Linux网络协议栈之驱动框架

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我是靠谱客的博主强健奇迹，最近开发中收集的这篇文章主要介绍Linux网络协议栈之驱动框架，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

Linux网络协议栈之驱动框架

作者：bullbat

网卡驱动可以以模块的方式加载也可以内核初始化的时候加载，我们选定e100系列的网卡进行说明网卡驱动的一般框架。

网卡设备通用数据结构：

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.

/*网络设备名*/

char name[IFNAMSIZ];

/* device name hash chain */

/*根据网络设备名以散列表的形式组织到dev_name_head散列表中，这样就可以通过网络

设备名快速地定位到网络设备*/

struct hlist_node name_hlist;

* I/O specific fields

* FIXME: Merge these and struct ifmap into one

/*网络设备共享内存的起始和终止地址*/

unsigned long mem_end; /* shared mem end */

unsigned long mem_start; /* shared mem start */

/*网络接口I/O基地址，在探测设备时被初始化ifconfig命令可显示和修改

当前命令*/

unsigned long base_addr; /* device I/O address */

/*分配给设备的中断号，一般在初始化设备时被初始化*/

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.

/*指定在多端口设备上使用那个端口*/

unsigned char if_port; /* Selectable AUI, TP,..*/

/*为设备分配的DMA通道*/

unsigned char dma; /* DMA channel */

/*设备状态*/

unsigned long state;

/*网络设备组织*/

struct net_device *next;

/*驱动程序的初始化函数*/

/* 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)

/*用于连接那些已经调度有数据报输出的网络设备指针*/

struct net_device *next_sched;

/* Interface index. Unique device identifier */

/*网络设备的索引号*/

int ifindex;

/*网络设备的唯一标识，主要用于虚拟隧道设备*/

int iflink;

/*提供给应用程序获得接口统计信息的接口*/

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 */

/*无线网相关*/

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) */

/*记录当前网络设备IFF_PROMISC和IFF_ALLMULTI的状态，用来配合flags的设置*/

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，通常初始化时从硬件中读出来*/

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 */

/*设置网络设备混杂模式计数器*/

int promiscuity;

/*设置网络设备接收所有组播报的计数器，每次设置或是退出操作，该字段

都会相应的加或减1，为0时，网络设备才真正不再接收组播报*/

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())

/*该结构实例通过该字段连接到softnet_data的poll_list成员上*/

struct list_head poll_list ____cacheline_aligned_in_smp;

/* Link to poll list */

/*轮询模式操作接口*/

int (*poll) (struct net_device *dev, int *quota);

/*读取数据包的配额，动态变化，由netdev_budget初始化，每次从网络设备中读取数据包后，

会从中减去本次读取的数据包数，当该配额等于或小于0时，结束当前轮询等待下层轮询

这样即使某个网络设备有大量的数据包输入，也能保证其他网络设备能及时收到数据包

在输入时，遍历网络设备轮询队列，从选定的网络设备中读取数据包，一旦已经读取的数据

包的数量操作配额，即停止本次读取，将该网络设备移至网络设备轮询队列的队尾，等待

下次轮询*/

int quota;

/*数据包输入软中断中，单个网络读取数据包的配额*/

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;

/*当前使用的根排队规则，配置的排队规则生效时由qdisc_sleeping设置*/

struct Qdisc *qdisc;

/*当前配置的排队规则，生效时将被设置到qdisc*/

struct Qdisc *qdisc_sleeping;

/*通过链表方式记录配置所在网络的所有排队规则*/

struct list_head qdisc_list;

/*可在设备发送队列中排队的最大数据包*/

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;

/*数据包输入的排队规则*/

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 */

/*驱动提供给上一层发送数据包的接口，在发送数据包时必定会调用该接口*/

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 */

/*网络层确定传输已经超时，而调用驱动程序的tx_timeout接口的最短时间*/

int watchdog_timeo; /* used by dev_watchdog() */

/*用于检测网络设备处于正常的工作状态时，是否存在由于关闭队列功能

而导致发送超时的情况，一旦发生以上状况，就调用网络设备驱动的tx_timeout

接口处理*/

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 */

/*用来连接net_todo_list链表，包含已经注销即将结束的网络设备*/

struct list_head todo_list;

/* device index hash chain */

/*根据网络设备的索引，以散列表的形式组织到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. */

/*启用设备函数指针，完成那个注册所需的系统资源，打开硬件极其所有

设备*/

int (*open)(struct net_device *dev);

int (*stop)(struct net_device *dev);

#define HAVE_NETDEV_POLL

/*根据先前检测到的源和目标硬件地址创建硬件首部*/

int (*hard_header) (struct sk_buff *skb,

struct net_device *dev,

unsigned short type,

void *daddr,

void *saddr,

unsigned len);

/*用来在传输包之前，ARP解析完成之后，重建硬件首部*/

int (*rebuild_header)(struct sk_buff *skb);

#define HAVE_MULTICAST

/*将组播地址列表更新到网络设备中*/

void (*set_multicast_list)(struct net_device *dev);

#define HAVE_SET_MAC_ADDR

/*修改硬件地址接口，需要网络设备支持该功能*/

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

/*根据ARP查询的结果填充hh_cache结构*/

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);

/*设置邻居子系统相关的参数*/

int (*neigh_setup)(struct net_device *dev, struct neigh_parms *);

#ifdef CONFIG_NETPOLL

/*网络设备netpoll信息块*/

struct netpoll_info *npinfo;

#endif

#ifdef CONFIG_NET_POLL_CONTROLLER

/*该函数在禁止中断的情况下，要求驱动程序以轮询模式在接口上查询事件*/

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];

};

网卡驱动的注册是在e100_init_modle中，

static int __init e100_init_module(void)

{

if(((1 << debug) - 1) & NETIF_MSG_DRV) {

printk(KERN_INFO PFX "%s, %sn", DRV_DESCRIPTION, DRV_VERSION);

printk(KERN_INFO PFX "%sn", DRV_COPYRIGHT);

}

return pci_register_driver(&e100_driver);

}

可见，网卡驱动也就是和一般的PCI驱动编写一样。

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,

};

如果网络设备驱动程序被编译进内核，则将在启动时被初始化，在运行时作为模块被加载。无论初始化是否被发生，由驱动程序控制的网络设备都会被注册。这种情形适用于所有的总线类型，无论是总线体系结构还是模块初始化代码调用注册函数，结果都是一样的。PCI设备驱动程序加载以至执行pci_drive->probe()函数。我们看看e100网卡的驱动注册过程：

static int __devinit e100_probe(struct pci_dev *pdev,

const struct pci_device_id *ent)

{

struct net_device *netdev;

struct nic *nic;

int err;

/*分配设备数据结构*/

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;

}

/*初始化设备*/

netdev->open = e100_open;

netdev->stop = e100_close;

/*e100网络设备的hard_start_xmit接口实现，最终将数据包输出到硬件*/

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

/*为了实现netpoll接收报文功能，需要实现下面的函数调用，该函数

用来模拟网络设备发生中断，进行中断处理*/

netdev->poll_controller = e100_netpoll;

#endif

strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);

/*在alloc_etherdev中设置的私有属性,即结构nic，在这里提出来*/

nic = netdev_priv(netdev);

/*初始化该nic*/

nic->netdev = netdev;

nic->pdev = pdev;

nic->msg_enable = (1 << debug) - 1;

/*设置PCI设备私有数据为网络设备结构实例*/

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;

}

/*保留资源，包括I/O和内存*/

if((err = pci_request_regions(pdev, DRV_NAME))) {

DPRINTK(PROBE, ERR, "Cannot obtain PCI resources, aborting.n");

goto err_out_disable_pdev;

}

/*DMA相关,探测设备的DMA能力，如果设备支持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);

/*控制状态寄存器映射内存资源*/

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相关字段*/

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. */

/*设备复位，写相关寄存器方式实现*/

e100_hw_reset(nic);

/*启用设备*/

pci_set_master(pdev);

/*初始化两个软件时钟*/

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;

/*初始化工作队列*/

INIT_WORK(&nic->tx_timeout_task, e100_tx_timeout_task);

/*从DMA区分配*/

if((err = e100_alloc(nic))) {

DPRINTK(PROBE, ERR, "Cannot alloc driver memory, aborting.n");

goto err_out_iounmap;

}

/*读取网卡的EEPROM。其中存放这网卡的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);

/*验证网卡的MAC地址是否格式正确*/

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 */

/*,这个函数的第二个参数表示一种电源状态

PME#就是Power Management Event Signal,即电源管理事件信号.)PME#信号是PCI Power Spec中出镜率最高的一个名词.如果一个设备希望改变它的电源状态,它就可以发送一个PME#信号.而设备是否允许发送信号也是有开关的,并且每种状态都有一个开关

第三个参数是表示开还是关.即传递1进去就是enable,传递0进去就是disable*/

err = pci_enable_wake(pdev, 0, 0);

if (err)

DPRINTK(PROBE, ERR, "Error clearing wake eventn");

/*网络设备的名称前加上eth*/

strcpy(netdev->name, "eth%d");

/*注册网络设备*/

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:%02Xn",

(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;

}

其辅助函数：

分配网络设备结构

/*传入的参数为nic结构的大小*/

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 */

/*计算分配的大小为设备结构大小加上nic结构大小*/

alloc_size = (sizeof(*dev) + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST;

alloc_size += sizeof_priv + NETDEV_ALIGN_CONST;

/*分配空间*/

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);

/*计算padd大小为结构大小减去对其的数据大小*/

dev->padded = (char *)dev - (char *)p;

if (sizeof_priv)

/*私有数据为nic结构的起始地址*/

dev->priv = netdev_priv(dev);

/*调用参数中的函数指针，初始化设备结构*/

setup(dev);

strcpy(dev->name, name);

return dev;

}

/*分配设备结构时调用，用于初始化该设备结构*/

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);

}

注册网络设备的实际操作由register_netdev(netdev)调用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内核支持内核抢占，该函数检查是否需要从新调度

如果是，则进行调度，无论此时进行执行在内核空间还是

用户空间*/

might_sleep();

/*初始化设备的各个字段*/

/* 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函数，调用该函数进行初始化*/

if (dev->init) {

ret = dev->init(dev);

if (ret) {

if (ret > 0)

ret = -EIO;

goto out;

}

/*检测待注册的网络设备名是否有效*/

if (!dev_valid_name(dev->name)) {

ret = -EINVAL;

goto out;

}

/*为设备分配一个唯一索引号和一个用于虚拟隧道设备

的唯一标识。*/

dev->ifindex = dev_new_index();

if (dev->iflink == -1)

dev->iflink = dev->ifindex;

/* Check for existence of name */

/*将网络设备添加到dev_name_head散列表中，并检测是否

存在同名的网络设备*/

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. */

/*只有在网络设备支持校验和计算的情况下，网络设备才能支持SG类型的聚合分散I/O

因为SG类型的聚合分散I/O特性没有传输层硬件检验和支持是无用的*/

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类型的聚合分散性I/O的支持，因此在后者不被支持时也将被禁用*/

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类型的聚合分散I/O的支持，因此在后者不被支持的情况下

也将被禁用*/

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.

/*初始化网络设备用于重建硬件首部的rebuild_header接口

if (!dev->rebuild_header)

dev->rebuild_header = default_rebuild_header;

/*将网络设备的注册信息注册到sysfs文件系统中*/

ret = netdev_register_sysfs(dev);

if (ret)

goto out;

/*设置网络设备的状态，表示注册已经完成*/

dev->reg_state = NETREG_REGISTERED;

* Default initial state at registry is that the

* device is present.

/*设置相应位，表示设备对系统是可用的*/

set_bit(__LINK_STATE_PRESENT, &dev->state);

/*下面为初始化网络设备排队规则，并注册到网络设备的

链表和相关散列表中*/

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. */

/*通知所有对设备注册感兴趣的其他内核模块*/

raw_notifier_call_chain(&netdev_chain, NETDEV_REGISTER, dev);

ret = 0;

out:

return ret;

}

PCI驱动中的其他函数意义同其名，我们看看挂起操作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);

/*如果网络设备处于激活状态，则等待网络设备完成轮询接收数据包*/

if (netif_running(netdev))

netif_poll_disable(nic->netdev);

/*删除监视网络设备工作状态的定时器*/

del_timer_sync(&nic->watchdog);

/*使设备驱动处于不可传递数据状态，并关闭网络设备的队列功能*/

netif_carrier_off(nic->netdev);

netif_device_detach(netdev);

pci_save_state(pdev);

这个函数的第二个参数表示一种电源状态,咱们看到传递的一次是PCI_D3hot,一次是PCI_D3cold,

这就是使得设备可以从这两种状态中产生PME#信号.(PME#就是Power Management Event Signal,即电源管理事件信号

.)PME#信号是PCI Power Spec中出镜率最高的一个名词.如果一个设备希望改变它的电源状态,它就可以发送

一个PME#信号.而设备是否允许发送信号也是有开关的,并且每种状态都有一个开关.

所以这里的做法就是为D3hot和D3cold打开开关.而这里pci_enable_wake的第三个参数是表示开还是关.

即传递1进去就是enable,传递0进去就是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);

}

/*禁用设备*/

pci_disable_device(pdev);

/*释放中断*/

free_irq(pdev->irq, netdev);

/*设置PCI的电源状态*/

pci_set_power_state(pdev, PCI_D3hot);

return 0;

}

这样，网络设备的驱动框架就搭建起来了，驱动程序在模块初始化函数中注册网卡的PCI驱动，在probe函数中注册网卡设备驱动，初始化相关数据结构和函数指针。对于特定的网卡需要特定的数据结构来保存信息，硬件相关的操作需要按照对应网卡的约定来实现。对于e100系列网卡，数据结构nic保存了该网卡的所有信息。另外net_device中提供的函数指针在e100_probe中做了初始化，如e100_open，依据他们的名字我们可以猜到他们的意思和用途（e100_open做网卡的打开、启动、中断的注册等操作）。这里就不再深入了，如果对他们的实现细节感兴趣，需要参看其网卡的硬件手册。

后面我们在分析上层代码中会遇到一些操作特定网卡的函数指针，在这里就能找到其实现。