static struct uart_driver s3c24xx_uart_drv = {.owner = THIS_MODULE,.dev_name = "s3c2410_serial",.nr = CONFIG_SERIAL_SAMSUNG_UARTS,.cons = S3C24XX_SERIAL_CONSOLE,.driver_name = S3C24XX_SERIAL_NAME,.major = S3C24XX_SERIAL_MAJOR,.minor = S3C24XX_SERIAL_MINOR,
};
static int __init s3c24xx_serial_modinit(void)
{int ret;ret = uart_register_driver(&s3c24xx_uart_drv);if (ret < 0) {printk(KERN_ERR "failed to register UART drivern");return -1;}return 0;
}

struct uart_driver {struct module *owner; /* 拥有该uart_driver的模块,一般为THIS_MODULE */const char *driver_name; /* 串口驱动名，串口设备文件名以驱动名为基础 */const char *dev_name; /* 串口设备名 */int major; /* 主设备号 */int minor; /* 次设备号 */int nr; /* 该uart_driver支持的串口个数(最大) */struct console *cons; /* 其对应的console.若该uart_driver支持serial console,否则为NULL *//* 下面这俩，它们应该被初始化为NULL */struct uart_state *state; <span style="white-space:pre"> </span>/* 下层，串口驱动层 */struct tty_driver *tty_driver; /* tty相关 */
};

struct uart_state {struct tty_port port;int pm_state;struct circ_buf xmit;struct tasklet_struct tlet;struct uart_port *uart_port; // 对应于一个串口设备
};

 struct uart_port {spinlock_t lock; /* port lock */unsigned long iobase; /* io端口基地址（物理） */unsigned char __iomem *membase; /* io内存基地址（虚拟） */unsigned int (*serial_in)(struct uart_port *, int);void (*serial_out)(struct uart_port *, int, int);unsigned int irq; /* 中断号 */unsigned long irqflags; /* 中断标志 */unsigned int uartclk; /* 串口时钟 */unsigned int fifosize; /* 串口缓冲区大小 */unsigned char x_char; /* xon/xoff char */unsigned char regshift; /* 寄存器位移 */unsigned char iotype; /* IO访问方式 */unsigned char unused1;unsigned int read_status_mask; /* 关心 Rx error status */unsigned int ignore_status_mask; /* 忽略 Rx error status */struct uart_state *state; /* pointer to parent state */struct uart_icount icount; /* 串口信息计数器 */struct console *cons; /* struct console, if any */
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)unsigned long sysrq; /* sysrq timeout */
#endifupf_t flags;unsigned int mctrl; /* 当前的Moden 设置 */unsigned int timeout; /* character-based timeout */unsigned int type; /* 端口类型 */const struct uart_ops *ops; /* 串口端口操作函数 */unsigned int custom_divisor;unsigned int line; /* 端口索引 */resource_size_t mapbase; /* io内存物理基地址 */struct device *dev; /* 父设备 */unsigned char hub6; /* this should be in the 8250 driver */unsigned char suspended;unsigned char unused[2];void *private_data; /* generic platform data pointer */
};

 struct uart_ops {unsigned int (*tx_empty)(struct uart_port *); /* 串口的Tx FIFO缓存是否为空 */void (*set_mctrl)(struct uart_port *, unsigned int mctrl); /* 设置串口modem控制 */unsigned int (*get_mctrl)(struct uart_port *); /* 获取串口modem控制 */void (*stop_tx)(struct uart_port *); /* 禁止串口发送数据 */void (*start_tx)(struct uart_port *); /* 使能串口发送数据 */ void (*send_xchar)(struct uart_port *, char ch); /* 发送xChar */void (*stop_rx)(struct uart_port *); /* 禁止串口接收数据 */void (*enable_ms)(struct uart_port *); /* 使能modem的状态信号 */void (*break_ctl)(struct uart_port *, int ctl); /* 设置break信号 */int  (*startup)(struct uart_port *); /* 启动串口,应用程序打开串口设备文件时,该函数会被调用 */void (*shutdown)(struct uart_port *);/* 关闭串口,应用程序关闭串口设备文件时,该函数会被调用 */void (*flush_buffer)(struct uart_port *);void (*set_termios)(struct uart_port *, struct ktermios *new,struct ktermios *old); /* 设置串口参数 */void (*set_ldisc)(struct uart_port *);/* 设置线路规程 */void (*pm)(struct uart_port *, unsigned int state,unsigned int oldstate); /* 串口电源管理 */int (*set_wake)(struct uart_port *, unsigned int state);/** Return a string describing the type of the port*/const char *(*type)(struct uart_port *);/** Release IO and memory resources used by the port.* This includes iounmap if necessary.*/void (*release_port)(struct uart_port *);/** Request IO and memory resources used by the port.* This includes iomapping the port if necessary.*/int (*request_port)(struct uart_port *); /* 申请必要的IO端口/IO内存资源,必要时还可以重新映射串口端口 */void (*config_port)(struct uart_port *, int); /* 执行串口所需的自动配置 */int (*verify_port)(struct uart_port *, struct serial_struct *); /* 核实新串口的信息 */int (*ioctl)(struct uart_port *, unsigned int, unsigned long);
#ifdef CONFIG_CONSOLE_POLLvoid (*poll_put_char)(struct uart_port *, unsigned char);int (*poll_get_char)(struct uart_port *);
#endif
};

int uart_register_driver(struct uart_driver *drv)
{struct tty_driver *normal = NULL;int i, retval;/* 根据driver支持的最大设备数，申请n个 uart_state 空间，每一个 uart_state 都有一个uart_port */drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL);/* tty层：分配一个 tty_driver ，并将drv->tty_driver 指向它 */normal = alloc_tty_driver(drv->nr);drv->tty_driver = normal;/* 对 tty_driver 进行设置 */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);/** 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; /* driver->state->tty_port */tty_port_init(port);port->close_delay = 500; /* .5 seconds */port->closing_wait = 30000; /* 30 seconds *//* 初始化 tasklet */tasklet_init(&state->tlet, uart_tasklet_action,(unsigned long)state);}/* tty层：注册 driver->tty_driver */retval = tty_register_driver(normal);}

 static const struct tty_operations uart_ops = {.open = uart_open,.close = uart_close,.write = uart_write,.put_char = uart_put_char, // 单字节写函数.flush_chars = uart_flush_chars, // 刷新数据到硬件函数.write_room = uart_write_room, // 指示多少缓冲空闲的函数.chars_in_buffer= uart_chars_in_buffer, // 只是多少缓冲满的函数.flush_buffer = uart_flush_buffer, // 刷新数据到硬件.ioctl = uart_ioctl,.throttle = uart_throttle,.unthrottle = uart_unthrottle,.send_xchar = uart_send_xchar,.set_termios = uart_set_termios, // 当termios设置被改变时又tty核心调用.set_ldisc = uart_set_ldisc, // 设置线路规程函数.stop = uart_stop, .start = uart_start,.hangup = uart_hangup, // 挂起函数，当驱动挂起tty设备时调用.break_ctl = uart_break_ctl, // 线路中断控制函数.wait_until_sent= uart_wait_until_sent,
#ifdef CONFIG_PROC_FS.proc_fops = &uart_proc_fops,
#endif.tiocmget = uart_tiocmget, // 获得当前tty的线路规程的设置.tiocmset = uart_tiocmset, // 设置当前tty线路规程的设置
#ifdef CONFIG_CONSOLE_POLL.poll_init = uart_poll_init,.poll_get_char = uart_poll_get_char,.poll_put_char = uart_poll_put_char,
#endif
};

int tty_register_driver(struct tty_driver *driver)
{int error;int i;dev_t dev;void **p = NULL;if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM) && driver->num) {p = kzalloc(driver->num * 2 * sizeof(void *), GFP_KERNEL);}/* 如果没有主设备号则申请 */if (!driver->major) {error = alloc_chrdev_region(&dev, driver->minor_start,driver->num, driver->name);} else {dev = MKDEV(driver->major, driver->minor_start);error = register_chrdev_region(dev, driver->num, driver->name);}if (p) { /* 为线路规程和termios分配空间 */driver->ttys = (struct tty_struct **)p;driver->termios = (struct ktermios **)(p + driver->num);} else {driver->ttys = NULL;driver->termios = NULL;}/* 创建字符设备，使用 tty_fops */cdev_init(&driver->cdev, &tty_fops);driver->cdev.owner = driver->owner;error = cdev_add(&driver->cdev, dev, driver->num);mutex_lock(&tty_mutex);/* 将该 driver->tty_drivers 添加到全局链表 tty_drivers */list_add(&driver->tty_drivers, &tty_drivers);mutex_unlock(&tty_mutex);if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {for (i = 0; i < driver->num; i++)tty_register_device(driver, i, NULL);}/* proc 文件系统注册driver */proc_tty_register_driver(driver);driver->flags |= TTY_DRIVER_INSTALLED;return 0;
}

static int tty_open(struct inode *inode, struct file *filp)
{int ret;lock_kernel();ret = __tty_open(inode, filp);unlock_kernel();return ret;
}

static int __tty_open(struct inode *inode, struct file *filp)
{struct tty_struct *tty = NULL;int noctty, retval;struct tty_driver *driver;int index;dev_t device = inode->i_rdev;unsigned saved_flags = filp->f_flags;
//在全局tty_drivers链表中获取Core注册的tty_driverdriver = get_tty_driver(device, &index);tty = tty_init_dev(driver, index, 0); // tty->ops = driver->ops;filp->private_data = tty;if (tty->ops->open)/* 调用tty_driver->tty_foperation->open */retval = tty->ops->open(tty, filp);return 0;
}

struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx, int first_ok)
{struct tty_struct *tty;int retval;/* 分配一个 tty_struct */tty = alloc_tty_struct();/* 初始化 tty ，设置线路规程 Ops 等 */initialize_tty_struct(tty, driver, idx);//tty_ldisc_open(tty, ld)-> return ld->ops->open(tty) -> n_tty_openretval = tty_ldisc_setup(tty, tty->link); return tty;
}void initialize_tty_struct(struct tty_struct *tty,struct tty_driver *driver, int idx)
{memset(tty, 0, sizeof(struct tty_struct));/* 设置线路规程为 N_TTY */tty_ldisc_init(tty);//struct tty_ldisc *ld = tty_ldisc_get(N_TTY);tty_ldisc_assign(tty, ld);...tty_buffer_init(tty);tty->driver = driver;/* 初始化等待队列头 */init_waitqueue_head(&tty->write_wait);init_waitqueue_head(&tty->read_wait);/* 将driver->ops 拷贝到 tty->ops */tty->ops = driver->ops;tty->index = idx;
}void tty_buffer_init(struct tty_struct *tty)
{spin_lock_init(&tty->buf.lock);tty->buf.head = NULL;tty->buf.tail = NULL;tty->buf.free = NULL;tty->buf.memory_used = 0;/* 初始化延时工作队列 */INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
}
```

static int uart_open(struct tty_struct *tty, struct file *filp)
{struct uart_driver *drv = (struct uart_driver *)tty->driver->driver_state;struct uart_state *state;struct tty_port *port;int retval, line = tty->index;state = uart_get(drv, line);port = &state->port; tty->driver_data = state; state->uart_port->state = state;/* uport->ops->startup(uport) 调用到最底层的ops里的startup 函数*/retval = uart_startup(state, 0);}

static ssize_t tty_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{struct tty_struct *tty;struct inode *inode = file->f_path.dentry->d_inode;ssize_t ret;struct tty_ldisc *ld;tty = (struct tty_struct *)file->private_data;ld = tty_ldisc_ref_wait(tty);if (!ld->ops->write)ret = -EIO;else/* 调用 线路规程 n_tty_write 函数 */ret = do_tty_write(ld->ops->write, tty, file, buf, count);tty_ldisc_deref(ld);return ret;
}
static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,const unsigned char *buf, size_t nr)
{const unsigned char *b = buf;DECLARE_WAITQUEUE(wait, current);int c;ssize_t retval = 0;// 将当前进程添加到等待队列add_wait_queue(&tty->write_wait, &wait);while (1) {// 设置当前进程为可中断的set_current_state(TASK_INTERRUPTIBLE);if (signal_pending(current)) {retval = -ERESTARTSYS;break;}if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {retval = -EIO;break;}/* 自行定义了输出方式 */if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {....} else {while (nr > 0) {/* 调用到 uart_write */c = tty->ops->write(tty, b, nr);if (c < 0) {retval = c;goto break_out;}if (!c)break;b += c;nr -= c;}}if (!nr)break;if (file->f_flags & O_NONBLOCK) {retval = -EAGAIN;break;}// 进程调度 开始休眠schedule();}
}

static int uart_write(struct tty_struct *tty, const unsigned char *buf, int count)
{uart_start(tty);return ret;
}static void uart_start(struct tty_struct *tty)
{__uart_start(tty);
}static void __uart_start(struct tty_struct *tty)
{struct uart_state *state = tty->driver_data;struct uart_port *port = state->uart_port;if (!uart_circ_empty(&state->xmit) && state->xmit.buf &&!tty->stopped && !tty->hw_stopped)/* 调用到最底层的 start_tx */port->ops->start_tx(port);
}

static ssize_t tty_read(struct file *file, char __user *buf, size_t count,loff_t *ppos)
{int i;struct tty_struct *tty;struct inode *inode;struct tty_ldisc *ld;tty = (struct tty_struct *)file->private_data;inode = file->f_path.dentry->d_inode;ld = tty_ldisc_ref_wait(tty);/* 调用线路规程 n_tty_read */if (ld->ops->read)i = (ld->ops->read)(tty, file, buf, count);elsei = -EIO;tty_ldisc_deref(ld);if (i > 0)inode->i_atime = current_fs_time(inode->i_sb);return i;
}

static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,unsigned char __user *buf, size_t nr)
{unsigned char __user *b = buf;DECLARE_WAITQUEUE(wait, current);int c;int minimum, time;ssize_t retval = 0;ssize_t size;long timeout;unsigned long flags;int packet;do_it_again:BUG_ON(!tty->read_buf);c = job_control(tty, file);minimum = time = 0;timeout = MAX_SCHEDULE_TIMEOUT;/* 如果是非标准模式 */if (!tty->icanon) {...}packet = tty->packet;add_wait_queue(&tty->read_wait, &wait);while (nr) {/* First test for status change. */if (packet && tty->link->ctrl_status) {/* 看不懂的都删掉 */}/* This statement must be first before checking for inputso that any interrupt will set the state back toTASK_RUNNING. */set_current_state(TASK_INTERRUPTIBLE);if (((minimum - (b - buf)) < tty->minimum_to_wake) &&((minimum - (b - buf)) >= 1))tty->minimum_to_wake = (minimum - (b - buf));if (!input_available_p(tty, 0)) {/* 看不懂的都删掉 *//* FIXME: does n_tty_set_room need locking ? */n_tty_set_room(tty);/* 进程调度 休眠 */timeout = schedule_timeout(timeout);continue;}__set_current_state(TASK_RUNNING);/* Deal with packet mode. */if (packet && b == buf) {/* 看不懂的都删掉 */}/* 如果是标准模式 */if (tty->icanon) {/* N.B. avoid overrun if nr == 0 */while (nr && tty->read_cnt) {int eol;eol = test_and_clear_bit(tty->read_tail,tty->read_flags);/* 从tty->read_buf 获取数据 */c = tty->read_buf[tty->read_tail];spin_lock_irqsave(&tty->read_lock, flags);tty->read_tail = ((tty->read_tail+1) &(N_TTY_BUF_SIZE-1));tty->read_cnt--;if (eol) {/* this test should be redundant:* we shouldn't be reading data if* canon_data is 0*/if (--tty->canon_data < 0)tty->canon_data = 0;}spin_unlock_irqrestore(&tty->read_lock, flags);if (!eol || (c != __DISABLED_CHAR)) {/* 将数据拷贝到用户空间 */if (tty_put_user(tty, c, b++)) {retval = -EFAULT;b--;break;}nr--;}if (eol) {tty_audit_push(tty);break;}}if (retval)break;} else {/* 非标准模式不关心删掉 */}....}mutex_unlock(&tty->atomic_read_lock);remove_wait_queue(&tty->read_wait, &wait);if (!waitqueue_active(&tty->read_wait))tty->minimum_to_wake = minimum;__set_current_state(TASK_RUNNING);...n_tty_set_room(tty);return retval;
}

void tty_flip_buffer_push(struct tty_struct *tty)
{unsigned long flags;spin_lock_irqsave(&tty->buf.lock, flags);if (tty->buf.tail != NULL)tty->buf.tail->commit = tty->buf.tail->used;spin_unlock_irqrestore(&tty->buf.lock, flags);if (tty->low_latency)flush_to_ldisc(&tty->buf.work.work);elseschedule_delayed_work(&tty->buf.work, 1);
}