dm9000网卡驱动分析4

5102阅读　0评论2012-04-22　zhongli_i
分类：LINUX

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。

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  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;

  9.     dm9000_dbg(db, 3, "entering %s\n", __func__);

  11.     /* A real interrupt coming */

  13.     /* holders of db->lock must always block IRQs */
  14.     spin_lock_irqsave(&db->lock, flags);

  16.     /* Save previous register address */
  17.     reg_save = readb(db->io_addr);

  19.     /* Disable all interrupts */
  20.     iow(db, DM9000_IMR, IMR_PAR);

  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 */

  26.     if (netif_msg_intr(db))
  27.         dev_dbg(db->dev, "interrupt status %02x\n", int_status);

  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

  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

  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.     }

  44.     /* Re-enable interrupt mask */
  45.     iow(db, DM9000_IMR, db->imr_all);

  47.     /* Restore previous register address */
  48.     writeb(reg_save, db->io_addr);

  50.     spin_unlock_irqrestore(&db->lock, flags);

  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。

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  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;

  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);

  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.         }

  25.         if (!(rxbyte & DM9000_PKT_RDY)) // 0x01没准备好，直接返回
  26.             return;

  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)); 

  34.         RxLen = le16_to_cpu(rxhdr.RxLen);

  36.         if (netif_msg_rx_status(db))
  37.             dev_dbg(db->dev, "RX: status %02x, length %04x\n",
  38.                 rxhdr.RxStatus, RxLen);

  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.         }

  47.         if (RxLen > DM9000_PKT_MAX) {
  48.             dev_dbg(db->dev, "RST: RX Len:%x\n", RxLen);
  49.         }

  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.         }

  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)) {
  76.             skb_reserve(skb, 2);
  77.             rdptr = (u8 *) skb_put(skb, RxLen - 4);

  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;

  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++;

  95.         } else {
  96.             /* need to dump the packet's data */

  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]

更多细节参考
http://blog.csdn.net/yming0221/article/details/6628624
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