net: allow setting env enetaddr from net device setting

If the net driver has setup a valid ethernet address and an ethernet
address is not set in the environment already, then set the environment
variables from the net driver setting.

This enables pxe booting on boards which don't set ethaddr env variable.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>

doc/README.enetaddr

@@ -32,7 +32,11 @@ Correct flow of setting up the MAC address (summarized):
 
 1. Read from hardware in initialize() function
 2. Read from environment in net/eth.c after initialize()
-3. Give priority to the value in the environment if a conflict
+3. The environment variable will be compared to the driver initialized
+   struct eth_device->enetaddr. If they differ, a warning is printed, and the
+   environment variable will be used unchanged.
+   If the environment variable is not set, it will be initialized from
+   eth_device->enetaddr, and a warning will be printed.
 4. Program the address into hardware if the following conditions are met:
 	a) The relevant driver has a 'write_addr' function
 	b) The user hasn't set an 'ethmacskip' environment variable

net/eth.c

@@ -62,6 +62,15 @@ int eth_getenv_enetaddr_by_index(const char *base_name, int index,
 	return eth_getenv_enetaddr(enetvar, enetaddr);
 }
 
+int eth_setenv_enetaddr_by_index(const char *base_name, int index,
+				 uchar *enetaddr)
+{
+	char enetvar[32];
+	sprintf(enetvar, index ? "%s%daddr" : "%saddr", base_name, index);
+	return eth_setenv_enetaddr(enetvar, enetaddr);
+}
+
+
 static int eth_mac_skip(int index)
 {
 	char enetvar[15];
@@ -205,6 +214,11 @@ int eth_write_hwaddr(struct eth_device *dev, const char *base_name,
 		}
 
 		memcpy(dev->enetaddr, env_enetaddr, 6);
+	} else if (is_valid_ether_addr(dev->enetaddr)) {
+		eth_setenv_enetaddr_by_index(base_name, eth_number,
+					     dev->enetaddr);
+		printf("\nWarning: %s using MAC address from net device\n",
+			dev->name);
 	}
 
 	if (dev->write_hwaddr &&