_OF_NET
 #include <linux/of.h>
+
+struct net_device;
 extern int of_get_phy_mode(struct device_node *np);
 extern const void *of_get_mac_address(struct device_node *np);
+extern struct net_device *of_find_net_device_by_node(struct device_node *np);
 #else
 static inline int of_get_phy_mode(struct device_node *np)
 {
@@ -21,6 +24,11 @@ static inline const void *of_get_mac_address(struct device_node *np)
 {
 	return NULL;
 }
+
+static inline struct net_device *of_find_net_device_by_node(struct device_node *np)
+{
+	return NULL;
+}
 #endif
 
 #endif /* __LINUX_OF_NET_H */

net/core/net-sysfs.c

@@ -23,6 +23,7 @@
 #include <linux/export.h>
 #include <linux/jiffies.h>
 #include <linux/pm_runtime.h>
+#include <linux/of.h>
 
 #include "net-sysfs.h"
 
@@ -1374,6 +1375,30 @@ static struct class net_class = {
 	.namespace = net_namespace,
 };
 
+#ifdef CONFIG_OF_NET
+static int of_dev_node_match(struct device *dev, const void *data)
+{
+	int ret = 0;
+
+	if (dev->parent)
+		ret = dev->parent->of_node == data;
+
+	return ret == 0 ? dev->of_node == data : ret;
+}
+
+struct net_device *of_find_net_device_by_node(struct device_node *np)
+{
+	struct device *dev;
+
+	dev = class_find_device(&net_class, NULL, np, of_dev_node_match);
+	if (!dev)
+		return NULL;
+
+	return to_net_dev(dev);
+}
+EXPORT_SYMBOL(of_find_net_device_by_node);
+#endif
+
 /* Delete sysfs entries but hold kobject reference until after all
  * netdev references are gone.
  */