/*
 * This routine is called when an device driver (i.e. an
 * interface) is ready to transmit a packet.
 */
//该函数功能:遍历设备的缓冲队列，对所有的数据包调用dev_queue_xmit()函数发送数据
void dev_tint(struct device *dev)
{
 int i;
 struct sk_buff *skb;
 unsigned long flags;
 
 save_flags(flags); 
 /*
  * Work the queues in priority order
  */
 
 for(i = 0;i < DEV_NUMBUFFS; i++)
 {
  /*
   * Pull packets from the queue
   */
  

  cli();
  while((skb=skb_dequeue(&dev->buffs[i]))!=NULL)
  {
   /*
    * Stop anyone freeing the buffer while we retransmit it
    */
   skb_device_lock(skb);
   restore_flags(flags);
   /*
    * Feed them to the output stage and if it fails
    * indicate they re-queue at the front.
    */
   dev_queue_xmit(skb,dev,-i - 1);//注意优先级的计算方式，在函数dev_queue_xmit()中优先级若<0则计算pri=-pri-1=-(-i-1)-1=i，
             //这样做的目的就是为了得到正确的where值,函数(dev_queue_xmit())中
   /*
    * If we can take no more then stop here.
    */
   if (dev->tbusy)
    return;
   cli();
  }
 }
 restore_flags(flags);
}