console=device, options
//device 指代的是终端设备
//options 指代对device 进行的设置，它取决于具体的设备驱动

struct tty driver { int magic; //表示给这个结构体的 “幻数 ”，设为TTY_DRIVER_MAGIC，在 alloc_tty_driver() 函数中被初始化。struct cdev cdev; /*    应的字符设备cdev */ struct module *owner;     /*这个驱动的模块拥有者 */ const char *driver name; const char *devfs name; const char *name;     /* 设备名 */ int name base; /* offset of printed name */ int major; /* 主设备号 */ int minor start; /* 开始次设备号 */ int minor num; /* 设备数量 */ int num; /* 被分配的设备数量 */ short type; /* tty驱动的类型 */ short subtype; /* tty 驱动的子类型 */ struct termios init termios; /* 初始线路设置 */ //init_termios 为初始线路设置，为一个termios 结构体，这个成员被用来提供一个线路设置集合。int flags; /* tty 驱动标志 */ int refcount; /*引用计数 （针 可加载的tty驱动） */ struct proc dir entry *proc entry; /* /proc 文件系统入口 */ struct tty driver *other; /* 仅 PTY 驱动有意义 */ ... /* 接口函数 */ int (*open)(struct tty struct *tty, struct file *filp); void (*close)(struct tty struct *tty, struct file *filp); int (*write)(struct tty struct *tty, const unsigned char *buf, int count); void (*put char)(struct tty struct *tty, unsigned char ch); void (*flush chars)(struct tty struct *tty); int (*write room)(struct tty struct *tty); int (*chars in buffer)(struct tty struct *tty); int (*ioctl)(struct tty struct *tty, struct file *file,unsigned int cmd,unsigned long arg); void (*set termios)(struct tty struct *tty, struct termios *old); void (*throttle)(struct tty struct *tty); void (*unthrottle)(struct tty struct *tty); void (*stop)(struct tty struct *tty); void (*start)(struct tty struct *tty); void (*hangup)(struct tty struct *tty); void (*break ctl)(struct tty struct *tty, int state); void (*flush buffer)(struct tty struct *tty); void (*set ldisc)(struct tty struct *tty); void (*wait until sent)(struct tty struct *tty, int timeout); void (*send xchar)(struct tty struct *tty, char ch); int (*read proc)(char *page, char **start, off t off, int count, int *eof,  void *data); int (*write proc)(struct file *file, const char        user *buffer, unsigned long count, void *data); int (*tiocmget)(struct tty struct *tty, struct file *file); int (*tiocmset)(struct tty struct *tty, struct file *file,unsigned int set, unsigned int clear); struct list head tty drivers; }; 

struct termios tty std termios = { _ .c iflag = ICRNL | IXON, /* 输入模式 */ _ .c oflag = OPOST | ONLCR, /* 输出模式 */ _ .c cflag = B38400 | CS8 | CREAD | HUPCL, /* 控制模式 */ _ .c lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN,  /* 本地模式 */ _          _ _ .c cc = INIT C CC  /* 控制字符，用来修改终端的特殊字符映射 */ };

//1 分配tty 驱动 struct tty driver *alloc tty driver(int lines); //  这个函数返回 tty_driver 指针，其参数为要分配的设备数量，line会被赋值给 tty_driver 的num 成员//2 注册tty 驱动 int tty register driver(struct tty driver *driver); //  注册tty 驱动成功时返回0，参数为由alloc_tty_driver ()分配的tty_driver 结构体指针//3 注销tty 驱动 int tty unregister driver(struct tty driver *driver);// 这个函数与tty_register_driver ()对应，tty 驱动最终会调用上述函数注销tty_driver//4 注册tty 设备 void tty register device (struct tty driver *driver, unsigned index,  struct device *device); // 仅有tty_driver 是不够的，驱动必须依附于设备，tty_register_device()函数用于注册关联于tty_driver 的设备，index 为设备的索引 （范围是0～driver->num ）//5 注销tty 设备 void tty unregister device (struct tty driver *driver,unsigned index); // 上述函数与tty_register_device()对应，用于注销tty 设备//6 设置tty 驱动操作 void     tty set operations(struct     tty driver     *driver,     struct tty operations *op); // 上述函数会将tty_operations  结构体中的函数指针复制到tty_driver 对应的函数指针

/* tty 驱动的模块加载函数 */ static int     init xxx init (void) { ... /* 分配tty driver 结构体 */ xxx tty driver = alloc tty driver(XXX PORTS); /* 初始化tty driver 结构体 */ xxx tty driver->owner = THIS MODULE; xxx tty driver->devfs name = "tts/"; xxx tty driver->name = "ttyS"; xxx tty driver->major = TTY MAJOR; xxx tty driver->minor start = 64; xxx tty driver->type = TTY DRIVER TYPE SERIAL; xxx tty driver->subtype = SERIAL TYPE NORMAL; xxx tty driver->init termios = tty std termios; xxx tty driver->init termios.c cflag = B9600 |CS8 |CREAD |HUPCL | CLOCAL; xxx tty driver->flags = TTY DRIVER REAL RAW; tty set operations(xxx tty driver, &xxx ops); ret = tty register driver(xxx tty driver); if (ret) { printk(KERN ERR "Couldn't register xxx serial driver\n"); put tty driver(xxx tty driver); return ret; } ... ret = request irq (...); /* 硬件资源申请 */ ... }

/* 设备 “私有”数据结构体 */ struct xxx tty { struct tty struct *tty; /* tty struct 指针 */ int open count; /* 打开次数 */ struct semaphore sem; /* 结构体锁定信号量 */ intxmit buf; /* 传输 冲区 */ ... } /* 打开函数 */ static int xxx open (struct tty struct *tty, struct file *file) { struct xxx tty *xxx; /* 分配xxx tty */ xxx = kmalloc(sizeof(*xxx), GFP KERNEL); if (!xxx) return  - ENOMEM; /* 初始化xxx tty 中的成员 */ init MUTEX (&xxx->sem); xxx->open count = 0; ... /* 使tty struct 中的driver data 指向xxx tty */ tty->driver data = xxx; xxx->tty = tty; ... return 0; }

static int xxx write (struct tty struct *tty, const unsigned char *buf, int count) { /* 获得tty 设备私有数据 */ struct xxx tty *xxx = (struct xxx tty*)tty->driver data; ... /* 开始发送 */ while (1) { local irq save (flags); c = min t (int, count, min (SERIAL XMIT SIZE - xxx->xmit cnt - 1, SERIAL XMIT SIZE - xxx->xmit head)); if (c <= 0) { local irq restore (flags); break; } //复制到发送 冲区 memcpy (xxx->xmit buf + xxx->xmit head, buf, c); xxx->xmit head = (xxx->xmit head + c) &(SERIAL XMIT SIZE - 1); xxx->xmit cnt += c; local irq restore (flags); buf += c; count -= c; total += c; } if (xxx->xmit cnt && !tty->stopped && !tty->hw stopped) { start xmit (xxx);//开始发送 } return total; //返回发送的字节数 }

int tty register driver (struct tty driver *driver) { ... if (!driver->put char)//没有定义put char()函数 driver->put char = tty default put char; ... } static void tty default put char(struct tty struct *tty, unsigned char ch) { tty->driver->write (tty, &ch, 1);//调用tty driver.write ()函数 }

for (i = 0; i < data size; ++i) { if (tty->flip .count >= TTY FLIPBUF SIZE) tty flip buffer push (tty);//数据填满向上层 “推”tty insert flip char(tty, data[i], TTY NORMAL);//把数据插入 冲区 } tty flip buffer push (tty);

int tcgetattr (int fd, struct termios *termios p); int tcsetattr (int fd, int optional actions, struct termios *termios p); 

void (*set termios)(struct tty struct *tty, struct termios *old);

static int xxx tiocmget (struct tty struct *tty, struct file *file) { struct xxx tty *info = tty->driver  data; unsigned int result = 0; unsigned int msr = info->msr; unsigned int mcr = info->mcr; result = ((mcr &MCR DTR) ? TIOCM DTR : 0) |  /* DTR 被设置 */ ((mcr &MCR RTS) ? TIOCM RTS : 0) | /* RTS 被设置 */ ((mcr &MCR LOOP) ? TIOCM LOOP : 0) | /* LOOP 被设置 */ ((msr &MSR CTS) ? TIOCM CTS : 0) | /* CTS 被设置 */ ((msr &MSR CD) ? TIOCM CAR : 0) | /* CD 被设置*/ ((msr &MSR RI) ? TIOCM RI : 0) | /* 振铃指示被设置 */ ((msr &MSR DSR) ? TIOCM DSR : 0); /* DSR 被设置 */ return result; }

static int xxx ioctl(struct tty struct *tty, struct file *filp, unsigned int cmd, unsigned long arg) { struct xxx tty *info = tty->driver data; ... /* 处理各种命令 */ switch (cmd) { case TIOCGSERIAL: ... case TIOCSSERIAL: ... case TIOCSERCONFIG: ... case TIOCMIWAIT: ... case TIOCGICOUNT: ... case TIOCSERGETLSR: ... } ... }