一.系统功能框架：
U-boot : 启动内核
linux kernel: 启动应用
应用： open，read，write 都是通过C库实现，汇编就相当于swi val,引发中断，通过系统调用接口在异常中断调用不同处理函数(VFS)。
二.字符设备驱动框架：
1.编写驱动：open , read, write 等功能函数的实现:
static int led_drv_open(struct inode *inode, struct file *file){
printk("led_drv_open\n");
return 0;
}
static int led_drv_write(struct file *file, const char __user *buf, size_t count, loff_t* ppos){
printk("led_drv_write\n");
return 0;
}
2.注册驱动：
①构造file_operations结构：
static struct file_operation led_drv_fops = {
.owner = THIS_MODULE,
.open = led_drv_open,
.write = led_drv_write,
}
②注册驱动：
入口函数：
int major;
int led_drv_init(void){
major = register_chrdev(0, "led_drv", &led_drv_fops); //注册字符设备,major-主设备号 mior-次设备号，app根据设备类型和主设备号调用具体驱动。
//创建设备节点：
//... class_create(THIS_MODULE, "led_drv");
//... clase_device_create(...);
return 0;
}
修饰入口函数： module_init(led_drv_init);
出口函数：void led_drv_exit(void){
unregister_chrdev(major, "led_drv");
}
修饰出口函数： module_exit(led_drv_exit);
③编译：
Makefile :
KERN_DIR=/work/system/linux-2.6.22.6 //本地编译过的linux源码目录
all:
make -C $(KERN_DIR) M=`pwd` modules
clean:
make -C $(KERN_DIR) M=`pwd` modules clean
rm -rf modules.order
obj-m += led_drv.o
④加载：
insmod led_drv.ko
cat /proc/devices
三．參考代碼：
驱动程序：first_drv.c
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h> static struct class *firstdrv_class;
static struct class_device *firstdrv_class_dev; volatile unsigned long *gpfcon = NULL;
volatile unsigned long *gpfdat = NULL; static int first_drv_open(struct inode *inode, struct file *file)
{
//printk("first_drv_open\n");
/* 配置GPF4,5,6为输出 */
*gpfcon &= ~((0x3<<(*)) | (0x3<<(*)) | (0x3<<(*)));
*gpfcon |= ((0x1<<(*)) | (0x1<<(*)) | (0x1<<(*)));
return ;
} static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
int val; //printk("first_drv_write\n"); copy_from_user(&val, buf, count); // copy_to_user(); if (val == )
{
// 点灯
*gpfdat &= ~((<<) | (<<) | (<<));
}
else
{
// 灭灯
*gpfdat |= (<<) | (<<) | (<<);
} return ;
} static struct file_operations first_drv_fops = {
.owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */
.open = first_drv_open,
.write = first_drv_write,
}; int major;
static int first_drv_init(void)
{
major = register_chrdev(, "first_drv", &first_drv_fops); // 注册, 告诉内核 firstdrv_class = class_create(THIS_MODULE, "firstdrv"); firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, ), NULL, "xyz"); /* /dev/xyz */ gpfcon = (volatile unsigned long *)ioremap(0x56000050, );
gpfdat = gpfcon + ; return ;
} static void first_drv_exit(void)
{
unregister_chrdev(major, "first_drv"); // 卸载 class_device_unregister(firstdrv_class_dev);
class_destroy(firstdrv_class);
iounmap(gpfcon);
} module_init(first_drv_init);
module_exit(first_drv_exit); MODULE_LICENSE("GPL");
测试程序：firstdrvtest.c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h> /* firstdrvtest on
* firstdrvtest off
*/
int main(int argc, char **argv)
{
int fd;
int val = ;
fd = open("/dev/xyz", O_RDWR);
if (fd < )
{
printf("can't open!\n");
}
if (argc != )
{
printf("Usage :\n");
printf("%s <on|off>\n", argv[]);
return ;
} if (strcmp(argv[], "on") == )
{
val = ;
}
else
{
val = ;
} write(fd, &val, );
return ;
}
Makefile:
KERN_DIR = /work/system/linux-2.6.22.6 all:
make -C $(KERN_DIR) M=`pwd` modules clean:
make -C $(KERN_DIR) M=`pwd` modules clean
rm -rf modules.order obj-m += first_drv.o