开始接触时没弄清楚方向，把tty驱动全部浏览了一片，最后发现控制台驱动只和3个文件特别相关:
（1）s3c6400.c
（2）samsung.c
（3）serial_core.c
先说下这些文件的各自功能：
（1）看看这个文件的关键代码
static int __init s3c6400_serial_init(void)
{
return s3c24xx_serial_init(&s3c6400_serial_driver, &s3c6400_uart_inf);//samsung.c函数定义
}
static void __exit s3c6400_serial_exit(void)
{
platform_driver_unregister(&s3c6400_serial_driver);
}
module_init(s3c6400_serial_init);
module_exit(s3c6400_serial_exit);
这个C文件完成平台函数的卸载工作，并在
static struct platform_driver s3c6400_serial_driver = {
.probe = s3c6400_serial_probe,
.remove = __devexit_p(s3c24xx_serial_remove),
.driver = {
.name = "s3c6400-uart",
.owner = THIS_MODULE,
},
};声明平台操作函数。
由s3c6400_serial_init转向另一个文件samsung.c
由第一个C文件的s3c24xx_serial_init这个函数跳到第二个C文件的
int s3c24xx_serial_init(struct platform_driver *drv,
struct s3c24xx_uart_info *info)
{
dbg("s3c24xx_serial_init(%p,%p)\n", drv, info);
#ifdef CONFIG_PM
drv->suspend = s3c24xx_serial_suspend;
drv->resume = s3c24xx_serial_resume;
#endif
return platform_driver_register(drv);//平台驱动注册
}此时在第二个C完成两个重要的功能：
1：平台侦测函数
int s3c24xx_serial_probe(struct platform_device *dev,
struct s3c24xx_uart_info *info)
{
struct s3c24xx_uart_port *ourport;
int ret;
dbg("s3c24xx_serial_probe(%p, %p) %d\n", dev, info, probe_index);
ourport = &s3c24xx_serial_ports[probe_index];
probe_index++;
dbg("%s: initialising port %p...\n", __func__, ourport);
ret = s3c24xx_serial_init_port(ourport, info, dev);
if (ret < 0)
goto probe_err;
dbg("%s: adding port\n", __func__);
uart_add_one_port(&s3c24xx_uart_drv, &ourport->port);//添加串口端口，函数定义在串口核心层
platform_set_drvdata(dev, &ourport->port);
ret = device_create_file(&dev->dev, &dev_attr_clock_source);
if (ret < 0)
printk(KERN_ERR "%s: failed to add clksrc attr.\n", __func__);
ret = s3c24xx_serial_cpufreq_register(ourport);
if (ret < 0)
dev_err(&dev->dev, "failed to add cpufreq notifier\n");
return 0;
probe_err:
return ret;
}
uart_add_one_port（）我们继续追踪
int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)//添加一个端口
{
struct uart_state *state;
struct tty_port *port;
int ret = 0;
struct device *tty_dev;
BUG_ON(in_interrupt());
if (uport->line >= drv->nr)
return -EINVAL;
state = drv->state + uport->line;
port = &state->port;
mutex_lock(&port_mutex);
mutex_lock(&port->mutex);
if (state->uart_port) {
ret = -EINVAL;
goto out;
}
state->uart_port = uport;
state->pm_state = -1;
uport->cons = drv->cons;
uport->state = state;
/*
* If this port is a console, then the spinlock is already
* initialised.
*/
if (!(uart_console(uport) && (uport->cons->flags & CON_ENABLED))) {
spin_lock_init(&uport->lock);
lockdep_set_class(&uport->lock, &port_lock_key);
}
uart_configure_port(drv, state, uport);//配置端口
/*
* Register the port whether it's detected or not. This allows
* setserial to be used to alter this ports parameters.
*/
tty_dev = tty_register_device(drv->tty_driver, uport->line, uport->dev);//注册tty设备
if (likely(!IS_ERR(tty_dev))) {
device_init_wakeup(tty_dev, 1);
device_set_wakeup_enable(tty_dev, 0);
} else
printk(KERN_ERR "Cannot register tty device on line %d\n",
uport->line);
/*
* Ensure UPF_DEAD is not set.
*/
uport->flags &= ~UPF_DEAD;
out:
mutex_unlock(&port->mutex);
mutex_unlock(&port_mutex);
return ret;
}
（2）：在此C文件完成模块加载
static int __init s3c24xx_serial_modinit(void)//串口初始化
{
int ret;
ret = uart_register_driver(&s3c24xx_uart_drv);////注册uart驱动，在serial_core.c中实现
if (ret < 0) {
printk(KERN_ERR "failed to register UART driver\n");
return -1;
}
return 0;
}
module_init(s3c24xx_serial_modinit);
继续追踪串口驱动注册函数到第三个C文件：
int uart_register_driver(struct uart_driver *drv)//注册串口驱动
{
struct tty_driver *normal;
int i, retval;
BUG_ON(drv->state);
/*
* Maybe we should be using a slab cache for this, especially if
* we have a large number of ports to handle.
*/
drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL);
if (!drv->state)
goto out;
normal = alloc_tty_driver(drv->nr);
if (!normal)
goto out_kfree;
drv->tty_driver = normal;
normal->owner = drv->owner;
normal->driver_name = drv->driver_name;
normal->name = drv->dev_name;
normal->major = drv->major;
normal->minor_start = drv->minor;
normal->type = TTY_DRIVER_TYPE_SERIAL;
normal->subtype = SERIAL_TYPE_NORMAL;
normal->init_termios = tty_std_termios;
normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;
normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;
normal->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
normal->driver_state = drv;
tty_set_operations(normal, &uart_ops);
uart操作赋值给tty，定义在tty_io.c
/*
* Initialise the UART state(s).
*/
for (i = 0; i < drv->nr; i++) {
struct uart_state *state = drv->state + i;
struct tty_port *port = &state->port;
tty_port_init(port);//初始化tty端口，添加端口，在核心层的平台侦测函数里
port->ops = &uart_port_ops;
port->close_delay = 500; /* .5 seconds */
port->closing_wait = 30000; /* 30 seconds */
tasklet_init(&state->tlet, uart_tasklet_action,
(unsigned long)state);
}
retval = tty_register_driver(normal);//tty驱动注册
if (retval >= 0)
return retval;
put_tty_driver(normal);
out_kfree:
kfree(drv->state);
out:
return -ENOMEM;
}
由
在这一层实现最底层的数据收发功能
static int s3c24xx_serial_startup(struct uart_port *port)//申请中断资源，初始化底层驱动状态，并开启端口为可接收数据状态，并连接收发的中断服务函数
{
struct s3c24xx_uart_port *ourport = to_ourport(port);
int ret;
dbg("s3c24xx_serial_startup: port=%p (%08lx,%p)\n",
port->mapbase, port->membase);
rx_enabled(port) = 1;
ret = request_irq(ourport->rx_irq, s3c24xx_serial_rx_chars, 0,//申请中断资源
s3c24xx_serial_portname(port), ourport);
if (ret != 0) {
printk(KERN_ERR "cannot get irq %d\n", ourport->rx_irq);
return ret;
}
ourport->rx_claimed = 1;
dbg("requesting tx irq...\n");
tx_enabled(port) = 1;
ret = request_irq(ourport->tx_irq, s3c24xx_serial_tx_chars, 0,//申请中断资源
s3c24xx_serial_portname(port), ourport);
if (ret) {
printk(KERN_ERR "cannot get irq %d\n", ourport->tx_irq);
goto err;
}
ourport->tx_claimed = 1;
dbg("s3c24xx_serial_startup ok\n");
/* the port reset code should have done the correct
* register setup for the port controls */
return ret;
err:
s3c24xx_serial_shutdown(port);
return ret;
}
到目前为止完成了平台、TTY、uart驱动注册，第一次写有点乱。