前面分析了dm9000a网卡的probe部分，接下来继续其他部分。
当用户在命令行下使用ifconfig等命令的时候，网卡设备将打开，系统将调用open函数。dm9000a的open函数如下
static int dmfe_open(struct net_device *dev)
{
board_info_t *db = (board_info_t *)dev->priv;
u8 reg_nsr;
int i;
if (request_irq(dev->irq,&dmfe_interrupt,IRQF_SHARED,dev->name,dev))
return -EAGAIN;
/* Grab the IRQ */
set_irq_type(dev->irq, IRQ_TYPE_EDGE_RISING);
/* Initilize DM910X board */
dmfe_init_dm9000(dev);
/* Init driver variable */
db->reset_counter = 0;
db->reset_tx_timeout = 0;
db->cont_rx_pkt_cnt = 0;
/* check link state and media speed */
db->Speed =10;
i=0;
do {
reg_nsr = ior(db,0x1);
if(reg_nsr & 0x40) /* link OK!! */
{
/* wait for detected Speed */
mdelay(200);
reg_nsr = ior(db,0x1);
if(reg_nsr & 0x80)
db->Speed =10;
else
db->Speed =100;
break;
}
i++;
mdelay(1);
}while(i3000); /* wait 3 second */
//printk("i=%d Speed=%d\n",i,db->Speed);
/* set and active a timer process */
init_timer(&db->timer);
db->timer.expires = DMFE_TIMER_WUT * 2;
db->timer.data = (unsigned long)dev;
db->timer.function = &dmfe_timer;
add_timer(&db->timer); //Move to DM9000 initiallization was finished.
netif_start_queue(dev);
return 0;
}
函数首先向系统申请中断，利用内核提供的request_irq函数。该函数声明于include/linux/interrupt.h中，而它的定于位于kernel/irq/manage.c中。关于它的说明和原型如下
/**
* request_irq - allocate an interrupt line
* @irq: Interrupt line to allocate
* @handler: Function to be called when the IRQ occurs
* @irqflags: Interrupt type flags
* @devname: An ascii name for the claiming device
* @dev_id: A cookie passed back to the handler function
*
* This call allocates interrupt resources and enables the
* interrupt line and IRQ handling. From the point this
* call is made your handler function may be invoked. Since
* your handler function must clear any interrupt the board
* raises, you must take care both to initialise your hardware
* and to set up the interrupt handler in the right order.
*
* Dev_id must be globally unique. Normally the address of the
* device data structure is used as the cookie. Since the handler
* receives this value it makes sense to use it.
*
* If your interrupt is shared you must pass a non NULL dev_id
* as this is required when freeing the interrupt.
*
* Flags:
*
* IRQF_SHARED Interrupt is shared
* IRQF_DISABLED Disable local interrupts while processing
* IRQF_SAMPLE_RANDOM The interrupt can be used for entropy
*
*/
int request_irq(unsigned int irq, irq_handler_t handler,
unsigned long irqflags, const char *devname, void *dev_id)
可见，传递给该函数的第一个参数是申请的中断号；第二个参数是一个函数指针，当发生相应的中断时，系统将调用该函数处理中断；第三个参数是中断的标志，可以是它说明文档中提到的三种中的任何一种，我们用的是IRQF_SHARED，表示中断可以共享；第四个参数就是设备的简称，可以在/proc/interrupts列表中找到。
申请完成中断后，驱动程序设置了中断的类型，使用set_irq_type函数。该函数声明于include/linux/interrupt.h，而定义于kernel/irq/chip.c，原型如下
/**
* set_irq_type - set the irq type for an irq
* @irq: irq number
* @type: interrupt type - see include/linux/interrupt.h
*/
int set_irq_type(unsigned int irq, unsigned int type)
第一个参数是中断号，第二歌参数是中断类型，表示上升沿触发、下降沿触发、高电平触发或者低电平触发。我们使用的是IRQ_TYPE_EDGE_RISING，即上升沿触发。
中断设置完成后，驱动程序需要对dm9000a芯片进行初始化，调用dmfe_init_dm9000函数，如下
static void dmfe_init_dm9000(struct net_device *dev)
{
board_info_t *db = (board_info_t *)dev->priv;
/* set the internal PHY power-on, GPIOs normal, and wait 2ms */
iow(db, DM9KS_GPR, 1); /* Power-Down PHY */
udelay(500);
iow(db, DM9KS_GPR, 0); /* GPR (reg_1Fh)bit GPIO0=0 pre-activate PHY */
udelay(20); /* wait 2ms for PHY power-on ready */
/* do a software reset and wait 20us */
iow(db, DM9KS_NCR, 3);
udelay(20); /* wait 20us at least for software reset ok */
iow(db, DM9KS_NCR, 3); /* NCR (reg_00h) bit[0] RST=1 & Loopback=1, reset on */
udelay(20); /* wait 20us at least for software reset ok */
/* I/O mode */
db->io_mode = ior(db, DM9KS_ISR) >> 6; /* ISR bit7:6 keeps I/O mode */
/* Set PHY */
db->op_mode = media_mode;
set_PHY_mode(db);
/* Program operating register */
iow(db, DM9KS_NCR, 0);
iow(db, DM9KS_TCR, 0); /* TX Polling clear */
iow(db, DM9KS_BPTR, 0x3f); /* Less 3kb, 600us */
iow(db, DM9KS_SMCR, 0); /* Special Mode */
iow(db, DM9KS_NSR, 0x2c); /* clear TX status */
iow(db, DM9KS_ISR, 0x0f); /* Clear interrupt status */
/* Added by jackal at 03/29/2004 */
/* Set address filter table */
dm9000_hash_table(dev);
/* Activate DM9000A/DM9010 */
iow(db, DM9KS_RXCR, DM9KS_REG05 | 1); /* RX enable */
iow(db, DM9KS_IMR, DM9KS_REGFF); // Enable TX/RX interrupt mask
/* Init Driver variable */
db->tx_pkt_cnt = 0;
netif_carrier_on(dev);
spin_lock_init(&db->lock);
}
该函数中使用了iow函数，看一看它的实现
static void iow(board_info_t *db, int reg, u8 value)
{
PUTB(reg, db->io_addr);
PUTB(value, db->io_data);
}
即将value写入reg表示的寄存器中。dmfe_init_dm9000函数的具体功能函数里面已经有注释，更详细的可以查看datasheet。dmfe_init_dm9000函数返回后，open函数还做了一些工作。首先，初始化一些设备变量
db->reset_counter = 0;
db->reset_tx_timeout = 0;
db->cont_rx_pkt_cnt = 0;
这些值在发送和接收数据的时候将会使用到，到讨论那些函数的时候将详细介绍。接下来，驱动程序需要为自己增加一个timer
init_timer(&db->timer);
db->timer.expires = DMFE_TIMER_WUT * 2;
db->timer.data = (unsigned long)dev;
db->timer.function = &dmfe_timer;
add_timer(&db->timer); //Move to DM9000 initiallization was finished.
timer的expires变量决定定时时间，当定时时间到的时候，就会执行function指定的函数。最后，使用add_timer()函数将初始化的timer插入挂起定时器全局队列。关于function指定的函数，将在后面说明。
最后，open函数调用netif_start_queue，该函数的定义位于include/linux/netdevice.h中
/**
* netif_start_queue - allow transmit
* @dev: network device
*
* Allow upper layers to call the device hard_start_xmit routine.
*/
static inline void netif_start_queue(struct net_device *dev)
{
clear_bit(__LINK_STATE_XOFF, &dev->state);
}
可见，该函数告诉系统可以使用hard_start_xmit进行数据发送了。
open函数到此就结束了。
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