網卡設備通用數據結構：
struct net_device
{
/*
* This is the first field of the "visible" part of this structure
* (i.e. as seen by users in the "Space.c" file). It is the name
* the interface.
*/
/*網絡設備名*/
char name[IFNAMSIZ];
/* device name hash chain */
/*根據網絡設備名以散列表的形式組織到dev_name_head散列表中，這樣就可以通過網絡
設備名快速地定位到網絡設備*/
struct hlist_node name_hlist;
/*
* I/O specific fields
* FIXME: Merge these and struct ifmap into one
*/
/*網絡設備共享內存的起始和終止地址*/
unsigned long mem_end; /* shared mem end */
unsigned long mem_start; /* shared mem start */
/*網絡接口I/O基地址，在探測設備時被初始化ifconfig命令可顯示和修改
當前命令*/
unsigned long base_addr; /* device I/O address */
/*分配給設備的中斷號，一般在初始化設備時被初始化*/
unsigned int irq; /* device IRQ number */
/*
* Some hardware also needs these fields, but they are not
* part of the usual set specified in Space.c.
*/
/*指定在多端口設備上使用那個端口*/
unsigned char if_port; /* Selectable AUI, TP,..*/
/*為設備分配的DMA通道*/
unsigned char dma; /* DMA channel */
/*設備狀態*/
unsigned long state;
/*網絡設備組織*/
struct net_device *next;
/*驅動程序的初始化函數*/
/* The device initialization function. Called only once. */
int (*init)(struct net_device *dev);
/* ------- Fields preinitialized in Space.c finish here ------- */
/* Net device features */
/*接口支持特性*/
unsigned long features;
#define NETIF_F_SG 1 /* Scatter/gather IO. */
#define NETIF_F_IP_CSUM 2 /* Can checksum only TCP/UDP over IPv4. */
#define NETIF_F_NO_CSUM 4 /* Does not require checksum. F.e. loopack. */
#define NETIF_F_HW_CSUM 8 /* Can checksum all the packets. */
#define NETIF_F_HIGHDMA 32 /* Can DMA to high memory. */
#define NETIF_F_FRAGLIST 64 /* Scatter/gather IO. */
#define NETIF_F_HW_VLAN_TX 128 /* Transmit VLAN hw acceleration */
#define NETIF_F_HW_VLAN_RX 256 /* Receive VLAN hw acceleration */
#define NETIF_F_HW_VLAN_FILTER 512 /* Receive filtering on VLAN */
#define NETIF_F_VLAN_CHALLENGED 1024 /* Device cannot handle VLAN packets */
#define NETIF_F_GSO 2048 /* Enable software GSO. */
#define NETIF_F_LLTX 4096 /* LockLess TX */
/* Segmentation offload features */
#define NETIF_F_GSO_SHIFT 16
#define NETIF_F_GSO_MASK 0xffff0000
#define NETIF_F_TSO (SKB_GSO_TCPV4 << NETIF_F_GSO_SHIFT)
#define NETIF_F_UFO (SKB_GSO_UDP << NETIF_F_GSO_SHIFT)
#define NETIF_F_GSO_ROBUST (SKB_GSO_DODGY << NETIF_F_GSO_SHIFT)
#define NETIF_F_TSO_ECN (SKB_GSO_TCP_ECN << NETIF_F_GSO_SHIFT)
#define NETIF_F_TSO6 (SKB_GSO_TCPV6 << NETIF_F_GSO_SHIFT)
/* List of features with software fallbacks. */
#define NETIF_F_GSO_SOFTWARE (NETIF_F_TSO | NETIF_F_TSO_ECN | NETIF_F_TSO6)
#define NETIF_F_GEN_CSUM (NETIF_F_NO_CSUM | NETIF_F_HW_CSUM)
#define NETIF_F_ALL_CSUM (NETIF_F_IP_CSUM | NETIF_F_GEN_CSUM)
/*用於連接那些已經調度有數據報輸出的網絡設備指針*/
struct net_device *next_sched;
/* Interface index. Unique device identifier */
/*網絡設備的索引號*/
int ifindex;
/*網絡設備的唯一標識，主要用於虛擬隧道設備*/
int iflink;
/*提供給應用程序獲得接口統計信息的接口*/
struct net_device_stats* (*get_stats)(struct net_device *dev);
/* List of functions to handle Wireless Extensions (instead of ioctl).
* See <net/iw_handler.h> for details. Jean II */
/*無線網相關*/
const struct iw_handler_def * wireless_handlers;
/* Instance data managed by the core of Wireless Extensions. */
struct iw_public_data * wireless_data;
const struct ethtool_ops *ethtool_ops;
/*
* This marks the end of the "visible" part of the structure. All
* fields hereafter are internal to the system, and may change at
* will (read: may be cleaned up at will).
*/
unsigned int flags; /* interface flags (a la BSD) */
/*記錄當前網絡設備IFF_PROMISC和IFF_ALLMULTI的狀態，用來配合flags的設置*/
unsigned short gflags;
unsigned short priv_flags; /* Like 'flags' but invisible to userspace. */
unsigned short padded; /* How much padding added by alloc_netdev() */
unsigned char operstate; /* RFC2863 operstate */
unsigned char link_mode; /* mapping policy to operstate */
unsigned mtu; /* interface MTU value */
unsigned short type; /* interface hardware type */
unsigned short hard_header_len; /* hardware hdr length */
struct net_device *master; /* Pointer to master device of a group,
* which this device is member of.
*/
/* Interface address info. */
/*MAC地址，通常初始化時從硬件中讀出來*/
unsigned char perm_addr[MAX_ADDR_LEN]; /* permanent hw address */
unsigned char addr_len; /* hardware address length */
unsigned short dev_id; /* for shared network cards */
struct dev_mc_list *mc_list; /* Multicast mac addresses */
int mc_count; /* Number of installed mcasts */
/*設置網絡設備混雜模式計數器*/
int promiscuity;
/*設置網絡設備接收所有組播報的計數器，每次設置或是退出操作，該字段
都會相應的加或減1，為0時，網絡設備才真正不再接收組播報*/
int allmulti;
/* Protocol specific pointers */
void *atalk_ptr; /* AppleTalk link */
void *ip_ptr; /* IPv4 specific data */
void *dn_ptr; /* DECnet specific data */
void *ip6_ptr; /* IPv6 specific data */
void *ec_ptr; /* Econet specific data */
void *ax25_ptr; /* AX.25 specific data */
/*
* Cache line mostly used on receive path (including eth_type_trans())
*/
/*該結構實例通過該字段連接到softnet_data的poll_list成員上*/
struct list_head poll_list ____cacheline_aligned_in_smp;
/* Link to poll list */
/*輪詢模式操作接口*/
int (*poll) (struct net_device *dev, int *quota);
/*讀取數據包的配額，動態變化，由netdev_budget初始化，每次從網絡設備中讀取數據包後，
會從中減去本次讀取的數據包數，當該配額等於或小於0時，結束當前輪詢等待下層輪詢
這樣即使某個網絡設備有大量的數據包輸入，也能保證其他網絡設備能及時收到數據包
在輸入時，遍歷網絡設備輪詢隊列，從選定的網絡設備中讀取數據包，一旦已經讀取的數據
包的數量操作配額，即停止本次讀取，將該網絡設備移至網絡設備輪詢隊列的隊尾，等待
下次輪詢*/
int quota;
/*數據包輸入軟中斷中，單個網絡讀取數據包的配額*/
int weight;
unsigned long last_rx; /* Time of last Rx */
/* Interface address info used in eth_type_trans() */
unsigned char dev_addr[MAX_ADDR_LEN]; /* hw address, (before bcast
because most packets are unicast) */
unsigned char broadcast[MAX_ADDR_LEN]; /* hw bcast add */
/*
* Cache line mostly used on queue transmit path (qdisc)
*/
/* device queue lock */
spinlock_t queue_lock ____cacheline_aligned_in_smp;
/*當前使用的根排隊規則，配置的排隊規則生效時由qdisc_sleeping設置*/
struct Qdisc *qdisc;
/*當前配置的排隊規則，生效時將被設置到qdisc*/
struct Qdisc *qdisc_sleeping;
/*通過鏈表方式記錄配置所在網絡的所有排隊規則*/
struct list_head qdisc_list;
/*可在設備發送隊列中排隊的最大數據包*/
unsigned long tx_queue_len; /* Max frames per queue allowed */
/* Partially transmitted GSO packet. */
struct sk_buff *gso_skb;
/* ingress path synchronizer */
spinlock_t ingress_lock;
/*數據包輸入的排隊規則*/
struct Qdisc *qdisc_ingress;
/*
* One part is mostly used on xmit path (device)
*/
/* hard_start_xmit synchronizer */
spinlock_t _xmit_lock ____cacheline_aligned_in_smp;
/* cpu id of processor entered to hard_start_xmit or -1,
if nobody entered there.
*/
int xmit_lock_owner;
void *priv; /* pointer to private data */
/*驅動提供給上一層發送數據包的接口，在發送數據包時必定會調用該接口*/
int (*hard_start_xmit) (struct sk_buff *skb,
struct net_device *dev);
/* These may be needed for future network-power-down code. */
unsigned long trans_start; /* Time (in jiffies) of last Tx */
/*網絡層確定傳輸已經超時，而調用驅動程序的tx_timeout接口的最短時間*/
int watchdog_timeo; /* used by dev_watchdog() */
/*用於檢測網絡設備處於正常的工作狀態時，是否存在由於關閉隊列功能
而導致發送超時的情況，一旦發生以上狀況，就調用網絡設備驅動的tx_timeout
接口處理*/
struct timer_list watchdog_timer;
/*
* refcnt is a very hot point, so align it on SMP
*/
/* Number of references to this device */
atomic_t refcnt ____cacheline_aligned_in_smp;
/* delayed register/unregister */
/*用來連接net_todo_list鏈表，包含已經注銷即將結束的網絡設備*/
struct list_head todo_list;
/* device index hash chain */
/*根據網絡設備的索引，以散列表的形式組織到dev_index_hlist中*/
struct hlist_node index_hlist;
/* register/unregister state machine */
enum { NETREG_UNINITIALIZED=0,
NETREG_REGISTERED, /* completed register_netdevice */
NETREG_UNREGISTERING, /* called unregister_netdevice */
NETREG_UNREGISTERED, /* completed unregister todo */
NETREG_RELEASED, /* called free_netdev */
} reg_state;
/* Called after device is detached from network. */
void (*uninit)(struct net_device *dev);
/* Called after last user reference disappears. */
void (*destructor)(struct net_device *dev);
/* Pointers to interface service routines. */
/*啟用設備函數指針，完成那個注冊所需的系統資源，打開硬件極其所有
設備*/
int (*open)(struct net_device *dev);
int (*stop)(struct net_device *dev);
#define HAVE_NETDEV_POLL
/*根據先前檢測到的源和目標硬件地址創建硬件首部*/
int (*hard_header) (struct sk_buff *skb,
struct net_device *dev,
unsigned short type,
void *daddr,
void *saddr,
unsigned len);
/*用來在傳輸包之前，ARP解析完成之後，重建硬件首部*/
int (*rebuild_header)(struct sk_buff *skb);
#define HAVE_MULTICAST
/*將組播地址列表更新到網絡設備中*/
void (*set_multicast_list)(struct net_device *dev);
#define HAVE_SET_MAC_ADDR
/*修改硬件地址接口，需要網絡設備支持該功能*/
int (*set_mac_address)(struct net_device *dev,
void *addr);
#define HAVE_PRIVATE_IOCTL
int (*do_ioctl)(struct net_device *dev,
struct ifreq *ifr, int cmd);
#define HAVE_SET_CONFIG
int (*set_config)(struct net_device *dev,
struct ifmap *map);
#define HAVE_HEADER_CACHE
/*根據ARP查詢的結果填充hh_cache結構*/
int (*hard_header_cache)(struct neighbour *neigh,
struct hh_cache *hh);
void (*header_cache_update)(struct hh_cache *hh,
struct net_device *dev,
unsigned char * haddr);
#define HAVE_CHANGE_MTU
int (*change_mtu)(struct net_device *dev, int new_mtu);
#define HAVE_TX_TIMEOUT
void (*tx_timeout) (struct net_device *dev);
void (*vlan_rx_register)(struct net_device *dev,
struct vlan_group *grp);
void (*vlan_rx_add_vid)(struct net_device *dev,
unsigned short vid);
void (*vlan_rx_kill_vid)(struct net_device *dev,
unsigned short vid);
int (*hard_header_parse)(struct sk_buff *skb,
unsigned char *haddr);
/*設置鄰居子系統相關的參數*/
int (*neigh_setup)(struct net_device *dev, struct neigh_parms *);
#ifdef CONFIG_NETPOLL
/*網絡設備netpoll信息塊*/
struct netpoll_info *npinfo;
#endif
#ifdef CONFIG_NET_POLL_CONTROLLER
/*該函數在禁止中斷的情況下，要求驅動程序以輪詢模式在接口上查詢事件*/
void (*poll_controller)(struct net_device *dev);
#endif
/* bridge stuff */
struct net_bridge_port *br_port;
/* class/net/name entry */
struct class_device class_dev;
/* space for optional statistics and wireless sysfs groups */
struct attribute_group *sysfs_groups[3];
};
網卡驅動的注冊是在e100_init_modle中，
static int __init e100_init_module(void)
{
if(((1 << debug) - 1) & NETIF_MSG_DRV) {
printk(KERN_INFO PFX "%s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
printk(KERN_INFO PFX "%s\n", DRV_COPYRIGHT);
}
return pci_register_driver(&e100_driver);
}
可見，網卡驅動也就是和一般的PCI驅動編寫一樣。
static struct pci_driver e100_driver = {
.name = DRV_NAME,
.id_table = e100_id_table,
.probe = e100_probe,
.remove = __devexit_p(e100_remove),
#ifdef CONFIG_PM
/* Power Management hooks */
.suspend = e100_suspend,
.resume = e100_resume,
#endif
.shutdown = e100_shutdown,
.err_handler = &e100_err_handler,
};
如果網絡設備驅動程序被編譯進內核，則將在啟動時被初始化，在運行時作為模塊被加載。無論初始化是否被發生，由驅動程序控制的網絡設備都會被注冊。這種情形適用於所有的總線類型，無論是總線體系結構還是模塊初始��代碼調用注冊函數，結果都是一樣的。PCI設備驅動程序加載以至執行pci_drive->probe()函數。我們看看e100網卡的驅動注冊過程：
static int __devinit e100_probe(struct pci_dev *pdev,
const struct pci_device_id *ent)
{
struct net_device *netdev;
struct nic *nic;
int err;
/*分配設備數據結構*/
if(!(netdev = alloc_etherdev(sizeof(struct nic)))) {
if(((1 << debug) - 1) & NETIF_MSG_PROBE)
printk(KERN_ERR PFX "Etherdev alloc failed, abort.\n");
return -ENOMEM;
}
/*初始化設備*/
netdev->open = e100_open;
netdev->stop = e100_close;
/*e100網絡設備的hard_start_xmit接口實現，最終將數據包輸出到硬件*/
netdev->hard_start_xmit = e100_xmit_frame;
netdev->get_stats = e100_get_stats;
netdev->set_multicast_list = e100_set_multicast_list;
netdev->set_mac_address = e100_set_mac_address;
netdev->change_mtu = e100_change_mtu;
netdev->do_ioctl = e100_do_ioctl;
SET_ETHTOOL_OPS(netdev, &e100_ethtool_ops);
netdev->tx_timeout = e100_tx_timeout;
netdev->watchdog_timeo = E100_WATCHDOG_PERIOD;
netdev->poll = e100_poll;
netdev->weight = E100_NAPI_WEIGHT;
#ifdef CONFIG_NET_POLL_CONTROLLER
/*為了實現netpoll接收報文功能，需要實現下面的函數調用，該函數
用來模擬網絡設備發生中斷，進行中斷處理*/
netdev->poll_controller = e100_netpoll;
#endif
strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
/*在alloc_etherdev中設置的私有屬性,即結構nic，在這裡提出來*/
nic = netdev_priv(netdev);
/*初始化該nic*/
nic->netdev = netdev;
nic->pdev = pdev;
nic->msg_enable = (1 << debug) - 1;
/*設置PCI設備私有數據為網絡設備結構實例*/
pci_set_drvdata(pdev, netdev);
/* Initialize device before it's used by a driver. Ask low-level code
* to enable I/O and memory. Wake up the device if it was suspended.
* Beware, this function can fail.*/
if((err = pci_enable_device(pdev))) {
DPRINTK(PROBE, ERR, "Cannot enable PCI device, aborting.\n");
goto err_out_free_dev;
}
if(!(pci_resource_flags(pdev, 0) & IORESOURCE_MEM)) {
DPRINTK(PROBE, ERR, "Cannot find proper PCI device "
"base address, aborting.\n");
err = -ENODEV;
goto err_out_disable_pdev;
}
/*保留資源，包括I/O和內存*/
if((err = pci_request_regions(pdev, DRV_NAME))) {
DPRINTK(PROBE, ERR, "Cannot obtain PCI resources, aborting.\n");
goto err_out_disable_pdev;
}
/*DMA相關,探測設備的DMA能力，如果設備支持DMA,
返回0*/
if((err = pci_set_dma_mask(pdev, DMA_32BIT_MASK))) {
DPRINTK(PROBE, ERR, "No usable DMA configuration, aborting.\n");
goto err_out_free_res;
}
SET_MODULE_OWNER(netdev);
SET_NETDEV_DEV(netdev, &pdev->dev);
/*控制狀態寄存器映射內存資源*/
nic->csr = ioremap(pci_resource_start(pdev, 0), sizeof(struct csr));
if(!nic->csr) {
DPRINTK(PROBE, ERR, "Cannot map device registers, aborting.\n");
err = -ENOMEM;
goto err_out_free_res;
}
if(ent->driver_data)
nic->flags |= ich;
else
nic->flags &= ~ich;
/*初始化nic相關字段*/
e100_get_defaults(nic);
/* locks must be initialized before calling hw_reset */
spin_lock_init(&nic->cb_lock);
spin_lock_init(&nic->cmd_lock);
spin_lock_init(&nic->mdio_lock);
/* Reset the device before pci_set_master() in case device is in some
* funky state and has an interrupt pending - hint: we don't have the
* interrupt handler registered yet. */
/*設備復位，寫相關寄存器方式實現*/
e100_hw_reset(nic);
/*啟用設備*/
pci_set_master(pdev);
/*初始化兩個軟件時鐘*/
init_timer(&nic->watchdog);
nic->watchdog.function = e100_watchdog;
nic->watchdog.data = (unsigned long)nic;
init_timer(&nic->blink_timer);
nic->blink_timer.function = e100_blink_led;
nic->blink_timer.data = (unsigned long)nic;
/*初始化工作隊列*/
INIT_WORK(&nic->tx_timeout_task, e100_tx_timeout_task);
/*從DMA區分配*/
if((err = e100_alloc(nic))) {
DPRINTK(PROBE, ERR, "Cannot alloc driver memory, aborting.\n");
goto err_out_iounmap;
}
/*讀取網卡的EEPROM。其中存放這網卡的MAC地址
*/
if((err = e100_eeprom_load(nic)))
goto err_out_free;
/*初始化nic的物理信息*/
e100_phy_init(nic);
memcpy(netdev->dev_addr, nic->eeprom, ETH_ALEN);
memcpy(netdev->perm_addr, nic->eeprom, ETH_ALEN);
/*驗證網卡的MAC地址是否格式正確*/
if(!is_valid_ether_addr(netdev->perm_addr)) {
DPRINTK(PROBE, ERR, "Invalid MAC address from "
"EEPROM, aborting.\n");
err = -EAGAIN;
goto err_out_free;
}
/* Wol magic packet can be enabled from eeprom */
if((nic->mac >= mac_82558_D101_A4) &&
(nic->eeprom[eeprom_id] & eeprom_id_wol))
nic->flags |= wol_magic;
/* ack any pending wake events, disable PME */
/*,這個函數的第二個參數表示一種電源狀態
PME#就是Power Management Event Signal,即電源管理事件信號.)PME#信號是PCI Power Spec中出鏡率最高的一個名詞.如果一個設備希望改變它的電源狀態,它就可以發送一個PME#信號.而設備是否允許發送信號也是有開關的,並且每種狀態都有一個開關
第三個參數是表示開還是關.即傳遞1進去就是enable,傳遞0進去就是disable*/
err = pci_enable_wake(pdev, 0, 0);
if (err)
DPRINTK(PROBE, ERR, "Error clearing wake event\n");
/*網絡設備的名稱前加上eth*/
strcpy(netdev->name, "eth%d");
/*注冊網絡設備*/
if((err = register_netdev(netdev))) {
DPRINTK(PROBE, ERR, "Cannot register net device, aborting.\n");
goto err_out_free;
}
DPRINTK(PROBE, INFO, "addr 0x%llx, irq %d, "
"MAC addr %02X:%02X:%02X:%02X:%02X:%02X\n",
(unsigned long long)pci_resource_start(pdev, 0), pdev->irq,
netdev->dev_addr[0], netdev->dev_addr[1], netdev->dev_addr[2],
netdev->dev_addr[3], netdev->dev_addr[4], netdev->dev_addr[5]);
return 0;
err_out_free:
e100_free(nic);
err_out_iounmap:
iounmap(nic->csr);
err_out_free_res:
pci_release_regions(pdev);
err_out_disable_pdev:
pci_disable_device(pdev);
err_out_free_dev:
pci_set_drvdata(pdev, NULL);
free_netdev(netdev);
return err;
}
其輔助函數：
分配網絡設備結構
/*傳入的參數為nic結構的大小*/
struct net_device *alloc_etherdev(int sizeof_priv)
{
return alloc_netdev(sizeof_priv, "eth%d", ether_setup);
}
struct net_device *alloc_netdev(int sizeof_priv, const char *name,
void (*setup)(struct net_device *))
{
void *p;
struct net_device *dev;
int alloc_size;
BUG_ON(strlen(name) >= sizeof(dev->name));
/* ensure 32-byte alignment of both the device and private area */
/*計算分配的大小為設備結構大小加上nic結構大小*/
alloc_size = (sizeof(*dev) + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST;
alloc_size += sizeof_priv + NETDEV_ALIGN_CONST;
/*分配空間*/
p = kzalloc(alloc_size, GFP_KERNEL);
if (!p) {
printk(KERN_ERR "alloc_netdev: Unable to allocate device.\n");
return NULL;
}
dev = (struct net_device *)
(((long)p + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST);
/*計算padd大小為結構大小減去對其的數據大小*/
dev->padded = (char *)dev - (char *)p;
if (sizeof_priv)
/*私有數據為nic結構的起始地址*/
dev->priv = netdev_priv(dev);
/*調用參數中的函數指針，初始化設備結構*/
setup(dev);
strcpy(dev->name, name);
return dev;
}
/*分配設備結構時調用，用於初始化該設備結構*/
void ether_setup(struct net_device *dev)
{
dev->change_mtu = eth_change_mtu;
dev->hard_header = eth_header;
dev->rebuild_header = eth_rebuild_header;
dev->set_mac_address = eth_mac_addr;
dev->hard_header_cache = eth_header_cache;
dev->header_cache_update= eth_header_cache_update;
dev->hard_header_parse = eth_header_parse;
dev->type = ARPHRD_ETHER;
dev->hard_header_len = ETH_HLEN;
dev->mtu = ETH_DATA_LEN;
dev->addr_len = ETH_ALEN;
dev->tx_queue_len = 1000; /* Ethernet wants good queues */
dev->flags = IFF_BROADCAST|IFF_MULTICAST;
memset(dev->broadcast, 0xFF, ETH_ALEN);
}
注冊網絡設備的實際操作由register_netdev(netdev)調用register_netdevice()完成
int register_netdevice(struct net_device *dev)
{
struct hlist_head *head;
struct hlist_node *p;
int ret;
BUG_ON(dev_boot_phase);
ASSERT_RTNL();
/*2.6內核支持內核搶占，該函數檢查是否需要從新調度
如果是，則進行調度，無論此時進行執行在內核空間還是
用戶空間*/
might_sleep();
/*初始化設備的各個字段*/
/* When net_device's are persistent, this will be fatal. */
BUG_ON(dev->reg_state != NETREG_UNINITIALIZED);
spin_lock_init(&dev->queue_lock);
spin_lock_init(&dev->_xmit_lock);
dev->xmit_lock_owner = -1;
#ifdef CONFIG_NET_CLS_ACT
spin_lock_init(&dev->ingress_lock);
#endif
dev->iflink = -1;
/* Init, if this function is available */
/*如果有init函數，調用該函數進行初始化*/
if (dev->init) {
ret = dev->init(dev);
if (ret) {
if (ret > 0)
ret = -EIO;
goto out;
}
}
/*檢測待注冊的網絡設備名是否有效*/
if (!dev_valid_name(dev->name)) {
ret = -EINVAL;
goto out;
}
/*為設備分配一個唯一索引號和一個用於虛擬隧道設備
的唯一標識。*/
dev->ifindex = dev_new_index();
if (dev->iflink == -1)
dev->iflink = dev->ifindex;
/* Check for existence of name */
/*將網絡設備添加到dev_name_head散列表中，並檢測是否
存在同名的網絡設備*/
head = dev_name_hash(dev->name);
hlist_for_each(p, head) {
struct net_device *d
= hlist_entry(p, struct net_device, name_hlist);
if (!strncmp(d->name, dev->name, IFNAMSIZ)) {
ret = -EEXIST;
goto out;
}
}
/* Fix illegal SG+CSUM combinations. */
/*只有在網絡設備支持校驗和計算的情況下，網絡設備才能支持SG類型的聚合分散I/O
因為SG類型的聚合分散I/O特性沒有傳輸層硬件檢驗和支持是無用的*/
if ((dev->features & NETIF_F_SG) &&
!(dev->features & NETIF_F_ALL_CSUM)) {
printk(KERN_NOTICE "%s: Dropping NETIF_F_SG since no checksum feature.\n",
dev->name);
dev->features &= ~NETIF_F_SG;
}
/* TSO requires that SG is present as well. */
/*TSO需要SG類型的聚合分散性I/O的支持，因此在後者不被支持時也將被禁用*/
if ((dev->features & NETIF_F_TSO) &&
!(dev->features & NETIF_F_SG)) {
printk(KERN_NOTICE "%s: Dropping NETIF_F_TSO since no SG feature.\n",
dev->name);
dev->features &= ~NETIF_F_TSO;
}
/*UFO需要NETIF_F_HW_CSUM和SG類型的聚合分散I/O的支持，因此在後者不被支持的情況下
也將被禁用*/
if (dev->features & NETIF_F_UFO) {
if (!(dev->features & NETIF_F_HW_CSUM)) {
printk(KERN_ERR "%s: Dropping NETIF_F_UFO since no "
"NETIF_F_HW_CSUM feature.\n",
dev->name);
dev->features &= ~NETIF_F_UFO;
}
if (!(dev->features & NETIF_F_SG)) {
printk(KERN_ERR "%s: Dropping NETIF_F_UFO since no "
"NETIF_F_SG feature.\n",
dev->name);
dev->features &= ~NETIF_F_UFO;
}
}
/*
* nil rebuild_header routine,
* that should be never called and used as just bug trap.
*/
/*初始化網絡設備用於重建硬件首部的rebuild_header接口
*/
if (!dev->rebuild_header)
dev->rebuild_header = default_rebuild_header;
/*將網絡設備的注冊信息注冊到sysfs文件系統中*/
ret = netdev_register_sysfs(dev);
if (ret)
goto out;
/*設置網絡設備的狀態，表示注冊已經完成*/
dev->reg_state = NETREG_REGISTERED;
/*
* Default initial state at registry is that the
* device is present.
*/
/*設置相應位，表示設備對系統是可用的*/
set_bit(__LINK_STATE_PRESENT, &dev->state);
/*下面為初始化網絡設備排隊規則，並注冊到網絡設備的
鏈表和相關散列表中*/
dev->next = NULL;
dev_init_scheduler(dev);
write_lock_bh(&dev_base_lock);
*dev_tail = dev;
dev_tail = &dev->next;
hlist_add_head(&dev->name_hlist, head);
hlist_add_head(&dev->index_hlist, dev_index_hash(dev->ifindex));
dev_hold(dev);
write_unlock_bh(&dev_base_lock);
/* Notify protocols, that a new device appeared. */
/*通知所有對設備注冊感興趣的其他內核模塊*/
raw_notifier_call_chain(&netdev_chain, NETDEV_REGISTER, dev);
ret = 0;
out:
return ret;
}
PCI驅動中的其他函數意義同其名，我們看看掛起操作e100_suspend
static int e100_suspend(struct pci_dev *pdev, pm_message_t state)
{
struct net_device *netdev = pci_get_drvdata(pdev);
struct nic *nic = netdev_priv(netdev);
/*如果網絡設備處於激活狀態，則等待網絡設備完成輪詢接收數據包*/
if (netif_running(netdev))
netif_poll_disable(nic->netdev);
/*刪除監視網絡設備工作狀態的定時器*/
del_timer_sync(&nic->watchdog);
/*使設備驅動處於不可傳遞數據狀態，並關閉網絡設備的隊列功能*/
netif_carrier_off(nic->netdev);
netif_device_detach(netdev);
pci_save_state(pdev);
/*
這個函數的第二個參數表示一種電源狀態,咱們看到傳遞的一次是PCI_D3hot,一次是PCI_D3cold,
這就是使得設備可以從這兩種狀態中產生PME#信號.(PME#就是Power Management Event Signal,即電源管理事件信號
.)PME#信號是PCI Power Spec中出鏡率最高的一個名詞.如果一個設備希望改變它的電源狀態,它就可以發送
一個PME#信號.而設備是否允許發送信號也是有開關的,並且每種狀態都有一個開關.
所以這裡的做法就是為D3hot和D3cold打開開關.而這裡pci_enable_wake的第三個參數是表示開還是關.
即傳遞1進去就是enable,傳遞0進去就是disable.
*/
if ((nic->flags & wol_magic) | e100_asf(nic)) {
pci_enable_wake(pdev, PCI_D3hot, 1);
pci_enable_wake(pdev, PCI_D3cold, 1);
} else {
pci_enable_wake(pdev, PCI_D3hot, 0);
pci_enable_wake(pdev, PCI_D3cold, 0);
}
/*禁用設備*/
pci_disable_device(pdev);
/*釋放中斷*/
free_irq(pdev->irq, netdev);
/*設置PCI的電源狀態*/
pci_set_power_state(pdev, PCI_D3hot);
return 0;
}
這樣，網絡設備的驅動框架就搭建起來了，驅動程序在模塊初始化函數中注冊網卡的PCI驅動，在probe函數中注冊網卡設備驅動，初始化相關數據結構和函數指針。對於特定的網卡需要特定的數據結構來保存信息，硬件相關的操作需要按照對應網卡的約定來實現。對於e100系列網卡，數據結構nic保存了該網卡的所有信息。另外net_device中提供的函數指針在e100_probe中做了初始化，如e100_open，依據他們的名字我們可以猜到他們的意思和用途（e100_open做網卡的打開、啟動、中斷的注冊等操作）。這裡就不再深入了，如果對他們的實現細節感興趣，需要參看其網卡的硬件手冊。
後面我們在分析上層代碼中會遇到一些操作特定網卡的函數指針，在這裡就能找到其實現。