LED驱动，自动创建设备节点 - 嵌入…

 

http://lttian1068.blog.163.com/blog/static/132150608200911863225866/?fromdm&isFromSearchEngine=yes
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：

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。