wwan_hwsim: support network interface creation

Add support for networking interface creation via the WWAN core by
registering the WWAN netdev creation ops for each simulated WWAN device.
Implemented minimalistic netdev support where the xmit callback just
consumes all egress skbs.

This should help with WWAN network interfaces creation testing.
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wwan/wwan_hwsim.c

@@ -14,10 +14,13 @@
 #include <linux/spinlock.h>
 #include <linux/list.h>
 #include <linux/skbuff.h>
+#include <linux/netdevice.h>
 #include <linux/wwan.h>
 #include <linux/debugfs.h>
 #include <linux/workqueue.h>
 
+#include <net/arp.h>
+
 static int wwan_hwsim_devsnum = 2;
 module_param_named(devices, wwan_hwsim_devsnum, int, 0444);
 MODULE_PARM_DESC(devices, "Number of simulated devices");
@@ -64,6 +67,38 @@ static const struct file_operations wwan_hwsim_debugfs_devdestroy_fops;
 static void wwan_hwsim_port_del_work(struct work_struct *work);
 static void wwan_hwsim_dev_del_work(struct work_struct *work);
 
+static netdev_tx_t wwan_hwsim_netdev_xmit(struct sk_buff *skb,
+					  struct net_device *ndev)
+{
+	ndev->stats.tx_packets++;
+	ndev->stats.tx_bytes += skb->len;
+	consume_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+static const struct net_device_ops wwan_hwsim_netdev_ops = {
+	.ndo_start_xmit = wwan_hwsim_netdev_xmit,
+};
+
+static void wwan_hwsim_netdev_setup(struct net_device *ndev)
+{
+	ndev->netdev_ops = &wwan_hwsim_netdev_ops;
+	ndev->needs_free_netdev = true;
+
+	ndev->mtu = ETH_DATA_LEN;
+	ndev->min_mtu = ETH_MIN_MTU;
+	ndev->max_mtu = ETH_MAX_MTU;
+
+	ndev->type = ARPHRD_NONE;
+	ndev->flags = IFF_POINTOPOINT | IFF_NOARP;
+}
+
+static const struct wwan_ops wwan_hwsim_wwan_rtnl_ops = {
+	.owner = THIS_MODULE,
+	.priv_size = 0,			/* No private data */
+	.setup = wwan_hwsim_netdev_setup,
+};
+
 static int wwan_hwsim_port_start(struct wwan_port *wport)
 {
 	struct wwan_hwsim_port *port = wwan_port_get_drvdata(wport);
@@ -254,6 +289,10 @@ static struct wwan_hwsim_dev *wwan_hwsim_dev_new(void)
 
 	INIT_WORK(&dev->del_work, wwan_hwsim_dev_del_work);
 
+	err = wwan_register_ops(&dev->dev, &wwan_hwsim_wwan_rtnl_ops, dev);
+	if (err)
+		goto err_unreg_dev;
+
 	dev->debugfs_topdir = debugfs_create_dir(dev_name(&dev->dev),
 						 wwan_hwsim_debugfs_topdir);
 	debugfs_create_file("destroy", 0200, dev->debugfs_topdir, dev,
@@ -265,6 +304,12 @@ static struct wwan_hwsim_dev *wwan_hwsim_dev_new(void)
 
 	return dev;
 
+err_unreg_dev:
+	device_unregister(&dev->dev);
+	/* Memory will be freed in the device release callback */
+
+	return ERR_PTR(err);
+
 err_free_dev:
 	kfree(dev);
 
@@ -290,6 +335,9 @@ static void wwan_hwsim_dev_del(struct wwan_hwsim_dev *dev)
 
 	debugfs_remove(dev->debugfs_topdir);
 
+	/* This will remove all child netdev(s) */
+	wwan_unregister_ops(&dev->dev);
+
 	/* Make sure that there is no pending deletion work */
 	if (current_work() != &dev->del_work)
 		cancel_work_sync(&dev->del_work);