#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 <[email protected]>"); 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;