linux内核uart驱动，使用队列解耦原有的功能函数

Linux内核UART驱动通常使用队列来解耦原有的功能函数，以提高代码的可读性和可维护性。这种方法的基本思想是将不同的功能分割成独立的模块，每个模块都有一个输入队列和一个输出队列。

输入队列用于接收来自UART接口的数据，处理数据并将结果放入输出队列中。输出队列中的数据可以是控制命令、状态信息或者其他需要传递给上层应用程序的数据。这种方法的优点是可以使编写驱动程序更加简单，易于维护和扩展。

以下是一个使用队列解耦原有功能函数的UART驱动程序的示例：

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/serial_core.h>

#define BUFFER_SIZE 1024

struct uart_device {
    struct cdev cdev;
    struct uart_port port;
    struct mutex mutex;
    struct work_struct work;
    struct tasklet_struct tasklet;
    spinlock_t lock;
    wait_queue_head_t read_queue;
    wait_queue_head_t write_queue;
    char *buf;
    int head;
    int tail;
};

static int uart_driver_open(struct inode *inode, struct file *file)
{
    struct uart_device *dev;

    dev = container_of(inode->i_cdev, struct uart_device, cdev);
    file->private_data = dev;

    return 0;
}

static int uart_driver_release(struct inode *inode, struct file *file)
{
    return 0;
}

static ssize_t uart_driver_read(struct file *file, char __user *buf, size_t count, loff_t *offset)
{
    struct uart_device *dev = file->private_data;
    ssize_t ret;

    if (count == 0)
        return 0;

    if (wait_event_interruptible(dev->read_queue, dev->head != dev->tail))
        return -ERESTARTSYS;

    mutex_lock(&dev->mutex);

    if (dev->head > dev->tail) {
        ret = min_t(ssize_t, count, dev->head - dev->tail);
        if (copy_to_user(buf, dev->buf + dev->tail, ret)) {
            ret = -EFAULT;
            goto out;
        }
        dev->tail += ret;
    } else {
        ret = min_t(ssize_t, count, BUFFER_SIZE - dev->tail);
        if (copy_to_user(buf, dev->buf + dev->tail, ret)) {
            ret = -EFAULT;
            goto out;
        }
        dev->tail = (dev->tail + ret) % BUFFER_SIZE;
    }

out:
    mutex_unlock(&dev->mutex);

    return ret;
}

static ssize_t uart_driver_write(struct file *file, const char __user *buf, size_t count, loff_t *offset)
{
    struct uart_device *dev = file->private_data;
    ssize_t ret;

    if (count == 0)
        return 0;

    if (wait_event_interruptible(dev->write_queue, dev->head != ((dev->tail - 1 + BUFFER_SIZE) % BUFFER_SIZE)))
        return -ERESTARTSYS;

    mutex_lock(&dev->mutex);

    if (dev->tail > dev->head) {
        ret = min_t(ssize_t, count, BUFFER_SIZE - dev->tail);
        if (copy_from_user(dev->buf + dev->tail, buf, ret)) {
            ret = -EFAULT;
            goto out;
        }
        dev->tail += ret;
    } else {
        ret = min_t(ssize_t, count, dev->head - dev->tail);
        if (copy_from_user(dev->buf + dev->tail, buf, ret)) {
            ret = -EFAULT;
            goto out;
        }
        dev->tail = (dev->tail + ret) % BUFFER_SIZE;
    }

out:
    mutex_unlock(&dev->mutex);

    return ret;
}

static void uart_driver_work(struct work_struct *work)
{
    struct uart_device *dev = container_of(work, struct uart_device, work);
    struct uart_port *port = &dev->port;
    unsigned char c;
    int i;

    mutex_lock(&dev->mutex);

    while (uart_chars_avail(port)) {
        c = uart_get_char(port);
        if (dev->head == ((dev->tail - 1 + BUFFER_SIZE) % BUFFER_SIZE)) {
            /* Buffer is full, drop the incoming character */
            continue;
        }
        dev->buf[dev->head] = c;
        dev->head = (dev->head + 1) % BUFFER_SIZE;
    }

    mutex_unlock(&dev->mutex);

    wake_up_interruptible(&dev->read_queue);
}

static void uart_driver_tasklet(unsigned long data)
{
    struct uart_device *dev = (struct uart_device *)data;
    struct uart_port *port = &dev->port;
    unsigned char c;
    int i;

    spin_lock(&dev->lock);

    while (uart_chars_avail(port)) {
        c = uart_get_char(port);
        if (dev->head == ((dev->tail - 1 + BUFFER_SIZE) % BUFFER_SIZE)) {
            /* Buffer is full, drop the incoming character */
            continue;
        }
        dev->buf[dev->head] = c;
        dev->head = (dev->head + 1) % BUFFER_SIZE;
    }

    spin_unlock(&dev->lock);

    wake_up_interruptible(&dev->read_queue);
}

static void uart_driver_start(struct uart_port *port)
{
    struct uart_device *dev = container_of(port, struct uart_device, port);

    INIT_WORK(&dev->work, uart_driver_work);
    tasklet_init(&dev->tasklet, uart_driver_tasklet, (unsigned long)dev);
    spin_lock_init(&dev->lock);
    init_waitqueue_head(&dev->read_queue);
    init_waitqueue_head(&dev->write_queue);
    mutex_init(&dev->mutex);

    dev->buf = kzalloc(BUFFER_SIZE, GFP_KERNEL);
    dev->head = 0;
    dev->tail = 0;

    uart_write_wakeup(port);
}

static void uart_driver_stop(struct uart_port *port)
{
    struct uart_device *dev = container_of(port, struct uart_device, port);

    cancel_work_sync(&dev->work);
    tasklet_kill(&dev->tasklet);
    spin_lock_irq(&dev->lock);
    dev->head = dev->tail = 0;
    spin_unlock_irq(&dev->lock);
    kfree(dev->buf);
}

static struct uart_ops uart_driver_ops = {
    .tx_empty = uart_tx_empty,
    .set_mctrl = uart_set_mctrl,
    .get_mctrl = uart_get_mctrl,
    .stop_tx = uart_stop_tx,
    .start_tx = uart_start_tx,
    .send_xchar = uart_send_xchar,
    .stop_rx = uart_stop_rx,
    .enable_ms = uart_enable_ms,
    .break_ctl = uart_break_ctl,
    .startup = uart_driver_start,
    .shutdown = uart_driver_stop,
};

static struct uart_driver uart_driver = {
    .owner = THIS_MODULE,
    .driver_name = "uart_driver",
    .dev_name = "ttyUART",
    .major = 0,
    .minor = 0,
    .nr = 1,
    .cons = NULL,
    .ops = &uart_driver_ops,
};

static int __init uart_driver_init(void)
{
    dev_t devno;
    int ret;

    ret = alloc_chrdev_region(&devno, 0, 1, "uart_driver");
    if (ret < 0)
        return ret;

    cdev_init(&uart_driver.cdev, &uart_driver_ops);
    uart_driver.cdev.owner = THIS_MODULE;

    ret = cdev_add(&uart_driver.cdev, devno, 1);
    if (ret < 0) {
        unregister_chrdev_region(devno, 1);
        return ret;
    }

    uart_register_driver(&uart_driver);

    return 0;
}

static void __exit uart_driver_exit(void)
{
    uart_unregister_driver(&uart_driver);
    cdev_del(&uart_driver.cdev);
    unregister_chrdev_region(uart_driver.cdev.dev, 1);
}

module_init(uart_driver_init);
module_exit(uart_driver_exit);

MODULE_AUTHOR("Your Name");
MODULE_LICENSE("GPL");

在这个驱动程序中，我们使用了两个输入队列和一个输出队列。`read_queue` 用于接收来自 UART 的数据，`write_queue` 用于接收要发送到 UART 的数据，`buf` 用于存储接收到的数据。

`wait_event_interruptible` 函数用于等待数据到达队列。`mutex_lock` 和 `mutex_unlock` 函数用于保护共享数据结构。`wake_up_interruptible` 函数用于唤醒等待在队列上的进程。

`uart_driver_work` 和 `uart_driver_tasklet` 函数用于从 UART 中接收数据，并将接收到的数据放入输入队列中。

`uart_driver_start` 和 `uart_driver_stop` 函数用于初始化和清除输入队列和输出队列中的数据。`uart_driver_ops` 结构体包含了驱动程序中使用的 UART 操作。`uart_driver` 结构体包含了驱动程序的基本信息。

通过使用队列解耦原有的功能函数，我们可以将驱动程序中的不同部分分割成独立的模块，使得代码更加简洁、易于维护和扩展。