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分类: 嵌入式

2010-05-26 16:28:48

一、核心数据结构
串口驱动有3个核心数据结构,它们都定义在<#include linux/serial_core.h>
1、uart_driver
uart_driver包含了串口设备名、串口驱动名、主次设备号、串口控制台(可选)等信息,还封装了tty_driver(底层串口驱动无需关心tty_driver)。

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 */

    
/*
     * 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;
};

2、uart_port
uart_port用于描述串口端口的I/O端口或I/O内存地址、FIFO大小、端口类型、串口时钟等信息。实际上,一个uart_port实例对应一个串口设备

struct uart_port {
    spinlock_t             lock;           /* 串口端口锁 */
    unsigned int           iobase;         /* IO端口基地址 */
    unsigned char __iomem *membase;        /* IO内存基地址,经映射(如ioremap)后的IO内存虚拟基地址 */
    unsigned int           irq;            /* 中断号 */
    unsigned int           uartclk;        /* 串口时钟 */
    unsigned int           fifosize;       /* 串口FIFO缓冲大小 */
    unsigned char          x_char;         /* xon/xoff字符 */
    unsigned char          regshift;       /* 寄存器位移 */
    unsigned char          iotype;         /* IO访问方式 */
    unsigned char          unused1;

#define UPIO_PORT        (0)               /* IO端口 */
#define UPIO_HUB6        (1)
#define UPIO_MEM         (2)               /* IO内存 */
#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;  /* 关心的Rx error status */
    unsigned int        ignore_status_mask;/* 忽略的Rx error status */
    struct uart_info      *info;           /* pointer to parent info */
    struct uart_icount     icount;         /* 计数器 */

    struct console        *cons;           /* console结构体 */
#ifdef CONFIG_SERIAL_CORE_CONSOLE
    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_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))
#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;        /* 当前的moden设置 */
    unsigned int             timeout;      /* character-based timeout */        
    unsigned int             type;         /* 端口类型 */
    const struct uart_ops   *ops;          /* 串口端口操作函数集 */
    unsigned int             custom_divisor;
    unsigned int             line;         /* 端口索引 */
    resource_size_t          mapbase;      /* IO内存物理基地址,可用于ioremap */
    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; /* 端口私有数据,一般为platform数据指针 */
};

uart_iconut为串口信息计数器,包含了发送字符计数、接收字符计数等。在串口的发送中断处理函数和接收中断处理函数中,我们需要管理这些计数。

struct uart_icount {
    __u32    cts;
    __u32    dsr;
    __u32    rng;
    __u32    dcd;
    __u32    rx
;      /* 发送字符计数 */
    __u32    tx;      /* 接受字符计数 */
    __u32    frame;   /* 帧错误计数 */
    __u32    overrun; /* Rx FIFO溢出计数 */
    __u32    parity /* 帧校验错误计数 */
    __u32    brk;     /* break计数 */
    __u32    buf_overrun;
};

uart_info有两个成员在底层串口驱动会用到:xmit和tty。用户空间程序通过串口发送数据时,上层驱动将用户数据保存在xmit;而串口发送中断处理函数就是通过xmit获取到用户数据并将它们发送出去。串口接收中断处理函数需要通过tty将接收到的数据传递给行规则层。

/* uart_info实例仅在串口端口打开时有效,它可能在串口关闭时被串口核心层释放。因此,在使用uart_port的uart_info成员时必须保证串口已打开。底层驱动和核心层驱动都可以修改uart_info实例。
 * This is the state information which is only valid when the port
 * is open; it may be freed by the core driver once the device has
 * been closed. Either the low level driver or the core can modify
 * stuff here.
 */

struct uart_info {
    struct tty_struct     *tty;
    struct circ_buf        xmit;
    uif_t                  flags;

/*
 * Definitions for info->flags. These are _private_ to serial_core, and
 * are specific to this structure. They may be queried by low level drivers.
 */

#define UIF_CHECK_CD        ((__force uif_t) (1 << 25))
#define UIF_CTS_FLOW        ((__force uif_t) (1 << 26))
#define UIF_NORMAL_ACTIVE    ((__force uif_t) (1 << 29))
#define UIF_INITIALIZED        ((__force uif_t) (1 << 31))
#define UIF_SUSPENDED        ((__force uif_t) (1 << 30))

    int                     blocked_open;

    struct tasklet_struct   tlet;

    wait_queue_head_t       open_wait;
    wait_queue_head_t       delta_msr_wait;
};

3、uart_ops

uart_ops涵盖了串口驱动可对串口设备进行的所有操作。

/*
 * This structure describes all the operations that can be
 * done on the physical hardware.
 */

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         (*set_termios)(struct uart_port *, struct ktermios *new, struct ktermios *old); /* 设置串口参数 */
    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); /*  */
    const char  *(*type)(struct uart_port *); /* 返回一描述串口类型的字符串 */
    void         (*release_port)(struct uart_port *); /* 释放串口