linux的串口驱动分析

1、串口驱动中的数据结构

• UART驱动程序结构：struct uart_driver  驱动

• UART端口结构： struct uart_port  串口

• UART相关操作函数结构: struct uart_ops   串口操作函数集

• UART状态结构： struct uart_state 串口状态

• UART信息结构: struct uart_info  串口信息

2、串口驱动程序-初始化

3、串口驱动分析-打开设备

static int s3c24xx_serial_startup(struct uart_port *port)
{
    struct s3c24xx_uart_port *ourport = to_ourport(port);
    int ret;

    dbg("s3c24xx_serial_startup: port=%p (%08lx,%p)
",
        port->mapbase, port->membase);

    rx_enabled(port) = 1;

    ret = request_irq(ourport->rx_irq, s3c24xx_serial_rx_chars, 0,
              s3c24xx_serial_portname(port), ourport);

    if (ret != 0) {
        printk(KERN_ERR "cannot get irq %d
", ourport->rx_irq);
        return ret;
    }

    ourport->rx_claimed = 1;

    dbg("requesting tx irq...
");

    tx_enabled(port) = 1;

    ret = request_irq(ourport->tx_irq, s3c24xx_serial_tx_chars, 0,
              s3c24xx_serial_portname(port), ourport);

    if (ret) {
        printk(KERN_ERR "cannot get irq %d
", ourport->tx_irq);
        goto err;
    }

    ourport->tx_claimed = 1;

    dbg("s3c24xx_serial_startup ok
");

    /* the port reset code should have done the correct
     * register setup for the port controls */

    return ret;

 err:
    s3c24xx_serial_shutdown(port);
    return ret;
}

3、串口驱动程序-数据发送

static void s3c24xx_serial_start_tx(struct uart_port *port)
{
    struct s3c24xx_uart_port *ourport = to_ourport(port);
    static int a =1;//temp
    if (port->line == 3) {
//        printk("485_start_tx
");

        if(a){
            s3c_gpio_cfgpin(S3C64XX_GPK(5), S3C_GPIO_SFN(1));
            a=0;
        }
        gpio_set_value(S3C64XX_GPK(5), 1);
    }
    if (!tx_enabled(port)) {
        if (port->flags & UPF_CONS_FLOW)
            s3c24xx_serial_rx_disable(port);

        enable_irq(ourport->tx_irq);
        tx_enabled(port) = 1;
    }
}

static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id)
{
    struct s3c24xx_uart_port *ourport = id;
    struct uart_port *port = &ourport->port;
    struct circ_buf *xmit = &port->state->xmit;
    int count = 256;

    if (port->x_char) {
        wr_regb(port, S3C2410_UTXH, port->x_char);
        port->icount.tx++;
        port->x_char = 0;
        goto out;
    }

    /* if there isn't anything more to transmit, or the uart is now
     * stopped, disable the uart and exit
    */

    if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
        s3c24xx_serial_stop_tx(port);
        goto out;
    }

    /* try and drain the buffer... */

    while (!uart_circ_empty(xmit) && count-- > 0) {
        if (rd_regl(port, S3C2410_UFSTAT) & ourport->info->tx_fifofull)
            break;

        wr_regb(port, S3C2410_UTXH, xmit->buf[xmit->tail]);
        xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
        port->icount.tx++;
    }

    if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
        uart_write_wakeup(port);

    if (uart_circ_empty(xmit))
        s3c24xx_serial_stop_tx(port);

 out:
    return IRQ_HANDLED;
}

4、串口驱动程序-数据接收

s3c24xx_serial_rx_chars(int irq, void *dev_id)
{
    struct s3c24xx_uart_port *ourport = dev_id;
    struct uart_port *port = &ourport->port;
    struct tty_struct *tty = port->state->port.tty;
    unsigned int ufcon, ch, flag, ufstat, uerstat;
    int max_count = 64;

    while (max_count-- > 0) {
        ufcon = rd_regl(port, S3C2410_UFCON);
        ufstat = rd_regl(port, S3C2410_UFSTAT);

        if (s3c24xx_serial_rx_fifocnt(ourport, ufstat) == 0)
            break;

        uerstat = rd_regl(port, S3C2410_UERSTAT);
        ch = rd_regb(port, S3C2410_URXH);

        if (port->flags & UPF_CONS_FLOW) {
            int txe = s3c24xx_serial_txempty_nofifo(port);

            if (rx_enabled(port)) {
                if (!txe) {
                    rx_enabled(port) = 0;
                    continue;
                }
            } else {
                if (txe) {
                    ufcon |= S3C2410_UFCON_RESETRX;
                    wr_regl(port, S3C2410_UFCON, ufcon);
                    rx_enabled(port) = 1;
                    goto out;
                }
                continue;
            }
        }

        /* insert the character into the buffer */

        flag = TTY_NORMAL;
        port->icount.rx++;

        if (unlikely(uerstat & S3C2410_UERSTAT_ANY)) {
            dbg("rxerr: port ch=0x%02x, rxs=0x%08x
",
                ch, uerstat);

            /* check for break */
            if (uerstat & S3C2410_UERSTAT_BREAK) {
                dbg("break!
");
                port->icount.brk++;
                if (uart_handle_break(port))
                    goto ignore_char;
            }

            if (uerstat & S3C2410_UERSTAT_FRAME)
                port->icount.frame++;
            if (uerstat & S3C2410_UERSTAT_OVERRUN)
                port->icount.overrun++;

            uerstat &= port->read_status_mask;

            if (uerstat & S3C2410_UERSTAT_BREAK)
                flag = TTY_BREAK;
            else if (uerstat & S3C2410_UERSTAT_PARITY)
                flag = TTY_PARITY;
            else if (uerstat & (S3C2410_UERSTAT_FRAME |
                        S3C2410_UERSTAT_OVERRUN))
                flag = TTY_FRAME;
        }

        if (uart_handle_sysrq_char(port, ch))
            goto ignore_char;

        uart_insert_char(port, uerstat, S3C2410_UERSTAT_OVERRUN,
                 ch, flag);

 ignore_char:
        continue;
    }
    tty_flip_buffer_push(tty);

 out:
    return IRQ_HANDLED;
}

附：linux系统中一般的流控技术