[PATCH v3 1/3] net: cdc_ncm: add get/set ethernet address functions

[Charles Hyde <chip.programmer@gmail.com>]

This patch adds support for pushing a MAC address out to USB based
ethernet controllers driven by cdc_ncm.  With this change, ifconfig can
now set the device's MAC address.  For example, the Dell Universal Dock
D6000 is driven by cdc_ncm.  The D6000 can now have its MAC address set
by ifconfig, as it can be done in Windows.  This was tested with a D6000
using ifconfig on an x86 based chromebook, where iproute2 is not
available.

Signed-off-by: Charles Hyde <charles.hyde@dellteam.com>
Cc: Mario Limonciello <mario.limonciello@dell.com>
Cc: chip.programmer@gmail.com
Cc: Oliver Neukum <oliver@neukum.org>
Cc: linux-usb@vger.kernel.org
---
 drivers/net/usb/cdc_ncm.c | 74 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 73 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 50c05d0f44cb..85093579612f 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -750,6 +750,78 @@ int cdc_ncm_change_mtu(struct net_device *net, int new_mtu)
 }
 EXPORT_SYMBOL_GPL(cdc_ncm_change_mtu);
 
+/* Provide method to get MAC address from the USB device's ethernet controller.
+ * If the device supports CDC_GET_ADDRESS, we should receive just six bytes.
+ * Otherwise, use the prior method by asking for the descriptor.
+ */
+static int cdc_ncm_get_ethernet_address(struct usbnet *dev,
+					struct cdc_ncm_ctx *ctx)
+{
+	int ret;
+	char *buf;
+
+	buf = kmalloc(ETH_ALEN, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = usbnet_read_cmd(dev, USB_CDC_GET_NET_ADDRESS,
+			      USB_DIR_IN | USB_TYPE_CLASS
+			      | USB_RECIP_INTERFACE, 0,
+			      USB_REQ_SET_ADDRESS, buf, ETH_ALEN);
+	if (ret == ETH_ALEN) {
+		memcpy(dev->net->dev_addr, buf, ETH_ALEN);
+		ret = 0;	/* success */
+	} else {
+		ret = usbnet_get_ethernet_addr(dev,
+					       ctx->ether_desc->iMACAddress);
+	}
+	kfree(buf);
+	return ret;
+}
+
+/* Provide method to push MAC address to the USB device's ethernet controller.
+ * If the device does not support CDC_SET_ADDRESS, there is no harm and we
+ * proceed as before.
+ */
+static int cdc_ncm_set_ethernet_address(struct usbnet *dev,
+					struct sockaddr *addr)
+{
+	int ret;
+	char *buf;
+
+	buf = kmalloc(ETH_ALEN, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	memcpy(buf, addr->sa_data, ETH_ALEN);
+	ret = usbnet_write_cmd(dev, USB_CDC_SET_NET_ADDRESS,
+			       USB_DIR_OUT | USB_TYPE_CLASS
+			       | USB_RECIP_INTERFACE, 0,
+			       USB_REQ_SET_ADDRESS, buf, ETH_ALEN);
+	if (ret == ETH_ALEN)
+		ret = 0;	/* success */
+	else if (ret < 0)
+		dev_dbg(&dev->udev->dev, "bad MAC address put, %d\n", ret);
+
+	kfree(buf);
+	return ret;
+}
+
+/* Provide method to push MAC address to the USB device's ethernet controller.
+ */
+int cdc_ncm_set_mac_addr(struct net_device *net, void *p)
+{
+	struct usbnet *dev = netdev_priv(net);
+
+	/* Try to push the MAC address out to the device.  Ignore any errors,
+	 * to be compatible with prior versions of this source.
+	 */
+	cdc_ncm_set_ethernet_address(dev, (struct sockaddr *)p);
+
+	return eth_mac_addr(net, p);
+}
+EXPORT_SYMBOL_GPL(cdc_ncm_set_mac_addr);
+
 static const struct net_device_ops cdc_ncm_netdev_ops = {
 	.ndo_open	     = usbnet_open,
 	.ndo_stop	     = usbnet_stop,
@@ -757,7 +829,7 @@ static const struct net_device_ops cdc_ncm_netdev_ops = {
 	.ndo_tx_timeout	     = usbnet_tx_timeout,
 	.ndo_get_stats64     = usbnet_get_stats64,
 	.ndo_change_mtu	     = cdc_ncm_change_mtu,
-	.ndo_set_mac_address = eth_mac_addr,
+	.ndo_set_mac_address = cdc_ncm_set_mac_addr,
 	.ndo_validate_addr   = eth_validate_addr,
 };
 
-- 
2.20.1