网络设备之注册
注册网络设备时，会调用pci_driver->probe函数，以e100网卡驱动为例，在调用alloc_ehterdev分配内存之后，会接着调用register_netdev进行设备注册，注册过程包含部分成员初始化，注册到文件系统，消息通知等；
1 /** 2 * 设备注册函数调用关系图 3 * e100_probe 4 * |-->alloc_etherdev-->alloc_netdev_mqs 5 * |-->register_netdev-->register_netdevice 6 */
下面对register_netdevice函数进行分析：
1 /** 2 * register_netdevice - register a network device 3 * @dev: device to register 4 * 5 * Take a completed network device structure and add it to the kernel 6 * interfaces. A %NETDEV_REGISTER message is sent to the netdev notifier 7 * chain. 0 is returned on success. A negative errno code is returned 8 * on a failure to set up the device, or if the name is a duplicate. 9 * 10 * Callers must hold the rtnl semaphore. You may want 11 * register_netdev() instead of this. 12 * 13 * BUGS: 14 * The locking appears insufficient to guarantee two parallel registers 15 * will not get the same name. 16 */ 17 18 int register_netdevice(struct net_device *dev) 19 { 20 int ret; 21 struct net *net = dev_net(dev); 22 23 BUG_ON(dev_boot_phase); 24 ASSERT_RTNL(); 25 26 might_sleep(); 27 28 /* When net_device's are persistent, this will be fatal. */ 29 BUG_ON(dev->reg_state != NETREG_UNINITIALIZED); 30 BUG_ON(!net); 31 32 spin_lock_init(&dev->addr_list_lock); 33 netdev_set_addr_lockdep_class(dev); 34 35 /* 获取可用设备名 */ 36 ret = dev_get_valid_name(net, dev, dev->name); 37 if (ret < 0) 38 goto out; 39 40 /* Init, if this function is available */ 41 /* 调用设备的初始化函数 */ 42 if (dev->netdev_ops->ndo_init) { 43 ret = dev->netdev_ops->ndo_init(dev); 44 if (ret) { 45 if (ret > 0) 46 ret = -EIO; 47 goto out; 48 } 49 } 50 51 /* vlan数据包接收过滤 */ 52 if (((dev->hw_features | dev->features) & 53 NETIF_F_HW_VLAN_CTAG_FILTER) && 54 /* vlan注册/销毁函数不存在 */ 55 (!dev->netdev_ops->ndo_vlan_rx_add_vid || 56 !dev->netdev_ops->ndo_vlan_rx_kill_vid)) { 57 netdev_WARN(dev, "Buggy VLAN acceleration in driver!\n"); 58 ret = -EINVAL; 59 goto err_uninit; 60 } 61 62 ret = -EBUSY; 63 /* 设备索引不存在，则分配一个 */ 64 if (!dev->ifindex) 65 dev->ifindex = dev_new_index(net); 66 /* 索引存在，则进行测试 */ 67 else if (__dev_get_by_index(net, dev->ifindex)) 68 goto err_uninit; 69 70 /* Transfer changeable features to wanted_features and enable 71 * software offloads (GSO and GRO). 72 */ 73 /* 设置功能标识 */ 74 dev->hw_features |= NETIF_F_SOFT_FEATURES; 75 dev->features |= NETIF_F_SOFT_FEATURES; 76 dev->wanted_features = dev->features & dev->hw_features; 77 78 if (!(dev->flags & IFF_LOOPBACK)) 79 dev->hw_features |= NETIF_F_NOCACHE_COPY; 80 81 /* If IPv4 TCP segmentation offload is supported we should also 82 * allow the device to enable segmenting the frame with the option 83 * of ignoring a static IP ID value. This doesn't enable the 84 * feature itself but allows the user to enable it later. 85 */ 86 if (dev->hw_features & NETIF_F_TSO) 87 dev->hw_features |= NETIF_F_TSO_MANGLEID; 88 if (dev->vlan_features & NETIF_F_TSO) 89 dev->vlan_features |= NETIF_F_TSO_MANGLEID; 90 if (dev->mpls_features & NETIF_F_TSO) 91 dev->mpls_features |= NETIF_F_TSO_MANGLEID; 92 if (dev->hw_enc_features & NETIF_F_TSO) 93 dev->hw_enc_features |= NETIF_F_TSO_MANGLEID; 94 95 /* Make NETIF_F_HIGHDMA inheritable to VLAN devices. 96 */ 97 dev->vlan_features |= NETIF_F_HIGHDMA; 98 99 /* Make NETIF_F_SG inheritable to tunnel devices. 100 */ 101 dev->hw_enc_features |= NETIF_F_SG | NETIF_F_GSO_PARTIAL; 102 103 /* Make NETIF_F_SG inheritable to MPLS. 104 */ 105 dev->mpls_features |= NETIF_F_SG; 106 107 /* 通知设备初始化结束 */ 108 ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev); 109 ret = notifier_to_errno(ret); 110 if (ret) 111 goto err_uninit; 112 113 /* 设备注册到虚拟文件系统 */ 114 ret = netdev_register_kobject(dev); 115 if (ret) 116 goto err_uninit; 117 118 /*设置设备注册状态*/ 119 dev->reg_state = NETREG_REGISTERED; 120 121 __netdev_update_features(dev); 122 123 /* 124 * Default initial state at registry is that the 125 * device is present. 126 */ 127 128 set_bit(__LINK_STATE_PRESENT, &dev->state); 129 130 linkwatch_init_dev(dev); 131 132 dev_init_scheduler(dev); 133 dev_hold(dev); 134 list_netdevice(dev); 135 add_device_randomness(dev->dev_addr, dev->addr_len); 136 137 /* If the device has permanent device address, driver should 138 * set dev_addr and also addr_assign_type should be set to 139 * NET_ADDR_PERM (default value). 140 */ 141 /* 永久硬件地址，则拷贝到perm_addr */ 142 if (dev->addr_assign_type == NET_ADDR_PERM) 143 memcpy(dev->perm_addr, dev->dev_addr, dev->addr_len); 144 145 /* Notify protocols, that a new device appeared. */ 146 /* 通知设备初始化完毕 */ 147 ret = call_netdevice_notifiers(NETDEV_REGISTER, dev); 148 ret = notifier_to_errno(ret); 149 /* 失败进行回滚 */ 150 if (ret) { 151 rollback_registered(dev); 152 dev->reg_state = NETREG_UNREGISTERED; 153 } 154 /* 155 * Prevent userspace races by waiting until the network 156 * device is fully setup before sending notifications. 157 */ 158 /* 发送newlink消息 */ 159 if (!dev->rtnl_link_ops || 160 dev->rtnl_link_state == RTNL_LINK_INITIALIZED) 161 rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U, GFP_KERNEL); 162 163 out: 164 return ret; 165 166 err_uninit: 167 if (dev->netdev_ops->ndo_uninit) 168 dev->netdev_ops->ndo_uninit(dev); 169 if (dev->priv_destructor) 170 dev->priv_destructor(dev); 171 goto out; 172 }
