最简单的linux驱动和测试例子

#include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/fcntl.h> #include <linux/cdev.h> #include <linux/version.h> #include <linux/vmalloc.h> #include <linux/ctype.h> #include <linux/pagemap.h> #include <linux/slab.h> #include "Demo.h" MODULE_AUTHOR("Yangjin"); MODULE_LICENSE("Dual BSD/GPL"); struct demo_dev *demo_devices; static unsigned char demo_inc = 0;//全局变量，每次只能打开一个设备 static u8 demo_buffer[256]; int demo_open(struct inode *inode, struct file *filp) { struct demo_dev *dev; if (demo_inc > 0) return -ERESTARTSYS; demo_inc++; dev = container_of(inode->i_cdev, struct demo_dev, cdev); filp->private_data = dev; return 0; } int demo_release(struct inode *inode, struct file *filp) { demo_inc--; return 0; } ssize_t demo_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { int result; loff_t pos = *f_pos; //pos: offset if (pos >= 256) { result = 0; goto out; } if (count > (256 - pos)) count = 256 - pos; pos += count; if (copy_to_user(buf, demo_buffer+*f_pos, count)) { count = -EFAULT; goto out; } *f_pos = pos; out: return count; } ssize_t demo_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos) { ssize_t retval = -ENOMEM; loff_t pos = *f_pos; if (pos > 256) goto out; if (count > (256 - pos)) count = 256 - pos; pos += count; if (copy_from_user(demo_buffer+*f_pos, buf, count)) { retval = -EFAULT; goto out; } *f_pos = pos; retval = count; out: return retval; } int demo_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg) { if (cmd == COMMAND1) { printk("ioctl command 1 successfully\n"); return 0; } if (cmd == COMMAND2) { printk("ioctl command 2 successfully\n"); return 0; } printk("ioctl error\n"); return -EFAULT; } long demo_unlock_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { if (cmd == COMMAND1) { printk("ioctl command 1 successfully\n"); return 0; } if (cmd == COMMAND2) { printk("ioctl command 2 successfully\n"); return 0; } printk("ioctl error\n"); return -EFAULT; } long demo_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { if (cmd == COMMAND1) { printk("ioctl command 1 successfully\n"); return 0; } if (cmd == COMMAND2) { printk("ioctl command 2 successfully\n"); return 0; } printk("ioctl error\n"); return -EFAULT; } loff_t demo_llseek(struct file *filp, loff_t off, int whence) { loff_t pos; pos = filp->f_pos; switch (whence) { case 0: pos = off; break; case 1: pos += off; break; case 2: default: return -EINVAL; } if ((pos > 256) || (pos < 0)) return -EINVAL; return filp->f_pos = pos; } struct file_operations demo_fops = { .owner = THIS_MODULE, .llseek = demo_llseek, .read = demo_read, .write = demo_write, //.ioctl = demo_ioctl, .unlocked_ioctl = demo_unlock_ioctl, .compat_ioctl = demo_compat_ioctl, .open = demo_open, .release = demo_release, }; void demo_cleanup_module(void) { dev_t devno = MKDEV(DEMO_MAJOR, DEMO_MINOR); if (demo_devices) { cdev_del(&demo_devices->cdev); kfree(demo_devices); } unregister_chrdev_region(devno, 1); } //Init module流程： //1）注册设备号MKDEV； //2）注册设备驱动程序,即初始化cdev结构（嵌入到demo_devices结构中） int demo_init_module(void) { int result; dev_t dev = 0; dev = MKDEV(DEMO_MAJOR, DEMO_MINOR); result = register_chrdev_region(dev, 1, "DEMO"); if (result < 0) { printk(KERN_WARNING "DEMO: can't get major %d\n", DEMO_MAJOR); return result; } demo_devices = kmalloc(sizeof(struct demo_dev), GFP_KERNEL); if (!demo_devices) { result = -ENOMEM; goto fail; } memset(demo_devices, 0, sizeof(struct demo_dev)); cdev_init(&demo_devices->cdev, &demo_fops); demo_devices->cdev.owner = THIS_MODULE; demo_devices->cdev.ops = &demo_fops; //将创建的字符设备与file_operations中各函数操作连接起来 result = cdev_add(&demo_devices->cdev, dev, 1); if (result) { printk(KERN_NOTICE "error %d adding demo\n", result); goto fail; } return 0; fail: demo_cleanup_module(); return result; } module_init(demo_init_module); module_exit(demo_cleanup_module);