Linux驱动入门——编写第一个驱动

int open(const char *pathname, int flags, mode_t mode);

#include <linux/module.h>
 
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
#include <linux/gfp.h>
 
/* 1. 确定主设备号                                                                 */
static int major = 0;
static char kernel_buf[1024];
static struct class *hello_class;
 
 
#define MIN(a, b) (a < b ? a : b)
 
/* 3. 实现对应的open/read/write等函数，填入file_operations结构体                   */
static ssize_t hello_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset)
{
  int err;
  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  err = copy_to_user(buf, kernel_buf, MIN(1024, size));
  return MIN(1024, size);
}
 
static ssize_t hello_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset)
{
  int err;
  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  err = copy_from_user(kernel_buf, buf, MIN(1024, size));
  return MIN(1024, size);
}
 
static int hello_drv_open (struct inode *node, struct file *file)
{
  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  return 0;
}
 
static int hello_drv_close (struct inode *node, struct file *file)
{
  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  return 0;
}
 
/* 2. 定义自己的file_operations结构体                                              */
static struct file_operations hello_drv = {
  .owner   = THIS_MODULE,
  .open    = hello_drv_open,
  .read    = hello_drv_read,
  .write   = hello_drv_write,
  .release = hello_drv_close,
};
 
/* 4. 把file_operations结构体告诉内核：注册驱动程序                                */
/* 5. 谁来注册驱动程序啊？得有一个入口函数：安装驱动程序时，就会去调用这个入口函数 */
static int __init hello_init(void)
{
  int err;
  
  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  major = register_chrdev(0, "hello", &hello_drv);  /* /dev/hello */
 
 
  hello_class = class_create(THIS_MODULE, "hello_class");
  err = PTR_ERR(hello_class);
  if (IS_ERR(hello_class)) {
    printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
    unregister_chrdev(major, "hello");
    return -1;
  }
  
  device_create(hello_class, NULL, MKDEV(major, 0), NULL, "hello"); /* /dev/hello */
  
  return 0;
}
 
/* 6. 有入口函数就应该有出口函数：卸载驱动程序时，就会去调用这个出口函数           */
static void __exit hello_exit(void)
{
  printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
  device_destroy(hello_class, MKDEV(major, 0));
  class_destroy(hello_class);
  unregister_chrdev(major, "hello");
}
 
 
/* 7. 其他完善：提供设备信息，自动创建设备节点                                     */
 
module_init(hello_init);
module_exit(hello_exit);
 
MODULE_LICENSE("GPL");
 
 

 
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
 
/*
 * ./hello_drv_test -w abc
 * ./hello_drv_test -r
 */
int main(int argc, char **argv)
{
  int fd;
  char buf[1024];
  int len;
  
  /* 1. 判断参数 */
  if (argc < 2) 
  {
    printf("Usage: %s -w <string>\n", argv[0]);
    printf("       %s -r\n", argv[0]);
    return -1;
  }
 
  /* 2. 打开文件 */
  fd = open("/dev/hello", O_RDWR);
  if (fd == -1)
  {
    printf("can not open file /dev/hello\n");
    return -1;
  }
 
  /* 3. 写文件或读文件 */
  if ((0 == strcmp(argv[1], "-w")) && (argc == 3))
  {
    len = strlen(argv[2]) + 1;
    len = len < 1024 ? len : 1024;
    write(fd, argv[2], len);
  }
  else
  {
    len = read(fd, buf, 1024);    
    buf[1023] = '\0';
    printf("APP read : %s\n", buf);
  }
  
  close(fd);
  
  return 0;
}