#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;
}