DM9000网卡驱动分析(转)

时间:2022-05-29 09:41:56

s3c6410自带的DM9000网卡驱动也是基于platform设备模型。

其定义的设备资源在arch/arm/mach-s3c64xx/mach-smdk6410中。有网卡的resource resource dm9000_resources[],还有一些板级信息,dm9000_plat_data dm9000_setup。
 
1.宏及参数  //板级、系统定义
 1 #define DM9000_PHY        0x40    /* PHY address 0x01 */
 2 
 3 #define CARDNAME    "dm9000"
 4 #define DRV_VERSION    "1.31"
 5 /*
 6  * Transmit timeout, default 5 seconds.
 7  */
 8 static int watchdog = 5000; //5s的延时时间
 9 module_param(watchdog, int, 0400);
10 MODULE_PARM_DESC(watchdog, "transmit timeout in milliseconds");
11 enum dm9000_type {  //开发板定义了三个DM9000类型
12     TYPE_DM9000E,    /* original DM9000 */
13     TYPE_DM9000A,
14     TYPE_DM9000B
15 };
2.模块注册
此处因为基于platform模型,采用platform_driver_register函数注册内核模块,当设备驱动与设备匹配真确后,转入执行dm9000_probe()函数,该函数包含真正的dm9000网卡驱动注册函数是register_netdev()函数。
1 static int __init dm9000_init(void)
2 {
3     printk(KERN_INFO "%s Ethernet Driver, V%s\n", CARDNAME, DRV_VERSION);
4 
5     return platform_driver_register(&dm9000_driver); //platform设备模型注册驱动
6 }

dm9000的platform设备驱动函数如下:

1 static struct platform_driver dm9000_driver = {
2     .driver    = {
3         .name = "dm9000",
4         .owner     = THIS_MODULE,
5         .pm     = &dm9000_drv_pm_ops,
6     },
7     .probe = dm9000_probe,
8     .remove = __devexit_p(dm9000_drv_remove),
9 };
3.dm9000_probe函数
主要完成网络设备的初始化,以及网卡驱动的注册register_netdev()
  1 static int __devinit  dm9000_probe(struct platform_device *pdev)
  2 {
  3     struct dm9000_plat_data *pdata = pdev->dev.platform_data;//驱动程序中获得系统定义的网卡板级信息
  4                                             //定义在/arch/arm/mach-s3c64xx/mach-smdk6410.c中。
  5     struct board_info *db;    /* Point a board information structure */
  6     struct net_device *ndev; //定义设备结构体
  7     const unsigned char *mac_src;
  8     int ret = 0;
  9     int iosize;
 10     int i;
 11     u32 id_val;
 12 
 13     /* Init network device */
 14 //分配生成net_device结构体  alloc_etherdev是alloc_netdev()针对以太网的快捷操作函数
 15     ndev = alloc_etherdev(sizeof(struct board_info)); 
 16 
 17 //判断是否分配正确
 18     if (!ndev) {
 19         dev_err(&pdev->dev, "could not allocate device.\n");
 20         return -ENOMEM;
 21     }
 22 //建立net_device到device的连接
 23     SET_NETDEV_DEV(ndev, &pdev->dev); 
 24 //内核输出信息
 25     dev_dbg(&pdev->dev, "dm9000_probe()\n");
 26 //函数netdev_priv直接返回了net_device结构末端地址,也就是网卡私有数据结构的起始地址。
 27     /* setup board info structure */
 28     db = netdev_priv(ndev);
 29 
 30     db->dev = &pdev->dev;
 31     db->ndev = ndev;
 32 
 33     spin_lock_init(&db->lock);//初始化自旋锁
 34     mutex_init(&db->addr_lock);
 35 
 36     INIT_DELAYED_WORK(&db->phy_poll, dm9000_poll_work); //??
 37 //获取平台设备资源 resource 地址空间、数据空间、中断信号 7号中断
 38     db->addr_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 39     db->data_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
 40     db->irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 41 //判断资源是否获取成功
 42     if (db->addr_res == NULL || db->data_res == NULL ||
 43      db->irq_res == NULL) {
 44         dev_err(db->dev, "insufficient resources\n");
 45         ret = -ENOENT;
 46         goto out;
 47     }
 48 //platform_get_resource的变体 同  platform_get_resource(pdev, IORESOURCE_IRQ, 1)
 49     db->irq_wake = platform_get_irq(pdev, 1); 
 50     if (db->irq_wake >= 0) {
 51         dev_dbg(db->dev, "wakeup irq %d\n", db->irq_wake);
 52                                                                                                          //前面获得中断号  申请中断
 53         ret = request_irq(db->irq_wake, dm9000_wol_interrupt,
 54                  IRQF_SHARED, dev_name(db->dev), ndev);
 55         if (ret) {
 56             dev_err(db->dev, "cannot get wakeup irq (%d)\n", ret);
 57         } else {
 58             /* test to see if irq is really wakeup capable */
 59             ret = set_irq_wake(db->irq_wake, 1);
 60             if (ret) {
 61                 dev_err(db->dev, "irq %d cannot set wakeup (%d)\n",
 62                     db->irq_wake, ret);
 63                 ret = 0;
 64             } else {
 65                 set_irq_wake(db->irq_wake, 0);
 66                 db->wake_supported = 1;
 67             }
 68         }
 69     }
 70 //IO资源分配大小  地址  为resource分配内存
 71     iosize = resource_size(db->addr_res);
 72     db->addr_req = request_mem_region(db->addr_res->start, iosize,
 73                      pdev->name); //内存申请
 74 
 75     if (db->addr_req == NULL) {
 76         dev_err(db->dev, "cannot claim address reg area\n");
 77         ret = -EIO;
 78         goto out;
 79     }
 80 
 81     db->io_addr = ioremap(db->addr_res->start, iosize);
 82 
 83     if (db->io_addr == NULL) {
 84         dev_err(db->dev, "failed to ioremap address reg\n");
 85         ret = -EINVAL;
 86         goto out;
 87     }
 88 
 89     iosize = resource_size(db->data_res);
 90     db->data_req = request_mem_region(db->data_res->start, iosize,
 91                      pdev->name);
 92 
 93     if (db->data_req == NULL) {
 94         dev_err(db->dev, "cannot claim data reg area\n");
 95         ret = -EIO;
 96         goto out;
 97     }
 98 
 99     db->io_data = ioremap(db->data_res->start, iosize);
100 
101     if (db->io_data == NULL) {
102         dev_err(db->dev, "failed to ioremap data reg\n");
103         ret = -EINVAL;
104         goto out;
105     }
106 //初始化net_device中的成员
107     /* fill in parameters for net-dev structure */
108     ndev->base_addr = (unsigned long)db->io_addr; //网络接口的IO基地址
109     ndev->irq    = db->irq_res->start;//中断号  ifconfig时会打印出这个值  也可通过这个修改
110 
111     /* ensure at least we have a default set of IO routines */
112     dm9000_set_io(db, iosize); 
113 
114     /* check to see if anything is being over-ridden */
115     if (pdata != NULL) {
116         /* check to see if the driver wants to over-ride the
117          * default IO width */
118 //检测与板级信息是否相同
119         if (pdata->flags & DM9000_PLATF_8BITONLY)
120             dm9000_set_io(db, 1);
121 
122         if (pdata->flags & DM9000_PLATF_16BITONLY)
123             dm9000_set_io(db, 2);
124 
125         if (pdata->flags & DM9000_PLATF_32BITONLY)
126             dm9000_set_io(db, 4);
127 
128         /* check to see if there are any IO routine
129          * over-rides */
130 
131         if (pdata->inblk != NULL)
132             db->inblk = pdata->inblk;
133 
134         if (pdata->outblk != NULL)
135             db->outblk = pdata->outblk;
136 
137         if (pdata->dumpblk != NULL)
138             db->dumpblk = pdata->dumpblk;
139 
140         db->flags = pdata->flags;
141     }
142 
143 #ifdef CONFIG_DM9000_FORCE_SIMPLE_PHY_POLL
144     db->flags |= DM9000_PLATF_SIMPLE_PHY;
145 #endif
146 
147     dm9000_reset(db);
148 
149     /* try multiple times, DM9000 sometimes gets the read wrong */
150     for (i = 0; i < 8; i++) {  //宏定义在dm9000.h中
151         id_val = ior(db, DM9000_VIDL);
152         id_val |= (u32)ior(db, DM9000_VIDH) << 8;
153         id_val |= (u32)ior(db, DM9000_PIDL) << 16;
154         id_val |= (u32)ior(db, DM9000_PIDH) << 24;
155 
156         if (id_val == DM9000_ID)
157             break;
158         dev_err(db->dev, "read wrong id 0x%08x\n", id_val);
159     }
160 
161     if (id_val != DM9000_ID) {
162         dev_err(db->dev, "wrong id: 0x%08x\n", id_val);
163         ret = -ENODEV;
164         goto out;
165     }
166 
167     /* Identify what type of DM9000 we are working on */
168 
169     id_val = ior(db, DM9000_CHIPR);
170     dev_dbg(db->dev, "dm9000 revision 0x%02x\n", id_val);
171 
172     switch (id_val) {
173     case CHIPR_DM9000A:
174         db->type = TYPE_DM9000A;
175         break;
176     case CHIPR_DM9000B:
177         db->type = TYPE_DM9000B;
178         break;
179     default:
180         dev_dbg(db->dev, "ID %02x => defaulting to DM9000E\n", id_val);
181         db->type = TYPE_DM9000E;
182     }
183 
184     /* dm9000a/b are capable of hardware checksum offload */
185     if (db->type == TYPE_DM9000A || db->type == TYPE_DM9000B) {
186         db->can_csum = 1;
187         db->rx_csum = 1;
188         ndev->features |= NETIF_F_IP_CSUM;
189     }
190 
191     /* from this point we assume that we have found a DM9000 */
192 
193     /* driver system function */ //初始化以太网设备的公有成员
194     ether_setup(ndev);//在调用register_netdev之前必须初始化完全。该函数中为net_device设置了很多默认值
195 
196     ndev->netdev_ops    = &dm9000_netdev_ops;
197     ndev->watchdog_timeo    = msecs_to_jiffies(watchdog);
198     ndev->ethtool_ops    = &dm9000_ethtool_ops;
199 
200     db->msg_enable = NETIF_MSG_LINK;
201     db->mii.phy_id_mask = 0x1f;
202     db->mii.reg_num_mask = 0x1f;
203     db->mii.force_media = 0;
204     db->mii.full_duplex = 0;
205     db->mii.dev     = ndev;
206     db->mii.mdio_read = dm9000_phy_read;
207     db->mii.mdio_write = dm9000_phy_write;
208 
209     mac_src = "eeprom";
210 
211     /* try reading the node address from the attached EEPROM */
212     for (i = 0; i < 6; i += 2)
213         dm9000_read_eeprom(db, i / 2, ndev->dev_addr+i);
214 
215     if (!is_valid_ether_addr(ndev->dev_addr) && pdata != NULL) {
216         mac_src = "platform data";
217         memcpy(ndev->dev_addr, pdata->dev_addr, 6);
218     }
219 
220     if (!is_valid_ether_addr(ndev->dev_addr)) {
221         /* try reading from mac */
222         
223         mac_src = "chip";
224         for (i = 0; i < 6; i++)
225             ndev->dev_addr[i] = ior(db, i+DM9000_PAR);
226     }
227 
228     if (!is_valid_ether_addr(ndev->dev_addr))
229         dev_warn(db->dev, "%s: Invalid ethernet MAC address. Please "
230              "set using ifconfig\n", ndev->name);
231 
232     platform_set_drvdata(pdev, ndev);
233     ret = register_netdev(ndev); //注册net_device结构体
234 
235     if (ret == 0)
236         printk(KERN_INFO "%s: dm9000%c at %p,%p IRQ %d MAC: %pM (%s)\n",
237          ndev->name, dm9000_type_to_char(db->type),
238          db->io_addr, db->io_data, ndev->irq,
239          ndev->dev_addr, mac_src);
240     return 0;
241 
242 out:
243     dev_err(db->dev, "not found (%d).\n", ret);
244 
245     dm9000_release_board(pdev, db);
246     free_netdev(ndev); //分配错误则释放net_device结构
247 
248     return ret;
249 }
模块加载后转入probe中执行,在probe中完成了分配net_device、网络设备的初始化,设备驱动的加载。
先是分配获得了net_device结构体等。
网络设备初始化包括:
进行硬件上的准备工作,检查网络设备是否存在,检测所使用的硬件资源。主要是resource
获得软件接口上的准备工作。
获得私有数据指针,初始化以太网设备公有成员、初始化成员,初始化自旋锁或并发同步机制、申请设备所需的硬件资源 request_region等。
 
在网络设备驱动程序完成模块注册时,会调用dm9000_probe()函数进行初始化,分配并初始化net_device结构体。其中有些成员在dm9000_probe()中已经完成初始化,还有一些函数指针例如(*open)()、(*release)()等函数,也是在驱动程序中进行定义。
 
4.dm9000_open()
open函数在执行ifconfig命令时会被激活。主要作用是打开网络设备,获得设备所需的IO地址,IRQ、DMA通道等。 注册中断、设置寄存器、启动发送队列。
在字符设备驱动中是把中断注册放在模块初始化函数中,而网卡驱动则放在open函数中。原因是网卡有禁用操作,当被禁用的时候,要把占用的中断号释放。
 1 m9000_open(struct net_device *dev)
 2 {
 3     board_info_t *db = netdev_priv(dev);//获取设备私有数据 返回board_info_t的地址
 4     unsigned long irqflags = db->irq_res->flags & IRQF_TRIGGER_MASK;
 5 
 6     if (netif_msg_ifup(db))
 7         dev_dbg(db->dev, "enabling %s\n", dev->name);
 8 
 9     /* If there is no IRQ type specified, default to something that
10      * may work, and tell the user that this is a problem */
11 
12     if (irqflags == IRQF_TRIGGER_NONE)
13         dev_warn(db->dev, "WARNING: no IRQ resource flags set.\n");
14 
15     irqflags |= IRQF_SHARED;
16 //注册中断
17     if (request_irq(dev->irq, dm9000_interrupt, irqflags, dev->name, dev))
18         return -EAGAIN;
19 
20     /* Initialize DM9000 board */
21     dm9000_reset(db); //复位DM9000
22     dm9000_init_dm9000(dev); //初始化dm9000中net_device结构中的成员
23 
24     /* Init driver variable */
25     db->dbug_cnt = 0;
26 
27     mii_check_media(&db->mii, netif_msg_link(db), 1);//检测mii接口状态
28     netif_start_queue(dev); //启动发送队列  协议栈向网卡发送
29     
30     dm9000_schedule_poll(db);
31 
32     return 0;
33 }
5.stop()
设备关闭函数
tatic int dm9000_stop(struct net_device *ndev)
{
    board_info_t *db = netdev_priv(ndev);

    if (netif_msg_ifdown(db))
        dev_dbg(db->dev, "shutting down %s\n", ndev->name);

    cancel_delayed_work_sync(&db->phy_poll); /* 终止phy_poll队列中被延迟的任务 */

    netif_stop_queue(ndev); /* 关闭发送队列 */
    netif_carrier_off(ndev); 

    /* free interrupt */
    free_irq(ndev->irq, ndev);   /* 释放中断 */

    dm9000_shutdown(ndev);  /* 关闭DM9000网卡 */ 

    return 0;
}
6.dm9000_shutdown()
下面是调用的dm9000_shutdown(ndev)函数,该函数的功能是复位phy,配置寄存器GPR位0为1,关闭dm9000电源,配置寄存器IMR位7为1,disable中断,配置寄存器RCR,disable接收.
 1 static void dm9000_shutdown(struct net_device *dev)
 2 {
 3     board_info_t *db = netdev_priv(dev);
 4 
 5     /* RESET device */
 6     dm9000_phy_write(dev, 0, MII_BMCR, BMCR_RESET);   /* PHY RESET ,复位PHY*/ 
 7     iow(db, DM9000_GPR, 0x01);    /* Power-Down PHY */
 8     iow(db, DM9000_IMR, IMR_PAR);  /* Disable all interrupt ,关闭所有的中断*/
 9     iow(db, DM9000_RCR, 0x00);   /* Disable RX ,不再接受数据*/
10 }
7.数据发送函数
数据包发送流程:
1)设备驱动程序从上层协议传递过来的sk_buff参数获得数据包的有效数据和长度,将有效数据放入临时缓冲区中。
2)设置硬件寄存器,驱动网络设备进行数据发送操作。
 1 static int dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
 2 {
 3     unsigned long flags;
 4     board_info_t *db = netdev_priv(dev);
 5 
 6     dm9000_dbg(db, 3, "%s:\n", __func__);
 7 
 8     if (db->tx_pkt_cnt > 1)
 9         return NETDEV_TX_BUSY;
10 
11     spin_lock_irqsave(&db->lock, flags); //获得自旋锁
12 
13     /* Move data to DM9000 TX RAM */
14     writeb(DM9000_MWCMD, db->io_addr); //根据 IO 操作模式(8-bit or 16-bit)来增加写指针 1 或 2
15 
16     (db->outblk)(db->io_data, skb->data, skb->len); //将数据从sk_buff中copy到网卡的TX SRAM中
17     dev->stats.tx_bytes += skb->len; //统计发送的字节数
18 
19     db->tx_pkt_cnt++; //待发送计数 
20     /* TX control: First packet immediately send, second packet queue */
21     if (db->tx_pkt_cnt == 1) {  //如果计数为1,直接发送
22         dm9000_send_packet(dev, skb->ip_summed, skb->len);
23     } else {
24         /* Second packet */
25         db->queue_pkt_len = skb->len;
26         db->queue_ip_summed = skb->ip_summed;
27         netif_stop_queue(dev); //告诉上层停止发送
28     }
29 
30     spin_unlock_irqrestore(&db->lock, flags);//解锁
31 
32     /* free this SKB */
33     dev_kfree_skb(skb); //释放SKB
34 
35     return NETDEV_TX_OK;
36 }

dm9000_start_xmit通过调用dm9000_send_packet来发送数据。

8.发送数据
dm9000_start_xmit函数中获得要发送的数据字节数,并调用dm9000_send_packet来发送数据。
 1 static void dm9000_send_packet(struct net_device *dev,
 2              int ip_summed,
 3              u16 pkt_len)
 4 {
 5     board_info_t *dm = to_dm9000_board(dev);
 6 
 7     /* The DM9000 is not smart enough to leave fragmented packets alone. */
 8     if (dm->ip_summed != ip_summed) {
 9         if (ip_summed == CHECKSUM_NONE)
10             iow(dm, DM9000_TCCR, 0);
11         else
12             iow(dm, DM9000_TCCR, TCCR_IP | TCCR_UDP | TCCR_TCP);
13         dm->ip_summed = ip_summed;
14     }
15 
16     /* Set TX length to DM9000 *///设置发送数据的长度到TXPLL\TXPLH中
17     iow(dm, DM9000_TXPLL, pkt_len);
18     iow(dm, DM9000_TXPLH, pkt_len >> 8);
19 
20     /* Issue TX polling command *///设置发送寄存器的发送控制位,启动发送数据
21     iow(dm, DM9000_TCR, TCR_TXREQ);    /* Cleared after TX complete */
22 }
9.发送超时函数
发送数据时并不一定会成功,系统会调用dm9000_timeout函数。当传输数据超时时,意味发送操作失败或硬件进入未知状态。在超时函数中会调用netif_wake_queue()函数来重新启动设备发送队列。
 1 static void dm9000_timeout(struct net_device *dev)
 2 {
 3     board_info_t *db = netdev_priv(dev);
 4     u8 reg_save;
 5     unsigned long flags;
 6 
 7     /* Save previous register address */
 8     reg_save = readb(db->io_addr);
 9     spin_lock_irqsave(&db->lock, flags);
10 
11     netif_stop_queue(dev);
12     dm9000_reset(db);
13     dm9000_init_dm9000(dev);
14     /* We can accept TX packets again */
15     dev->trans_start = jiffies; /* prevent tx timeout */
16     netif_wake_queue(dev); //重启发送队列
17 
18     /* Restore previous register address */
19     writeb(reg_save, db->io_addr);
20     spin_unlock_irqrestore(&db->lock, flags);
21 }
由此, netif_wake_queue()函数与netif_stop_queue()是数据发送流程中要调用的两个重要的函数,分别用于唤醒和阻止上层向下层传送数据包。原型定义于include/linux/netdevice.h中。
 
10.发送中断处理函数
当一个数据包发送完成后会产生一个中断,进入中断处理函数。
 1 static void dm9000_tx_done(struct net_device *dev, board_info_t *db)
 2 {
 3     int tx_status = ior(db, DM9000_NSR);    /* Got TX status */
 4 
 5     if (tx_status & (NSR_TX2END | NSR_TX1END)) { //检测一个数据包发送完毕
 6         /* One packet sent complete */
 7         db->tx_pkt_cnt--;  //待发送的数据包数减1
 8         dev->stats.tx_packets++;//已发送数据包加1
 9 
10         if (netif_msg_tx_done(db))
11             dev_dbg(db->dev, "tx done, NSR %02x\n", tx_status);
12 
13         /* Queue packet check & send */
14         if (db->tx_pkt_cnt > 0) //如果还有数据包,则继续发送
15             dm9000_send_packet(dev, db->queue_ip_summed,
16                      db->queue_pkt_len);
17         netif_wake_queue(dev); //启动发送队列
18     }
19 }

11.中断处理函数

网络设备接收数据的主要方法是有中断引发设备的中断处理函数,中断处理函数判断中断的类型,如果为接收中断,则读取接收到的数据,分配sk_buff数据结构和数据缓冲区,将接收到的数据复制到数据缓冲区中,并调用netif_rx()函数将sk_buff传递给上层协议。
 1 static irqreturn_t dm9000_interrupt(int irq, void *dev_id)
 2 {
 3     struct net_device *dev = dev_id;
 4     board_info_t *db = netdev_priv(dev);
 5     int int_status;
 6     unsigned long flags;
 7     u8 reg_save;
 8 
 9     dm9000_dbg(db, 3, "entering %s\n", __func__);
10 
11     /* A real interrupt coming */
12 
13     /* holders of db->lock must always block IRQs */
14     spin_lock_irqsave(&db->lock, flags);
15 
16     /* Save previous register address */
17     reg_save = readb(db->io_addr);
18 
19     /* Disable all interrupts */
20     iow(db, DM9000_IMR, IMR_PAR);
21 
22     /* Got DM9000 interrupt status */ //获取中断类型
23     int_status = ior(db, DM9000_ISR);    /* Got ISR */
24     iow(db, DM9000_ISR, int_status);    /* Clear ISR status */
25 
26     if (netif_msg_intr(db))
27         dev_dbg(db->dev, "interrupt status %02x\n", int_status);
28 
29     /* Received the coming packet */ //接收到一个数据包
30     if (int_status & ISR_PRS)
31         dm9000_rx(dev); //调用数据接收函数
32 
33     /* Trnasmit Interrupt check */ //发送一个数据包
34     if (int_status & ISR_PTS)
35         dm9000_tx_done(dev, db); //调用数据发送函数
36 
37     if (db->type != TYPE_DM9000E) {
38         if (int_status & ISR_LNKCHNG) {
39             /* fire a link-change request */
40             schedule_delayed_work(&db->phy_poll, 1);
41         }
42     }
43 
44     /* Re-enable interrupt mask */
45     iow(db, DM9000_IMR, db->imr_all);
46 
47     /* Restore previous register address */
48     writeb(reg_save, db->io_addr);
49 
50     spin_unlock_irqrestore(&db->lock, flags);
51 
52     return IRQ_HANDLED;
53 }
12.接收数据
接收数据函数主要将接收到的数据包传递给上层。
  1 dm9000_rx(struct net_device *dev)
  2 {
  3     board_info_t *db = netdev_priv(dev); //获得网卡私有数据首地址
  4     struct dm9000_rxhdr rxhdr;
  5     struct sk_buff *skb;
  6     u8 rxbyte, *rdptr;
  7     bool GoodPacket;
  8     int RxLen;
  9 
 10     /* Check packet ready or not */
 11     do {//存储器地址不变的读数据
 12         ior(db, DM9000_MRCMDX);    /* Dummy read */ //MRCMDX是内存数据预取读命令
 13  
 14         /* Get most updated data */
 15         rxbyte = readb(db->io_data);
 16 
 17         /* Status check: this byte must be 0 or 1 */ //0、1为正确,2表示接收出错
 18         if (rxbyte & DM9000_PKT_ERR) {
 19             dev_warn(db->dev, "status check fail: %d\n", rxbyte);
 20             iow(db, DM9000_RCR, 0x00);    /* Stop Device */ //关闭设备 并停止中断请求
 21             iow(db, DM9000_ISR, IMR_PAR);    /* Stop INT request */
 22             return;
 23         }
 24 
 25         if (!(rxbyte & DM9000_PKT_RDY)) // 0x01没准备好,直接返回
 26             return;
 27 
 28         /* A packet ready now & Get status/length */
 29         GoodPacket = true;
 30         writeb(DM9000_MRCMD, db->io_addr);
 31       //读取数据,从RX_SRAM读取到rxhdr中
 32         (db->inblk)(db->io_data, &rxhdr, sizeof(rxhdr)); 
 33 
 34         RxLen = le16_to_cpu(rxhdr.RxLen);
 35 
 36         if (netif_msg_rx_status(db))
 37             dev_dbg(db->dev, "RX: status %02x, length %04x\n",
 38                 rxhdr.RxStatus, RxLen);
 39 
 40         /* Packet Status check */ //检查包得完整性
 41         if (RxLen < 0x40) {
 42             GoodPacket = false;
 43             if (netif_msg_rx_err(db))
 44                 dev_dbg(db->dev, "RX: Bad Packet (runt)\n");
 45         }
 46 
 47         if (RxLen > DM9000_PKT_MAX) {
 48             dev_dbg(db->dev, "RST: RX Len:%x\n", RxLen);
 49         }
 50 
 51         /* rxhdr.RxStatus is identical to RSR register. */
 52         if (rxhdr.RxStatus & (RSR_FOE | RSR_CE | RSR_AE |
 53                  RSR_PLE | RSR_RWTO |
 54                  RSR_LCS | RSR_RF)) {
 55             GoodPacket = false;
 56             if (rxhdr.RxStatus & RSR_FOE) {
 57                 if (netif_msg_rx_err(db))
 58                     dev_dbg(db->dev, "fifo error\n");
 59                 dev->stats.rx_fifo_errors++;
 60             }
 61             if (rxhdr.RxStatus & RSR_CE) {
 62                 if (netif_msg_rx_err(db))
 63                     dev_dbg(db->dev, "crc error\n");
 64                 dev->stats.rx_crc_errors++;
 65             }
 66             if (rxhdr.RxStatus & RSR_RF) {
 67                 if (netif_msg_rx_err(db))
 68                     dev_dbg(db->dev, "length error\n");
 69                 dev->stats.rx_length_errors++;
 70             }
 71         }
 72 
 73         /* Move data from DM9000 */ //从DM9000获取数据
 74         if (GoodPacket && //分配SKB
 75          ((skb = dev_alloc_skb(RxLen + 4)) != NULL)) {  //+4是因为除了数据包前面还有空读一字节、读状态一字节、读长度低位和高位各一个字节  76             skb_reserve(skb, 2);  //定位data指针 DA(6)+SA(6)+type(2)+IP包+CFS(校验码4字节) IP包要求四字节对齐  77             rdptr = (u8 *) skb_put(skb, RxLen - 4);  //定位tail指针  -4是减去校验码  78 
 79             /* Read received packet from RX SRAM */
 80        //读取数据 从RX SRAM 到sk_buff中
 81             (db->inblk)(db->io_data, rdptr, RxLen);
 82             dev->stats.rx_bytes += RxLen;
 83 
 84             /* Pass to upper layer */ //获取上层协议类型
 85             skb->protocol = eth_type_trans(skb, dev);
 86             if (db->rx_csum) {
 87                 if ((((rxbyte & 0x1c) << 3) & rxbyte) == 0)
 88                     skb->ip_summed = CHECKSUM_UNNECESSARY;
 89                 else
 90                     skb->ip_summed = CHECKSUM_NONE;
 91             }
 92             netif_rx(skb); //把数据包交给上层
 93             dev->stats.rx_packets++;
 94 
 95         } else {
 96             /* need to dump the packet's data */
 97 
 98             (db->dumpblk)(db->io_data, RxLen);
 99         }
100     } while (rxbyte & DM9000_PKT_RDY);
101 }
可以看出接收数据主要包括:
判断为接收数据中断----dm9000_rx()完成更深入的数据包接收工作[获取数据包长度,分配sk_buff和数据段缓冲区,读取硬件接收的数据放入缓冲区中,解析上层协议类型,将数据包交给上层]