字符设备驱动模块 之 基本通用模块

#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/device.h> /* device_create()*/

#define ADC_SIZE 0x1000 /*全局内存最大4K字节*/
#define MEM_CLEAR 0x1 /*清0全局内存*/
#define ADC_MAJOR 250 /*预设的adc的主设备号*/

static int adc_major = ADC_MAJOR;
/*adc设备结构体*/
struct adc_dev {


 struct cdev cdev; /*cdev结构体*/
 unsigned char mem[ADC_SIZE]; /*全局内存*/
};

struct adc_dev *adc_devp; /*设备结构体指针*/
/*文件打开函数*/
int adc_open(struct inode *inode, struct file *filp)
{
 /*将设备结构体指针赋值给文件私有数据指针*/
 filp->private_data = adc_devp;
 return 0;
}
/*文件释放函数*/
int adc_release(struct inode *inode, struct file *filp)
{
 return 0;
}

/* ioctl设备控制函数 */
static int adc_ioctl(struct inode *inodep, struct file *filp, unsigned
 int cmd, unsigned long arg)
{
 struct adc_dev *dev = filp->private_data;/*获得设备结构体指针*/

 switch (cmd) {
 case MEM_CLEAR:
  memset(dev->mem, 0, ADC_SIZE);
  printk(KERN_INFO "adc is set to zero\n");
  break;

 default:
  return  - EINVAL;
 }

 return 0;
}

/*读函数*/
static ssize_t adc_read(struct file *filp, char __user *buf, size_t size,
 loff_t *ppos)
{
 unsigned long p =  *ppos;
 unsigned int count = size;
 int ret = 0;
 struct adc_dev *dev = filp->private_data; /*获得设备结构体指针*/

 /*分析和获取有效的写长度*/
 if (p >= ADC_SIZE)
  return 0;
 if (count > ADC_SIZE - p)
  count = ADC_SIZE - p;

 /*内核空间->用户空间*/
 if (copy_to_user(buf, (void *)(dev->mem + p), count)) {
  ret =  - EFAULT;
 } else {
  *ppos += count;
  ret = count;

  printk(KERN_INFO "read %u bytes(s) from %lu\n", count, p);
 }

 return ret;
}

/*写函数*/
static ssize_t adc_write(struct file *filp, const char __user *buf,
 size_t size, loff_t *ppos)
{
 unsigned long p =  *ppos;
 unsigned int count = size;
 int ret = 0;
 struct adc_dev *dev = filp->private_data; /*获得设备结构体指针*/

 /*分析和获取有效的写长度*/
 if (p >= ADC_SIZE)
  return 0;
 if (count > ADC_SIZE - p)
  count = ADC_SIZE - p;

 /*用户空间->内核空间*/
 if (copy_from_user(dev->mem + p, buf, count))
  ret =  - EFAULT;
 else {
  *ppos += count;
  ret = count;

  printk(KERN_INFO "written %u bytes(s) from %lu\n", count, p);
 }

 return ret;
}

/* seek文件定位函数 */
static loff_t adc_llseek(struct file *filp, loff_t offset, int orig)
{
 loff_t ret = 0;
 switch (orig) {
 case 0:   /*相对文件开始位置偏移*/
  if (offset < 0) {
   ret =  - EINVAL;
   break;
  }
  if ((unsigned int)offset > ADC_SIZE) {
   ret =  - EINVAL;
   break;
  }
  filp->f_pos = (unsigned int)offset;
  ret = filp->f_pos;
  break;
 case 1:   /*相对文件当前位置偏移*/
  if ((filp->f_pos + offset) > ADC_SIZE) {
   ret =  - EINVAL;
   break;
  }
  if ((filp->f_pos + offset) < 0) {
   ret =  - EINVAL;
   break;
  }
  filp->f_pos += offset;
  ret = filp->f_pos;
  break;
 default:
  ret =  - EINVAL;
  break;
 }
 return ret;
}

/*文件操作结构体*/
static const struct file_operations adc_fops = {
 .owner = THIS_MODULE,
 .llseek = adc_llseek,
 .read = adc_read,
 .write = adc_write,
 .ioctl = adc_ioctl,
 .open = adc_open,
 .release = adc_release,
};

/*初始化并注册cdev*/
static void adc_setup_cdev(struct adc_dev *dev, int index)
{
 int err, devno = MKDEV(adc_major, index);

 cdev_init(&dev->cdev, &adc_fops);
 dev->cdev.owner = THIS_MODULE;
 err = cdev_add(&dev->cdev, devno, 1);
 if (err)
  printk(KERN_NOTICE "Error %d adding LED%d", err, index);
}

struct class *myclass;


/*设备驱动模块加载函数*/
int adc_init(void)
{
 int result;
 dev_t devno = MKDEV(adc_major, 0);

 /* 申请设备号*/
 if (adc_major)
  result = register_chrdev_region(devno, 1, "adc");
 else { /* 动态申请设备号 */
  result = alloc_chrdev_region(&devno, 0, 1, "adc");
  adc_major = MAJOR(devno);
 }
 if (result < 0)
  return result;

 /* 动态申请设备结构体的内存*/
 adc_devp = kmalloc(sizeof(struct adc_dev), GFP_KERNEL);
 if (!adc_devp) {    /*申请失败*/
  result =  - ENOMEM;
  goto fail_malloc;
 }

 memset(adc_devp, 0, sizeof(struct adc_dev));

 adc_setup_cdev(adc_devp, 0);

   /*自动创建设备文件*/
 myclass = class_create(THIS_MODULE,"test_char"); /*在sys下创建类目录/sys/class/test_char*/
 device_create(myclass, NULL, MKDEV(adc_major,0), NULL, "adc");  
 
 return 0;

fail_malloc:
 unregister_chrdev_region(devno, 1);
 return result;
}

/*模块卸载函数*/
void adc_exit(void)
{
 cdev_del(&adc_devp->cdev);   /*注销cdev*/
 kfree(adc_devp);     /*释放设备结构体内存*/
 unregister_chrdev_region(MKDEV(adc_major, 0), 1); /*释放设备号*/
 class_destroy(myclass);
 device_destroy(myclass,MKDEV(adc_major,0));
}

MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
MODULE_LICENSE("Dual BSD/GPL");

module_param(adc_major, int, S_IRUGO);

module_init(adc_init);
module_exit(adc_exit);

 

 

用户程序：

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
int main()
{
 int fd;
 char buf[4096];

 strcpy(buf,"Mem is char dev!");
 printf("Buf: %s\n",buf);

 fd=open("/dev/adc",O_RDWR);
 if(fd<0)
 {
   printf("open failed!\n");
  return -1;
 }
 else
  printf("open /dev/adc is success!\n");
 if(write(fd,buf,sizeof(buf))<0)
 {
  printf("write failed!\n");
  return -1;
 }
 else
  printf("write: %s\n",buf);
 lseek(fd,0,SEEK_SET);
 
 strcpy(buf,"Buf is NULL!\n");
 printf("Buf: %s\n",buf);
 
 read(fd,buf,sizeof(buf));
 
 printf("Buf: %s\n",buf);

 return 0;

 
}