imx6ull 内核 epit定时器字符驱动使用例程？

以下是一个简单的例程，用于使用imx6ull内核的epit定时器字符驱动：

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/uaccess.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/interrupt.h>

#define DEV_NAME "epit_timer"
#define EPIT_BASE_ADDR 0x020D0000
#define EPIT_IRQ_NUM 88

typedef struct {
    dev_t dev_num;
    struct cdev cdev;
    struct class *cls;
    struct device *dev;
    void __iomem *epit_base;
    int irq_num;
    bool is_opened;
} epit_timer_t;

static epit_timer_t epit_timer;

static irqreturn_t epit_irq_handler(int irq, void *dev_id)
{
    // TODO: interrupt handler
    return IRQ_HANDLED;
}

static int epit_open(struct inode *inode, struct file *filp)
{
    if (epit_timer.is_opened) {
        return -EBUSY;
    }

    epit_timer.is_opened = true;
    filp->private_data = &epit_timer;

    return 0;
}

static int epit_release(struct inode *inode, struct file *filp)
{
    epit_timer.is_opened = false;

    return 0;
}

static ssize_t epit_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
    // TODO: read timer value
    return -EINVAL;
}

static ssize_t epit_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
    // TODO: write timer value
    return -EINVAL;
}

static const struct file_operations epit_fops = {
    .owner = THIS_MODULE,
    .open = epit_open,
    .release = epit_release,
    .read = epit_read,
    .write = epit_write,
};

static int __init epit_init(void)
{
    int ret;

    // Allocate device number
    epit_timer.dev_num = 0;
    ret = alloc_chrdev_region(&epit_timer.dev_num, 0, 1, DEV_NAME);
    if (ret < 0) {
        printk(KERN_ERR "Failed to allocate device number: %d\n", ret);
        return ret;
    }

    // Initialize cdev structure
    cdev_init(&epit_timer.cdev, &epit_fops);
    epit_timer.cdev.owner = THIS_MODULE;

    // Add cdev to system
    ret = cdev_add(&epit_timer.cdev, epit_timer.dev_num, 1);
    if (ret < 0) {
        printk(KERN_ERR "Failed to add cdev: %d\n", ret);
        goto err_cdev_add;
    }

    // Create device class and device
    epit_timer.cls = class_create(THIS_MODULE, DEV_NAME);
    if (IS_ERR(epit_timer.cls)) {
        ret = PTR_ERR(epit_timer.cls);
        printk(KERN_ERR "Failed to create class: %d\n", ret);
        goto err_cls_create;
    }

    epit_timer.dev = device_create(epit_timer.cls, NULL, epit_timer.dev_num, NULL, DEV_NAME);
    if (IS_ERR(epit_timer.dev)) {
        ret = PTR_ERR(epit_timer.dev);
        printk(KERN_ERR "Failed to create device: %d\n", ret);
        goto err_dev_create;
    }

    // Map epit base address
    epit_timer.epit_base = ioremap(EPIT_BASE_ADDR, 0x1000);
    if (!epit_timer.epit_base) {
        printk(KERN_ERR "Failed to map epit base address\n");
        ret = -ENOMEM;
        goto err_ioremap;
    }

    // Request irq
    epit_timer.irq_num = EPIT_IRQ_NUM;
    ret = request_irq(epit_timer.irq_num, epit_irq_handler, IRQF_TRIGGER_RISING, DEV_NAME, &epit_timer);
    if (ret < 0) {
        printk(KERN_ERR "Failed to request irq: %d\n", ret);
        goto err_request_irq;
    }

    // Success
    printk(KERN_INFO "epit timer driver loaded\n");
    return 0;

err_request_irq:
    iounmap(epit_timer.epit_base);

err_ioremap:
    device_destroy(epit_timer.cls, epit_timer.dev_num);

err_dev_create:
    class_destroy(epit_timer.cls);

err_cls_create:
    cdev_del(&epit_timer.cdev);

err_cdev_add:
    unregister_chrdev_region(epit_timer.dev_num, 1);

    return ret;
}

static void __exit epit_exit(void)
{
    // Free irq
    free_irq(epit_timer.irq_num, &epit_timer);

    // Unmap epit base address
    iounmap(epit_timer.epit_base);

    // Destroy device class and device
    device_destroy(epit_timer.cls, epit_timer.dev_num);
    class_destroy(epit_timer.cls);

    // Remove cdev from system
    cdev_del(&epit_timer.cdev);

    // Free device number
    unregister_chrdev_region(epit_timer.dev_num, 1);

    printk(KERN_INFO "epit timer driver unloaded\n");
}

module_init(epit_init);
module_exit(epit_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("imx6ull epit timer driver");

此代码仅供参考，其中的TODO注释需要根据具体的应用场景来实现。同时，还需要在Makefile中添加编译该模块的规则。