linux设备驱动归纳总结（三）：3.设备驱动面向对象思想和lseek的实现

#include <linux/module.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/cdev.h> #include <asm/uaccess.h> #include <linux/errno.h> #define DEBUG_SWITCH 1 #if DEBUG_SWITCH #define P_DEBUG(fmt, args...) printk("<1>" "<kernel>[%s]"fmt, __FUNCTION__, ##args) #else #define P_DEBUG(fmt, args...) printk("<7>" "<kernel>[%s]"fmt, __FUNCTION__, ##args) #endif #define DEV_SIZE 100 struct _test_t{ char kbuf[DEV_SIZE]; unsigned int major; unsigned int minor; unsigned int cur_size; dev_t devno; struct cdev test_cdev; }; int test_open(struct inode *node, struct file *filp) { struct _test_t *dev; dev = container_of(node->i_cdev, struct _test_t, test_cdev); filp->private_data = dev; return 0; } int test_close(struct inode *node, struct file *filp) { return 0; } ssize_t test_read(struct file *filp, char __user *buf, size_t count, loff_t *offset) { int ret; struct _test_t *dev = filp->private_data; if(*offset >= DEV_SIZE){//如果偏移量已经超过了数组的容量 return count ? - ENXIO : 0; //count为0则返回0，表示读取0个数据成功 } //count不为0则分会错误号，地址越界 if(*offset + count > DEV_SIZE){ //如果读取字节数超过了最大偏移量 count = DEV_SIZE - *offset; //则减少读取字节数。 } /*copy_to_user的参数也要改一下*/ if (copy_to_user(buf, dev->kbuf + *offset, count)){ ret = - EFAULT; }else{ ret = count; dev->cur_size -= count; //读取后数组的字节数减少 *offset += count; //偏移量增加 P_DEBUG("read %d bytes, cur_size:[%d]\n", count, dev->cur_size); } return ret; //返回实际写入的字节数或错误号 } ssize_t test_write(struct file *filp, const char __user *buf, size_t count, loff_t *offset) { int ret; struct _test_t *dev = filp->private_data; if(*offset >= DEV_SIZE){//如果偏移量已经超过了数组的容量 return count ? - ENXIO : 0; //count为0则返回0，表示读取0个数据成功 } //count不为0则分会错误号，地址越界 if(*offset + count > DEV_SIZE){ //如果读取字节数超过了最大偏移量 count = DEV_SIZE - *offset; //则减少读取字节数。 } /*copy_from_user的参数也要改一下*/ if(copy_from_user(dev->kbuf + *offset, buf, count)){ ret = - EFAULT; }else{ ret = count; dev->cur_size += count; //写入后数组的字节数增加 *offset += count; //偏移量增加 P_DEBUG("write %d bytes, cur_size:[%d]\n", count, dev->cur_size); P_DEBUG("kbuf is [%s]\n", dev->kbuf); } return ret; //返回实际写入的字节数或错误号 } loff_t test_llseek (struct file *filp, loff_t offset, int whence) { loff_t new_pos; //新偏移量 loff_t old_pos = filp->f_pos; //旧偏移量 switch(whence){ case SEEK_SET: new_pos = offset; break; case SEEK_CUR: new_pos = old_pos + offset; break; case SEEK_END: new_pos = DEV_SIZE + offset; break; default: P_DEBUG("unknow whence\n"); return - EINVAL; } if(new_pos < 0 || new_pos > DEV_SIZE){ //如果偏移量越界，返回错误号 P_DEBUG("f_pos failed\n"); return - EINVAL; } filp->f_pos = new_pos; return new_pos; //正确返回新的偏移量 } struct file_operations test_fops = { .open = test_open, .release = test_close, .write = test_write, .read = test_read, .llseek = test_llseek, }; struct _test_t my_dev; static int __init test_init(void) //模块初始化函数 { int result = 0; my_dev.cur_size = 0; my_dev.major = 0; my_dev.minor = 0; /*1.申请设备号*/ if(my_dev.major){ my_dev.devno = MKDEV(my_dev.major, my_dev.minor); result = register_chrdev_region(my_dev.devno, 1, "test new driver"); }else{ result = alloc_chrdev_region(&my_dev.devno, my_dev.minor, 1, "test alloc diver"); my_dev.major = MAJOR(my_dev.devno); my_dev.minor = MINOR(my_dev.devno); } if(result < 0){ P_DEBUG("register devno errno!\n"); goto err0; } printk("major[%d] minor[%d]\n", my_dev.major, my_dev.minor); /*2.注册设备*/ cdev_init(&my_dev.test_cdev, &test_fops); my_dev.test_cdev.owner = THIS_MODULE; result = cdev_add(&my_dev.test_cdev, my_dev.devno, 1); if(result < 0){ P_DEBUG("cdev_add errno!\n"); goto err1; } printk("hello kernel\n"); return 0; err1: unregister_chrdev_region(my_dev.devno, 1); err0: return result; } static void __exit test_exit(void) //模块卸载函数 { /*1.从内核中删除cdev*/ cdev_del(&my_dev.test_cdev); /*2.注销设备号*/ unregister_chrdev_region(my_dev.devno, 1); printk("good bye kernel\n"); } module_init(test_init); module_exit(test_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("xoao bai"); MODULE_VERSION("v0.1");