点亮GT2440开发板上的led(基于IO内存实现)
首先的感谢这微博主:http://blog.csdn.net/jianchi88/article/details/6848035
我在这先粘下我的开发版的数据手册的led截图，毕竟涉及到硬件知识,也是为了让大家读更加容易明白:
驱动程序源码:
#include <linux/module.h> //内核模块头文件
#include <linux/moduleparam.h> //内核模块参数头文件
#include <linux/kernel.h> //printk头文件
#include<asm/io.h>//ioremap需要
//包含有可装载模块需要的大量符合和函数的定义；
#include <linux/init.h>
//指定初始化和清除函数；
//struct file_operactions 相关头文件
#include <linux/fs.h>
#include <asm/uaccess.h>
//struct cdev 相关头文件
#include <linux/types.h>
#include <linux/cdev.h>
//定义设备名称
#define DEVICE_NAME "led"
//定义主次设备号
static unsigned int LedMajor=0;
static unsigned int LedMinor=0;
/* 注册字符设备 */
static struct cdev *led_cdev;
static dev_t dev; //设备号
volatile unsigned int long *gpb_con = NULL;
volatile unsigned int long *gpb_data = NULL;
static int led_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
if((cmd>1) | (cmd<0) | (arg>3) | (arg<0))
return -EINVAL;
switch(cmd)
{
case 0:
*gpb_data|= (1<<(arg+5)); //0
break;
case 1:
*gpb_data&= ~(1<<(arg+5)); //1
break;
default:
return -EINVAL;
}
return 0;
}
/*static int led_open(struct inode *inode, struct file *file)
{
printk("led_open\n");
//映射I/O内存
gpb_con = (volatile unsigned long *)ioremap(0x56000010,16); //0x56000010为GPIOB控制寄存器的物理地址
gpb_data = gpb_con+1; //这里+1是加了4个字节，因为指针+1是以指针的长度为单位的（unsigned long *）
// 配置GPB5,6,7,8为输出
*gpb_con &= ~((1<<(5)) & (1<<(6)) & (1<<(7)) & (1<<(8)));
// 初始化为灭
*gpb_data |=(1<<5) | (1<<6) | (1<<7) | (1<<8);
printk("leaving led_open\n");
return 0;
}
*/
/*static int led_release(struct inode *inode,struct file *file)
{
printk("close major=%d, minor=%d\n", imajor(inode), iminor(inode));
return 0;
}
*/
static struct file_operations chardev_fops={
.owner = THIS_MODULE,
//.open = led_open,
//.release = led_release,
.ioctl = led_ioctl,
};
static int __init dev_init(void)
{
int result;
/*分配设备编号*/
if(LedMajor)
{
dev=MKDEV(LedMajor,LedMinor);//创建设备编号
result=register_chrdev_region(dev,1,DEVICE_NAME);
}
else
{
result=alloc_chrdev_region(&dev,LedMinor,1,DEVICE_NAME);
LedMajor=MAJOR(dev);
}
if(result<0)
{
printk(KERN_WARNING"LED: cannot get major %d \n",LedMajor);
return result;
}
/* 注册字符设备 */
led_cdev=cdev_alloc();//为struct cdev 分配空间
cdev_init(led_cdev,&chardev_fops);//初始化struct cdev
led_cdev->owner=THIS_MODULE;
result=cdev_add(led_cdev,dev,1);
if(result)
printk("<1>Error %d while register led device!\n",result);
printk("initialzed.\n");
//映射I/O内存
gpb_con = (volatile unsigned long *)ioremap(0x56000010,16); //0x56000010为GPIOB控制寄存器的物理地址
gpb_data = gpb_con+1; //这里+1是加了4个字节，因为指针+1是以指针的长度为单位的（unsigned long *）
// 配置GPB5,6,7,8为输出
*gpb_con &= ~((1<<(5)) & (1<<(6)) & (1<<(7)) & (1<<(8)));
// 初始化为灭
*gpb_data |=(1<<5) | (1<<6) | (1<<7) | (1<<8);
return 0;
}
static void __exit dev_exit(void)
{
unregister_chrdev_region(MKDEV(LedMajor,LedMinor),1);
cdev_del(led_cdev);
}
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Bai");
测试程序就补贴出来了，我想大家都不会感到有难度。
运行结果：
