字符设备驱动模块 之 基本通用模块
字符设备驱动模块 之 基本通用模块
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;
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