From: John Crispin <blogic@openwrt.org>
Date: Sun, 27 Jul 2014 09:40:01 +0100
Subject: NET: add of_get_mac_address_mtd()

Many embedded devices have information such as mac addresses stored inside mtd
devices. This patch allows us to add a property inside a node describing a
network interface. The new property points at a mtd partition with an offset
where the mac address can be found.

Signed-off-by: John Crispin <blogic@openwrt.org>
---
 drivers/of/of_net.c    |   37 +++++++++++++++++++++++++++++++++++++
 include/linux/of_net.h |    1 +
 2 files changed, 38 insertions(+)

--- a/drivers/of/of_net.c
+++ b/drivers/of/of_net.c
@@ -10,6 +10,7 @@
 #include <linux/of_net.h>
 #include <linux/phy.h>
 #include <linux/export.h>
+#include <linux/mtd/mtd.h>
 
 /**
  * of_get_phy_mode - Get phy mode for given device_node
@@ -80,3 +81,45 @@ const void *of_get_mac_address(struct de
 	return of_get_mac_addr(np, "address");
 }
 EXPORT_SYMBOL(of_get_mac_address);
+
+#ifdef CONFIG_MTD
+int of_get_mac_address_mtd(struct device_node *np, unsigned char *mac)
+{
+	struct device_node *mtd_np = NULL;
+	size_t retlen;
+	int size, ret;
+	struct mtd_info *mtd;
+	const char *part;
+	const __be32 *list;
+	phandle phandle;
+	u32 mac_inc = 0;
+
+	list = of_get_property(np, "mtd-mac-address", &size);
+	if (!list || (size != (2 * sizeof(*list))))
+		return -ENOENT;
+
+	phandle = be32_to_cpup(list++);
+	if (phandle)
+		mtd_np = of_find_node_by_phandle(phandle);
+
+	if (!mtd_np)
+		return -ENOENT;
+
+	part = of_get_property(mtd_np, "label", NULL);
+	if (!part)
+		part = mtd_np->name;
+
+	mtd = get_mtd_device_nm(part);
+	if (IS_ERR(mtd))
+		return PTR_ERR(mtd);
+
+	ret = mtd_read(mtd, be32_to_cpup(list), 6, &retlen, mac);
+	put_mtd_device(mtd);
+
+	if (!of_property_read_u32(np, "mtd-mac-address-increment", &mac_inc))
+		mac[5] += mac_inc;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_get_mac_address_mtd);
+#endif
--- a/include/linux/of_net.h
+++ b/include/linux/of_net.h
@@ -13,6 +13,14 @@
 struct net_device;
 extern int of_get_phy_mode(struct device_node *np);
 extern const void *of_get_mac_address(struct device_node *np);
+#ifdef CONFIG_MTD
+extern int of_get_mac_address_mtd(struct device_node *np, unsigned char *mac);
+#else
+static inline int of_get_mac_address_mtd(struct device_node *np, unsigned char *mac)
+{
+	return -ENOENT;
+}
+#endif
 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)