终端设备驱动_结构体

终端设备驱动：

终端设备分类：串行端口终端(/dev/ttySn), 伪端口(/dev/pty), 控制台终端(/dev/ttyn, /dev/console)。

终端设备驱动结构：包含tty核心，tty线路规程（以特殊的方式格式化从一个用户或硬件收到到数据，ppp或bluetooth），tty驱动。

tty设备发送数据流程：tty核心从用户获取数据---->tty线程规程驱动----->tty驱动----->硬件。接收数据，相反。

struct tty_struct {
    int    magic;
    struct tty_driver    *driver;
    int    index;
    struct tty_ldisc     ldisc;
    struct mutex         termios_mutex;
    struct ktermios      *termios,
                         *termios_locked;
    char                 name[64];
    struct pid           *pgrp;
    struct pid           *session;
    unsigned long        flags;
    int                  count;
    struct winsize       winsize;
    unsigned char        stopped:1,
                         hw_stopped:1,
                         flow_stopped:1,
                         packet:1;
    unsigned char        low_latency:1,
                         warned:1;
    unsigned char        ctrl_status;
    unsigned int         receive_room;   /* Bytes free for queue */

    struct tty_struct    *link;
    struct fasync_struct *fasync;
    struct tty_bufhead   buf;
    int                  alt_speed;      /* For magic substitution of 38400 bps */
    wait_queue_head_t    write_wait;
    wait_queue_head_t    read_wait;
    struct work_struct   hangup_work;
    void                 *disc_data;
    void                 *driver_data;
    struct list_head     tty_files;

#define N_TTY_BUF_SIZE   4096

    /*
     * The following is data for the N_TTY line discipline. For
     * historical reasons, this is included in the tty structure.
     */
    unsigned int         column;
    unsigned char        lnext:1,
                         erasing:1,
                         raw:1,
                         real_raw:1,
                         icanon:1;
    unsigned char        closing:1;
    unsigned short       minimum_to_wake;
    unsigned long        overrun_time;
    int                  num_overrun;
    unsigned long        process_char_map[256/(8*sizeof(unsigned long))];
    char                 *read_buf;
    int                  read_head;
    int                  read_tail;
    int                  read_cnt;
    unsigned long        read_flags[N_TTY_BUF_SIZE/(8*sizeof(unsigned long))];
    int                  canon_data;
    unsigned long        canon_head;
    unsigned int         canon_column;
    struct mutex         atomic_read_lock;
    struct mutex         atomic_write_lock;
    unsigned char        *write_buf;
    int                  write_cnt;
    spinlock_t           read_lock;
    /* If the tty has a pending do_SAK, queue it here - akpm */
    struct work_struct   SAK_work;
};

tty设备驱动的主体工作是填充tty_driver结构体：

struct tty_driver {

int magic; /* magic number for this structure ，在alloc_tty_driver（）中被初始化*/

struct kref kref; /* Reference management */

struct cdev cdev; //对应到字符设备cdev

struct module *owner;

const char *driver_name;

const char *name; //设备名

int name_base; /* offset of printed name */

int major; /* major device number */

int minor_start; /* start of minor device number */

int minor_num; /* number of *possible* devices */

int num; /* number of devices allocated */

short type; /* type of tty driver */

short subtype; /* subtype of tty driver */

struct ktermios init_termios; /* Initial termios */

int flags; /* tty driver flags */

struct proc_dir_entry *proc_entry; /* /proc fs entry */

struct tty_driver *other; /* only used for the PTY driver */

/*

* Pointer to the tty data structures

*/

struct tty_struct **ttys;

struct ktermios **termios;

struct ktermios **termios_locked;

void *driver_state;

/*

* Driver methods

*/

const struct tty_operations *ops;

struct list_head tty_drivers;

};

tty_operations结构体：

struct tty_operations {

struct tty_struct * (*lookup)(struct tty_driver *driver,

struct inode *inode, int idx);

int  (*install)(struct tty_driver *driver, struct tty_struct *tty);

void (*remove)(struct tty_driver *driver, struct tty_struct *tty);

int  (*open)(struct tty_struct * tty, struct file * filp);

void (*close)(struct tty_struct * tty, struct file * filp);

void (*shutdown)(struct tty_struct *tty);

void (*cleanup)(struct tty_struct *tty);

int  (*write)(struct tty_struct * tty,

     const unsigned char *buf, int count);

int  (*put_char)(struct tty_struct *tty, unsigned char ch); //单个字节写函数

void (*flush_chars)(struct tty_struct *tty); //刷新数据到硬件

int  (*write_room)(struct tty_struct *tty); //指示有多少缓冲区空闲

int  (*chars_in_buffer)(struct tty_struct *tty); //指示缓冲区到长度

int  (*ioctl)(struct tty_struct *tty, struct file * file, //

   unsigned int cmd, unsigned long arg);

long (*compat_ioctl)(struct tty_struct *tty, struct file * file,

    unsigned int cmd, unsigned long arg);

void (*set_termios)(struct tty_struct *tty, struct ktermios * old);

void (*throttle)(struct tty_struct * tty); //tty核心输入缓冲满时调用

void (*unthrottle)(struct tty_struct * tty); //tty核心输入缓冲已被清空时调用

void (*stop)(struct tty_struct *tty); //停止tty驱动发数据给设备

void (*start)(struct tty_struct *tty); //恢复tty驱动发数据给设备

void (*hangup)(struct tty_struct *tty);

int (*break_ctl)(struct tty_struct *tty, int state);

void (*flush_buffer)(struct tty_struct *tty); //刷新缓冲区，丢弃剩下的数据

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 (*tiocmget)(struct tty_struct *tty, struct file *file);

int (*tiocmset)(struct tty_struct *tty, struct file *file,

unsigned int set, unsigned int clear);

int (*resize)(struct tty_struct *tty, struct winsize *ws);

int (*set_termiox)(struct tty_struct *tty, struct termiox *tnew);

int (*get_icount)(struct tty_struct *tty,

struct serial_icounter_struct *icount);

#ifdef CONFIG_CONSOLE_POLL

int (*poll_init)(struct tty_driver *driver, int line, char *options);

int (*poll_get_char)(struct tty_driver *driver, int line);

void (*poll_put_char)(struct tty_driver *driver, int line, char ch);

#endif

const struct file_operations *proc_fops;

};

1.分配tty驱动：

struct tty_driver *alloc_tty_driver(int lines);line为要分配到设备数量。

2.注册tty驱动：

int tty_register_driver(struct tty_driver *driver);

3.注销tty驱动：

int tty_unregister_driver(struct tty_driver *driver);

4.注册tty设备：

void tty_register_device(struct tty_driver *driver, unsigned index, struct device *device);用于注册关联于tty_driver的设备。

5.注销tty设备：

void tty_unregister_device(struct tty_driver *driver, unsigned index);

6.设置tty驱动操作：

void tty_set_operations(struct tty_driver *driver, struct tty_operations *op);

终端设备驱动应该包含：

1.模块加载和卸载函数：完成注册和注销tty_driver， 初始化和释放终端设备对应的tty_driver结构体成员及硬件资源。

2.实现tty_operations结构体中的函数：open, close, write,tiocmget, tiocmset等。

tty线路设置：

改变tty设备的线路设置或获取当前线路设置的两种方式：

1.调用用户空间的termios库函数。

 int tcgetattr(int fd, struct termios *termios_p); //获取终端设备的操作模式

 int tcsetattr(int fd, int optional_actions, struct termios *termios_p); //设置终端设备的操作模式

 输入/输出波特率的获取和设置：

  speed_t cfgetospeed(struct termios *termios_p); //获得输出波特率

  speed_t cfgetispeed(struct termios *termios_p); //获得输入波特率

  

  int cfsetospeed(struct termios *termios_p, speed_t speed); //设置输出波特率

  int cfsetispeed(struct termios *termios_p, speed_t speed); //设置输入波特率

线路控制函数:

  int tcdrain(int fd); //等待所有输出都被发送

  int tcflush(int fd, int queue_selector); //flush输入/输出缓存

  int tcflow(int fd, int action); //对输入和输出流进行控制

  int tcsendbreak(int fd, int duration); //发送break

2.对tty设备节点进行ioctl()调用

  termios库函数会被转化为对tty设备节点的ioctl()调用。

UART设备驱动：

linux内涵在serial_core.c文件中实现了UART设备的通用tty驱动层（串口核心层）。因此UART驱动的任务就变为实现serial_core.c中定义的一组uart_xxx接口。

串口核心层为串口设备驱动提供了3个结构体： uart_driver, uart_port, uart_ops。

struct uart_driver {

struct module *owner;

const char *driver_name;

const char *dev_name;

int major;

int minor;

int nr;

struct console *cons;

/*

* these are private; the low level driver should not

* touch these; they should be initialised to NULL

*/

struct uart_state *state;

struct tty_driver *tty_driver;

};

UART驱动注册/注销函数：

int uart_register_driver(struct uart_driver *drv);

void uart_unregister_driver(struct uart_driver *drv);

这两个函数的实现，包含了tty_register_driver()和tty_unregister_driver()。

struct uart_port {

spinlock_t lock; /* port lock */

unsigned long iobase; /* in/out[bwl] */IO端口基地址

unsigned char __iomem *membase; /* read/write[bwl] */IO内存基地址

unsigned int (*serial_in)(struct uart_port *, int);

void (*serial_out)(struct uart_port *, int, int);

unsigned int irq; /* irq number */

unsigned long irqflags; /* irq flags  */

unsigned int uartclk; /* base uart clock */

unsigned int fifosize; /* tx fifo size */

unsigned char x_char; /* xon/xoff char */

unsigned char regshift; /* reg offset shift */

unsigned char iotype; /* io access style */

unsigned char unused1;

#define UPIO_PORT (0)

#define UPIO_HUB6 (1)

#define UPIO_MEM (2)

#define UPIO_MEM32 (3)

#define UPIO_AU (4) /* Au1x00 type IO */

#define UPIO_TSI (5) /* Tsi108/109 type IO */

#define UPIO_DWAPB (6) /* DesignWare APB UART */

#define UPIO_RM9000 (7) /* RM9000 type IO */

unsigned int read_status_mask; /* driver specific */驱动特定的读状态掩码

unsigned int ignore_status_mask; /* driver specific */驱动特定的忽略状态掩码

struct uart_state *state; /* pointer to parent state */

struct uart_icount icount; /* statistics */

struct console *cons; /* struct console, if any */

#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)

unsigned long sysrq; /* sysrq timeout */

#endif

upf_t flags;

#define UPF_FOURPORT ((__force upf_t) (1 << 1))

#define UPF_SAK ((__force upf_t) (1 << 2))

#define UPF_SPD_MASK ((__force upf_t) (0x1030))

#define UPF_SPD_HI ((__force upf_t) (0x0010))

#define UPF_SPD_VHI ((__force upf_t) (0x0020))

#define UPF_SPD_CUST ((__force upf_t) (0x0030))

#define UPF_SPD_SHI ((__force upf_t) (0x1000))

#define UPF_SPD_WARP ((__force upf_t) (0x1010))

#define UPF_SKIP_TEST ((__force upf_t) (1 << 6))

#define UPF_AUTO_IRQ ((__force upf_t) (1 << 7))

#define UPF_HARDPPS_CD ((__force upf_t) (1 << 11))

#define UPF_LOW_LATENCY ((__force upf_t) (1 << 13))

#define UPF_BUGGY_UART ((__force upf_t) (1 << 14))

#define UPF_NO_TXEN_TEST ((__force upf_t) (1 << 15))

#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))

#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))

#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))

/* The exact UART type is known and should not be probed.  */

#define UPF_FIXED_TYPE ((__force upf_t) (1 << 27))

#define UPF_BOOT_AUTOCONF ((__force upf_t) (1 << 28))

#define UPF_FIXED_PORT ((__force upf_t) (1 << 29))

#define UPF_DEAD ((__force upf_t) (1 << 30))

#define UPF_IOREMAP ((__force upf_t) (1 << 31))

#define UPF_CHANGE_MASK ((__force upf_t) (0x17fff))

#define UPF_USR_MASK ((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))

unsigned int mctrl; /* current modem ctrl settings */

unsigned int timeout; /* character-based timeout */

unsigned int type; /* port type */

const struct uart_ops *ops;

unsigned int custom_divisor;

unsigned int line; /* port index */

resource_size_t mapbase; /* for ioremap */

struct device *dev; /* parent device */

unsigned char hub6; /* this should be in the 8250 driver */

unsigned char suspended;

unsigned char unused[2];

void *private_data; /* generic platform data pointer */

};

uart_port用于描述一个UART端口到IO端口或IO内存地址，FIFO大小，端口类型等信息。

添加/删除端口函数：

int uart_add_one_port(struct uart_driver *drv, struct uart_port *port);

int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port);

struct uart_ops {

unsigned int (*tx_empty)(struct uart_port *);

void (*set_mctrl)(struct uart_port *, unsigned int mctrl);

unsigned int (*get_mctrl)(struct uart_port *);

void (*stop_tx)(struct uart_port *);

void (*start_tx)(struct uart_port *);

void (*send_xchar)(struct uart_port *, char ch);

void (*stop_rx)(struct uart_port *);

void (*enable_ms)(struct uart_port *);

void (*break_ctl)(struct uart_port *, int ctl);

int (*startup)(struct uart_port *);

void (*shutdown)(struct uart_port *);

void (*flush_buffer)(struct uart_port *);

void (*set_termios)(struct uart_port *, struct ktermios *new,

      struct ktermios *old);

void (*set_ldisc)(struct uart_port *);

void (*pm)(struct uart_port *, unsigned int state,

     unsigned int oldstate);

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 *);

void (*config_port)(struct uart_port *, int);

int (*verify_port)(struct uart_port *, struct serial_struct *);

int (*ioctl)(struct uart_port *, unsigned int, unsigned long);

#ifdef CONFIG_CONSOLE_POLL

void (*poll_put_char)(struct uart_port *, unsigned char);

int (*poll_get_char)(struct uart_port *);

#endif

};

uart_ops定义了对UART的一系列操作，包括发送，接收及线路设置等。

struct tty_struct {
int
magic;
struct kref kref;
struct tty_driver *driver;
const struct tty_operations *ops;
int index;
/* The ldisc objects are protected by tty_ldisc_lock at the moment */
struct tty_ldisc ldisc; 与具体线程的关联在这
struct mutex termios_mutex;
spinlock_t ctrl_lock;
/* Termios values are protected by the termios mutex */
struct ktermios *termios, *termios_locked;
struct termiox *termiox;
/* May be NULL for unsupported */
char name[64];
struct pid *pgrp;
/* Protected by ctrl lock */
struct pid *session;
unsigned long flags;
int count;
struct winsize winsize;
/* termios mutex */
unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
unsigned char low_latency:1, warned:1;
unsigned char ctrl_status;
/* ctrl_lock */
unsigned int receive_room;
/* Bytes free for queue */

struct tty_struct *link;
struct fasync_struct *fasync;
struct tty_bufhead buf;
/* Locked internally */
int alt_speed;
/* For magic substitution of 38400 bps */
wait_queue_head_t write_wait;
wait_queue_head_t read_wait;
struct work_struct hangup_work;
void *disc_data;
void *driver_data;
struct list_head tty_files;


#define N_TTY_BUF_SIZE 4096


/*
* The following is data for the N_TTY line discipline.  For
* historical reasons, this is included in the tty structure.
* Mostly locked by the BKL.
*/
unsigned int column;
unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
unsigned char closing:1;
unsigned short minimum_to_wake;
unsigned long overrun_time;
int num_overrun;
unsigned long process_char_map[256/(8*sizeof(unsigned long))];
char *read_buf;
int read_head;
int read_tail;
int read_cnt;
unsigned long read_flags[N_TTY_BUF_SIZE/(8*sizeof(unsigned long))];
int canon_data;
unsigned long canon_head;
unsigned int canon_column;
struct mutex atomic_read_lock;
struct mutex atomic_write_lock;
unsigned char *write_buf;
int write_cnt;
spinlock_t read_lock;
/* If the tty has a pending do_SAK, queue it here - akpm */
struct work_struct SAK_work;
struct tty_port *port;
};