[PATCH v2] net: davicom: dm9000: allow to pass MAC address through mac_addr module parameter

[H. Nikolaus Schaller]

The MIPS Ingenic CI20 board is shipped with a quite old u-boot
(ci20-v2013.10 see https://elinux.org/CI20_Dev_Zone). This passes
the MAC address through dm9000.mac_addr=xx:xx:xx:xx:xx:xx
kernel module parameter to give the board a fixed MAC address.

This is not processed by the dm9000 driver which assigns a random
MAC address on each boot, making DHCP assign a new IP address
each time.

So we add a check for the mac_addr module parameter as a last
resort before assigning a random one. This mechanism can also
be used outside of u-boot to provide a value through modprobe
config.

To parse the MAC address in a new function get_mac_addr() we
use an copy adapted from the ksz884x.c driver which provides
the same functionality.

Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/davicom/dm9000.c | 42 +++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/net/ethernet/davicom/dm9000.c b/drivers/net/ethernet/davicom/dm9000.c
index 1ea3372775e6..7402030b0352 100644
--- a/drivers/net/ethernet/davicom/dm9000.c
+++ b/drivers/net/ethernet/davicom/dm9000.c
@@ -1409,6 +1409,43 @@ static struct dm9000_plat_data *dm9000_parse_dt(struct device *dev)
 	return pdata;
 }
 
+static char *mac_addr = ":";
+module_param(mac_addr, charp, 0);
+MODULE_PARM_DESC(mac_addr, "MAC address");
+
+static void get_mac_addr(struct net_device *ndev, char *macaddr)
+{
+	int i = 0;
+	int j = 0;
+	int got_num = 0;
+	int num = 0;
+
+	while (j < ETH_ALEN) {
+		if (macaddr[i]) {
+			int digit;
+
+			got_num = 1;
+			digit = hex_to_bin(macaddr[i]);
+			if (digit >= 0)
+				num = num * 16 + digit;
+			else if (':' == macaddr[i])
+				got_num = 2;
+			else
+				break;
+		} else if (got_num) {
+			got_num = 2;
+		} else {
+			break;
+		}
+		if (got_num == 2) {
+			ndev->dev_addr[j++] = (u8)num;
+			num = 0;
+			got_num = 0;
+		}
+		i++;
+	}
+}
+
 /*
  * Search DM9000 board, allocate space and register it
  */
@@ -1679,6 +1716,11 @@ dm9000_probe(struct platform_device *pdev)
 			ndev->dev_addr[i] = ior(db, i+DM9000_PAR);
 	}
 
+	if (!is_valid_ether_addr(ndev->dev_addr)) {
+		mac_src = "param";
+		get_mac_addr(ndev, mac_addr);
+	}
+
 	if (!is_valid_ether_addr(ndev->dev_addr)) {
 		inv_mac_addr = true;
 		eth_hw_addr_random(ndev);
-- 
2.23.0