LED驱动，自动创建设备节点

下面是我写的LED简单驱动代码，Arm平台(lpc3250)如下实现功能：
1>把代码编译后，添加到内核模块使LED灭10秒，然后亮10秒
2>在/dev目录自动挂载LED设备节点，可以“Echo "1" >/dev/led”控制LED
3>再实现在开机自动运行，自动添加到内核中。当然是修改启动代码实现的。
4>最后我编译进内核中，下面我先把代码贴出来。

/**
 * @：0xf4028004和0xf4028008是GPIO端口3输出与输出寄存器虚拟地址
 * 地址是我直接算出来的，可以用io_p2v()函数实现
 * @: __raw_writel()向地址写数据
 * @: class_create()创建总线，class_destroy()删除
 * @: device_create()创建设备节点,device_destroy()删除
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/errno.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/interrupt.h>

#include <asm/uaccess.h>
#include <mach/irq.h>
#include <asm/io.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <mach/hardware.h>
#include <mach/platform.h>
#include <mach/lpc32xx_gpio.h>

#define DEVNAME "LED"
#define LED_MAJOR 251

#define P3_SET ((volatile unsigned int) 0xf4028004)
#define P3_CLR ((volatile unsigned int) 0xf4028008)

struct led_dev
{
    struct cdev cdev;
    unsigned int value;
};

struct led_dev *led_dev;

int led_open(struct inode *inode, struct file *filp)
{
    struct led_dev *dev;
    dev = container_of(inode->i_cdev, struct led_dev, cdev);
    filp->private_data = dev;
    try_module_get(THIS_MODULE);
    return 0;
}

int led_release(struct inode *inode, struct file *filp)
{
    module_put(THIS_MODULE);
    return 0;
}

static int led_write(struct file *filp, const char __user *buf, size_t count, loff_t *ppos)
{
    struct led_dev *dev = filp->private_data;
    if(copy_from_user(&(dev->value), buf , 1))
    {
        return -EFAULT;
    }
    if(dev->value == 1)
        __raw_writel(1 << 5, P3_SET);
    else
        __raw_writel(1 << 5, P3_CLR);
    return 1;
}

int led_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg)
{
    struct led_dev *dev = filp->private_data;
    switch (cmd)
    {
        case 0:
            dev->value = 0;
            __raw_writel(1 << 5, P3_CLR);
            break;
        case 1:
            dev->value = 1;
            __raw_writel(1 << 5, P3_SET);
            break;
        default :
            dev->value = 1;
            __raw_writel(1 << 5, P3_SET);
            break;
    }
    return 0;
}

struct file_operations led_fops =
{
    .owner = THIS_MODULE,
    .write = led_write,
    .ioctl = led_ioctl,
    .open = led_open,
    .release = led_release,
};

static void led_setup_cdev(struct led_dev *dev, int index)
{
    int err, devno = MKDEV(LED_MAJOR, 0);
    cdev_init(&dev->cdev, &led_fops);
    dev->cdev.owner = THIS_MODULE;
    dev->cdev.ops = &led_fops;
    err = cdev_add(&dev->cdev, devno, 1);
    if(err)
        printk(KERN_NOTICE "Error adding LED");
}

struct class *led_class;
static int __init led_init(void)
{
    int i,result;    
    dev_t dev = MKDEV(LED_MAJOR, 0);
    result = register_chrdev_region(dev, 1, DEVNAME);
    if(result < 0)
        return result;
    led_dev = kmalloc(sizeof(struct led_dev), GFP_KERNEL);
    if(!led_dev)
    {
        result = ~ENOMEM;
        goto fail;
    }
    memset(led_dev, 0, sizeof(struct led_dev));
    led_setup_cdev(led_dev, 0);
    led_class = class_create(THIS_MODULE, "led_class");
    device_create(led_class, NULL, MKDEV(LED_MAJOR, 0), "LED","LED%d", 0);
    __raw_writel(1 << 5, P3_SET);
    for(i = 0; i< 5; i++)
    {
        msleep(1000);
    }
    __raw_writel(1 << 5, P3_CLR);
    for(i = 0; i < 10; i++)
    {    
        msleep(1000);        
    }
    __raw_writel(1 << 5, P3_SET);
    return 0;
fail:
    unregister_chrdev_region(dev, 1);
    return result;
}

static void __exit led_exit(void)
{
    cdev_del(&led_dev->cdev);
    device_destroy(led_class, MKDEV(LED_MAJOR, 0));
    class_destroy(led_class);
    kfree(led_dev);
    unregister_chrdev_region(MKDEV(LED_MAJOR, 0), 1);
}

module_init(led_init);
module_exit(led_exit);

MODULE_LICENSE("GPL");

内核模块在开机自动添加到内核中：
在/etc/rc.d/rc.local文件中，添加插入内核模块的命令就行了
insmod led.ko

内核模块编译进内核中，下面以LED驱动为例子：
第一：将您写的led.c 文档添加到/driver/mtd/maps/ 目录下。
第二：修改/driver/mtd/maps目录下的kconfig文档：
config MTD_LED
tristate “LED driver"
第三：修改该目录下makefile文档。
添加如下内容：obj-$(CONFIG_MTD_LED)    += led.o

然后make menuconfig，在device drivers该选项下面找到LED驱动模块，选中M直接编译成内核模块。