eth: platform: add a helper for loading netdev->dev_addr

Commit 406f42fa ("net-next: When a bond have a massive amount
of VLANs...") introduced a rbtree for faster Ethernet address look
up. To maintain netdev->dev_addr in this tree we need to make all
the writes to it got through appropriate helpers.

There is a handful of drivers which pass netdev->dev_addr as
the destination buffer to eth_platform_get_mac_address().
Add a helper which takes a dev pointer instead, so it can call
an appropriate helper.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/etherdevice.h

@@ -29,6 +29,7 @@ struct device;
 struct fwnode_handle;
 
 int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr);
+int platform_get_ethdev_address(struct device *dev, struct net_device *netdev);
 unsigned char *arch_get_platform_mac_address(void);
 int nvmem_get_mac_address(struct device *dev, void *addrbuf);
 int device_get_mac_address(struct device *dev, char *addr);

net/ethernet/eth.c

@@ -523,6 +523,26 @@ int eth_platform_get_mac_address(struct device *dev, u8 *mac_addr)
 }
 EXPORT_SYMBOL(eth_platform_get_mac_address);
 
+/**
+ * platform_get_ethdev_address - Set netdev's MAC address from a given device
+ * @dev:	Pointer to the device
+ * @netdev:	Pointer to netdev to write the address to
+ *
+ * Wrapper around eth_platform_get_mac_address() which writes the address
+ * directly to netdev->dev_addr.
+ */
+int platform_get_ethdev_address(struct device *dev, struct net_device *netdev)
+{
+	u8 addr[ETH_ALEN] __aligned(2);
+	int ret;
+
+	ret = eth_platform_get_mac_address(dev, addr);
+	if (!ret)
+		eth_hw_addr_set(netdev, addr);
+	return ret;
+}
+EXPORT_SYMBOL(platform_get_ethdev_address);
+
 /**
  * nvmem_get_mac_address - Obtain the MAC address from an nvmem cell named
  * 'mac-address' associated with given device.