[PATCH net-next 2/3] net: ethernet: add property "nvmem_macaddr_swap" to swap macaddr bytes order

[Joakim Zhang <qiangqing.zhang@xxxxxxx>]

From: Fugang Duan <fugang.duan@xxxxxxx>

ethernet controller driver call .of_get_mac_address() to get
the mac address from devictree tree, if these properties are
not present, then try to read from nvmem.

For example, read MAC address from nvmem:
of_get_mac_address()
	of_get_mac_addr_nvmem()
		nvmem_get_mac_address()

i.MX6x/7D/8MQ/8MM platforms ethernet MAC address read from
nvmem ocotp eFuses, but it requires to swap the six bytes
order.

The patch add optional property "nvmem_macaddr_swap" to swap
macaddr bytes order.

Signed-off-by: Fugang Duan <fugang.duan@xxxxxxx>
Signed-off-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
---
 net/ethernet/eth.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 4106373180c6..11057671a9d6 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -534,8 +534,10 @@ EXPORT_SYMBOL(eth_platform_get_mac_address);
 int nvmem_get_mac_address(struct device *dev, void *addrbuf)
 {
 	struct nvmem_cell *cell;
-	const void *mac;
+	const unsigned char *mac;
+	unsigned char macaddr[ETH_ALEN];
 	size_t len;
+	int i = 0;
 
 	cell = nvmem_cell_get(dev, "mac-address");
 	if (IS_ERR(cell))
@@ -547,14 +549,27 @@ int nvmem_get_mac_address(struct device *dev, void *addrbuf)
 	if (IS_ERR(mac))
 		return PTR_ERR(mac);
 
-	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
-		kfree(mac);
-		return -EINVAL;
+	if (len != ETH_ALEN)
+		goto invalid_addr;
+
+	if (dev->of_node &&
+	    of_property_read_bool(dev->of_node, "nvmem_macaddr_swap")) {
+		for (i = 0; i < ETH_ALEN; i++)
+			macaddr[i] = mac[ETH_ALEN - i - 1];
+	} else {
+		ether_addr_copy(macaddr, mac);
 	}
 
-	ether_addr_copy(addrbuf, mac);
+	if (!is_valid_ether_addr(macaddr))
+		goto invalid_addr;
+
+	ether_addr_copy(addrbuf, macaddr);
 	kfree(mac);
 
 	return 0;
+
+invalid_addr:
+	kfree(mac);
+	return -EINVAL;
 }
 EXPORT_SYMBOL(nvmem_get_mac_address);
-- 
2.17.1