一、驱动模块的加载

1. 静态  编译进内核
2. 动态  编译成模块 如下：

解决方法

结果

 

led电灯例子

1. 创建一个led.c 
2. 修改Makefile、Kconfig
3. make modules
4. cp drivers/char/led.ko /home/linux/nfs/rootfs
5. 开发板 insmod led.ko
6. 去 /home/linux/nfs/rootfs 上 写程序.c
7. arm-linux-gcc 程序.c
8. 开发板 创建节点 mknod /dev/led c 253 0
9. 开发板 运行程序 

~/linux-2.6.32.2/drivers/char/   led.c 内核(操作系统)代码

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/cdev.h>
#include <linux/module.h>
#include <asm/io.h>
#include <asm/string.h>

#define MAJOR_NUM 253
#define MINOR_NUM 0
#define DEV_NAME "led"
#define DEV_NUM 1
#define GPBCON 0x56000010
#define GPBDAT 0x56000014

static volatile unsigned long * gpbcon;
static volatile unsigned long * gpbdat;

static void init_led(void)						
{
	// 配置GPB5引脚功能为输出
	*gpbcon &= ~(3 << 10);
	*gpbcon |= (1 << 10);

	// 将GPB5引脚电平置高
	*gpbdat |= (1 << 5);
}

static void led_on(void)
{
	// 将GPB5引脚电平置低
	*gpbdat &= ~(1 << 5);
}

static void led_off(void)
{
	// 将GPB5引脚电平置高
	*gpbdat |= (1 << 5);
}

static int open (struct inode * inode, struct file * file)
{
	init_led();
	printk("led open ...\n");
	return 0;
}

static ssize_t read (struct file * file, char __user * buf, size_t len, loff_t * offset)
{
	printk("led read ...\n");
	return 0;
}

static ssize_t write (struct file * file, const char __user * buf, size_t len, loff_t * offset)
{
	int ret = strlen(buf);
	if(!strcmp(buf, "ledon"))
		led_on();
	else if(!strcmp(buf, "ledoff"))
		led_off();
	else
		ret = -1;

	printk("led write ...\n");
	return ret;
}

static int close (struct inode * inode, struct file * file)
{
	printk("led close ...\n");
	return 0;
}

static struct file_operations fops = 
{
	.owner = THIS_MODULE,
	.open = open,
	.read = read,
	.write = write,
	.release = close
};
static struct cdev cdev;
static dev_t dev;

static int __init led_init(void)
{
	int ret = 0;
	dev = MKDEV(MAJOR_NUM, MINOR_NUM);

	cdev_init(&cdev, &fops);

	ret = cdev_add(&cdev, dev, DEV_NUM);
	if(ret < 0)
		goto err_cdev_add;

	ret = register_chrdev_region(dev, DEV_NUM, DEV_NAME);
	if(ret < 0)
		goto err_register_chrdev_region;

	gpbcon = ioremap(GPBCON, sizeof(*gpbcon));
	gpbdat = ioremap(GPBDAT, sizeof(*gpbdat));

	printk("led_init  ...\n");

	return ret;

err_cdev_add:
	cdev_del(&cdev);
	printk("led cdev_add failed\n");
	return ret;

err_register_chrdev_region:
	unregister_chrdev_region(dev, DEV_NUM);
	cdev_del(&cdev);
	printk("led register_chrdev_region\n");	
	return ret;
}

static void __exit led_exit(void)
{
	iounmap(gpbcon);
	iounmap(gpbdat);
	unregister_chrdev_region(dev, DEV_NUM);
	cdev_del(&cdev);
	printk("led_exit  ###############################\n");
}

module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");

~/nfs/rootfs  led_app.c 应用层(栈)代码

 1 #include <fcntl.h>                                                                                                                                                                 
  2 #include <stdio.h>
  3 #include <stdlib.h>
  4 #include <string.h>
  5 #include <unistd.h>
  6 
  7 int main(int argc, const char *argv[])
  8 {
  9     int fd = open("/dev/led",O_RDWR);
 10     if (fd < 0)
 11     {
 12         perror("open led fail");
 13         return -1;
 14     }
 15 
 16     unsigned char buf[48] = {0};
 17 
 18     while(1)
 19     {
 20         write(fd,"ledon",strlen("ledon"));
 21         sleep(2);
 22         write(fd,"ledoff",strlen("ledoff"));
 23         sleep(2);
 24     }
 25     close(fd);
 26     return 0;
 27 }

拷贝数据函数 

不要直接从内核操作应用层代码，也不要直接从应用层操作内核代码

可以间接操作，通过函数copy_from_user()、copy_to_user()

 

 设备分类