openwrt/target/linux/brcm47xx/patches-3.14/180-generate-mac-address.patch

--- a/arch/mips/bcm47xx/sprom.c
+++ b/arch/mips/bcm47xx/sprom.c
@@ -28,6 +28,7 @@
 
 #include <bcm47xx.h>
 #include <bcm47xx_nvram.h>
+#include <linux/if_ether.h>
 
 static void create_key(const char *prefix, const char *postfix,
 		       const char *name, char *buf, int len)
@@ -631,6 +632,33 @@ static void bcm47xx_fill_sprom_path_r45(
 	}
 }
 
+static bool bcm47xx_is_valid_mac(u8 *mac)
+{
+	return mac && !(mac[0] == 0x00 && mac[1] == 0x90 && mac[2] == 0x4c);
+}
+
+static int bcm47xx_increase_mac_addr(u8 *mac, u8 num)
+{
+	u8 *oui = mac + ETH_ALEN/2 - 1;
+	u8 *p = mac + ETH_ALEN - 1;
+
+	do {
+		(*p) += num;
+		if (*p > num)
+			break;
+		p--;
+		num = 1;
+	} while (p != oui);
+
+	if (p == oui) {
+		pr_err("unable to fetch mac address\n");
+		return -ENOENT;
+	}
+	return 0;
+}
+
+static int mac_addr_used = 2;
+
 static void bcm47xx_fill_sprom_ethernet(struct ssb_sprom *sprom,
 					const char *prefix, bool fallback)
 {
@@ -648,6 +676,23 @@ static void bcm47xx_fill_sprom_ethernet(
 
 	nvram_read_macaddr(prefix, "macaddr", sprom->il0mac, fallback);
 	nvram_read_macaddr(prefix, "il0macaddr", sprom->il0mac, fallback);
+
+	/* The address prefix 00:90:4C is used by Broadcom in their initial
+	   configuration. When a mac address with the prefix 00:90:4C is used
+	   all devices from the same series are sharing the same mac address.
+	   To prevent mac address collisions we replace them with a mac address
+	   based on the base address. */
+	if (!bcm47xx_is_valid_mac(sprom->il0mac)) {
+		u8 mac[6];
+		nvram_read_macaddr(NULL, "et0macaddr", mac, false);
+		if (bcm47xx_is_valid_mac(mac)) {
+			int err = bcm47xx_increase_mac_addr(mac, mac_addr_used);
+			if (!err) {
+				memcpy(sprom->il0mac, mac, ETH_ALEN);
+				mac_addr_used++;
+			}
+		}
+	}
 }
 
 static void bcm47xx_fill_board_data(struct ssb_sprom *sprom, const char *prefix,