1 files changed, 40 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/prom_parse.c b/arch/powerpc/kernel/prom_parse.c
index 12c51e4ad2b4..ea6fd552c7ea 100644
--- a/arch/powerpc/kernel/prom_parse.c
+++ b/arch/powerpc/kernel/prom_parse.c
@@ -5,6 +5,7 @@
 #include <linux/pci_regs.h>
 #include <linux/module.h>
 #include <linux/ioport.h>
+#include <linux/etherdevice.h>
 #include <asm/prom.h>
 #include <asm/pci-bridge.h>
 
@@ -1003,3 +1004,42 @@ int of_irq_map_one(struct device_node *device, int index, struct of_irq *out_irq
         return res;
 }
 EXPORT_SYMBOL_GPL(of_irq_map_one);
+
+/**
+ * Search the device tree for the best MAC address to use.  'mac-address' is
+ * checked first, because that is supposed to contain to "most recent" MAC
+ * address. If that isn't set, then 'local-mac-address' is checked next,
+ * because that is the default address.  If that isn't set, then the obsolete
+ * 'address' is checked, just in case we're using an old device tree.
+ *
+ * Note that the 'address' property is supposed to contain a virtual address of
+ * the register set, but some DTS files have redefined that property to be the
+ * MAC address.
+ *
+ * All-zero MAC addresses are rejected, because those could be properties that
+ * exist in the device tree, but were not set by U-Boot.  For example, the
+ * DTS could define 'mac-address' and 'local-mac-address', with zero MAC
+ * addresses.  Some older U-Boots only initialized 'local-mac-address'.  In
+ * this case, the real MAC is in 'local-mac-address', and 'mac-address' exists
+ * but is all zeros.
+*/
+const void *of_get_mac_address(struct device_node *np)
+{
+        struct property *pp;
+
+        pp = of_find_property(np, "mac-address", NULL);
+        if (pp && (pp->length == 6) && is_valid_ether_addr(pp->value))
+                return pp->value;
+
+        pp = of_find_property(np, "local-mac-address", NULL);
+        if (pp && (pp->length == 6) && is_valid_ether_addr(pp->value))
+                return pp->value;
+
+        pp = of_find_property(np, "address", NULL);
+        if (pp && (pp->length == 6) && is_valid_ether_addr(pp->value))
+                return pp->value;
+
+        return NULL;
+}
+EXPORT_SYMBOL(of_get_mac_address);
+