[netdevice] Add the concept of a network upper-layer driver

Add the concept of a network upper-layer driver, which can create
arbitrary devices on top of network devices.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/netdevice.h

 /** Declare a network-layer protocol */
 #define __net_protocol __table_entry ( NET_PROTOCOLS, 01 )
 
+/** A network upper-layer driver */
+struct net_driver {
+	/** Name */
+	const char *name;
+	/** Probe device
+	 *
+	 * @v netdev		Network device
+	 * @ret rc		Return status code
+	 */
+	int ( * probe ) ( struct net_device *netdev );
+	/** Notify of device or link state change
+	 *
+	 * @v netdev		Network device
+	 */
+	void ( * notify ) ( struct net_device *netdev );
+	/** Remove device
+	 *
+	 * @v netdev		Network device
+	 */
+	void ( * remove ) ( struct net_device *netdev );
+};
+
+/** Network driver table */
+#define NET_DRIVERS __table ( struct net_driver, "net_drivers" )
+
+/** Declare a network driver */
+#define __net_driver __table_entry ( NET_DRIVERS, 01 )
+
 extern struct list_head net_devices;
 extern struct net_device_operations null_netdev_operations;
 extern struct settings_operations netdev_settings_operations;
 	netdev->settings.settings.op = &netdev_settings_operations;
 }
 
-/**
- * Mark network device as having link up
- *
- * @v netdev		Network device
- */
-static inline __attribute__ (( always_inline )) void
-netdev_link_up ( struct net_device *netdev ) {
-	netdev->link_rc = 0;
-}
-
-/**
- * Mark network device as having link down due to a specific error
- *
- * @v netdev		Network device
- * @v rc		Link status code
- */
-static inline __attribute__ (( always_inline )) void
-netdev_link_err ( struct net_device *netdev, int rc ) {
-	netdev->link_rc = rc;
-}
-
 /**
  * Check link state of network device
  *
 	return ( netdev->state & NETDEV_IRQ_ENABLED );
 }
 
+extern void netdev_link_err ( struct net_device *netdev, int rc );
 extern void netdev_link_down ( struct net_device *netdev );
 extern int netdev_tx ( struct net_device *netdev, struct io_buffer *iobuf );
 extern void netdev_tx_complete_err ( struct net_device *netdev,
 	netdev_tx_complete_next_err ( netdev, 0 );
 }
 
+/**
+ * Mark network device as having link up
+ *
+ * @v netdev		Network device
+ */
+static inline __attribute__ (( always_inline )) void
+netdev_link_up ( struct net_device *netdev ) {
+	netdev_link_err ( netdev, 0 );
+}
+
 #endif /* _IPXE_NETDEVICE_H */

src/net/netdevice.c

 	__einfo_errortab ( EINFO_EUNKNOWN_LINK_STATUS ),
 };
 
+/**
+ * Notify drivers of network device or link state change
+ *
+ * @v netdev		Network device
+ */
+static void netdev_notify ( struct net_device *netdev ) {
+	struct net_driver *driver;
+
+	for_each_table_entry ( driver, NET_DRIVERS )
+		driver->notify ( netdev );
+}
+
+/**
+ * Mark network device as having a specific link state
+ *
+ * @v netdev		Network device
+ * @v rc		Link status code
+ */
+void netdev_link_err ( struct net_device *netdev, int rc ) {
+
+	/* Record link state */
+	netdev->link_rc = rc;
+	if ( netdev->link_rc == 0 ) {
+		DBGC ( netdev, "NETDEV %p link is up\n", netdev );
+	} else {
+		DBGC ( netdev, "NETDEV %p link is down: %s\n",
+		       netdev, strerror ( netdev->link_rc ) );
+	}
+
+	/* Notify drivers of link state change */
+	netdev_notify ( netdev );
+}
+
 /**
  * Mark network device as having link down
  *
 	 */
 	if ( ( netdev->link_rc == 0 ) ||
 	     ( netdev->link_rc == -EUNKNOWN_LINK_STATUS ) ) {
-		netdev->link_rc = -ENOTCONN;
+		netdev_link_err ( netdev, -ENOTCONN );
 	}
 }
 
  */
 int register_netdev ( struct net_device *netdev ) {
 	static unsigned int ifindex = 0;
+	struct net_driver *driver;
 	int rc;
 
 	/* Create device name */
 	/* Set initial link-layer address */
 	netdev->ll_protocol->init_addr ( netdev->hw_addr, netdev->ll_addr );
 
+	/* Add to device list */
+	netdev_get ( netdev );
+	list_add_tail ( &netdev->list, &net_devices );
+	DBGC ( netdev, "NETDEV %p registered as %s (phys %s hwaddr %s)\n",
+	       netdev, netdev->name, netdev->dev->name,
+	       netdev_addr ( netdev ) );
+
 	/* Register per-netdev configuration settings */
 	if ( ( rc = register_settings ( netdev_settings ( netdev ),
 					NULL ) ) != 0 ) {
 		DBGC ( netdev, "NETDEV %p could not register settings: %s\n",
 		       netdev, strerror ( rc ) );
-		return rc;
+		goto err_register_settings;
 	}
 
-	/* Add to device list */
-	netdev_get ( netdev );
-	list_add_tail ( &netdev->list, &net_devices );
-	DBGC ( netdev, "NETDEV %p registered as %s (phys %s hwaddr %s)\n",
-	       netdev, netdev->name, netdev->dev->name,
-	       netdev_addr ( netdev ) );
+	/* Probe device */
+	for_each_table_entry ( driver, NET_DRIVERS ) {
+		if ( ( rc = driver->probe ( netdev ) ) != 0 ) {
+			DBGC ( netdev, "NETDEV %p could not add %s device: "
+			       "%s\n", netdev, driver->name, strerror ( rc ) );
+			goto err_probe;
+		}
+	}
 
 	return 0;
+
+ err_probe:
+	for_each_table_entry_continue_reverse ( driver, NET_DRIVERS )
+		driver->remove ( netdev );
+	unregister_settings ( netdev_settings ( netdev ) );
+ err_register_settings:
+	return rc;
 }
 
 /**
 	/* Add to head of open devices list */
 	list_add ( &netdev->open_list, &open_net_devices );
 
+	/* Notify drivers of device state change */
+	netdev_notify ( netdev );
+
 	return 0;
 }
 
 
 	DBGC ( netdev, "NETDEV %p closing\n", netdev );
 
+	/* Remove from open devices list */
+	list_del ( &netdev->open_list );
+
+	/* Mark as closed */
+	netdev->state &= ~NETDEV_OPEN;
+
+	/* Notify drivers of device state change */
+	netdev_notify ( netdev );
+
 	/* Close the device */
 	netdev->op->close ( netdev );
 
 	/* Flush TX and RX queues */
 	netdev_tx_flush ( netdev );
 	netdev_rx_flush ( netdev );
-
-	/* Mark as closed */
-	netdev->state &= ~NETDEV_OPEN;
-
-	/* Remove from open devices list */
-	list_del ( &netdev->open_list );
 }
 
 /**
  * Removes the network device from the list of network devices.
  */
 void unregister_netdev ( struct net_device *netdev ) {
+	struct net_driver *driver;
 
 	/* Ensure device is closed */
 	netdev_close ( netdev );
 
+	/* Remove device */
+	for_each_table_entry_reverse ( driver, NET_DRIVERS )
+		driver->remove ( netdev );
+
 	/* Unregister per-netdev configuration settings */
 	unregister_settings ( netdev_settings ( netdev ) );