字符设备驱动(三)
2017-04-29 08:41
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dev_fifo.c
Makefile
instatll.sh
test.c
#include <linux/init.h> #include <linux/module.h> #include <linux/cdev.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/slab.h> #include <linux/sched.h> #include <linux/export.h> #include <asm/setup.h> #include <asm/uaccess.h> #include <asm/current.h> MODULE_LICENSE("Dual BSD/GPL"); extern char *saved_command_line; //指定的主设备号 #define MAJOR_NUM 232 //自己的字符设备 struct mycdev { int len; unsigned char buffer[256]; //全局内存 struct cdev cdev; //记录描述字符设备的结构体 }; //设备号 dev_t记录设备类型,字符,块,网络 static dev_t dev_num = {0}; //全局gcd struct mycdev *gcd; //设备类 struct class *cls; void dev_fifo_info(void) { printk(KERN_INFO "The process is \"%s\" (pid %i) (state %ld)\n", current->comm,current->pid,current->state); //printk(KERN_INFO "Kernel command line: %s\n", saved_command_line); } //打开设备 static int dev_fifo_open(struct inode *inode, struct file *file) { printk("dev_fifo_open success!\n"); dev_fifo_info(); return 0; } //读设备 static ssize_t dev_fifo_read(struct file *file, char __user *ubuf, size_t size, loff_t *ppos) { int n; int ret; char *kbuf; printk("read *ppos : %lld\n",*ppos); if(*ppos == gcd->len) //都为0返回0 return 0; //请求大大小 > buffer剩余的字节数 :读取实际记得字节数 if(size > gcd->len - *ppos) n = gcd->len - *ppos; //写进去的长度 else n = size; printk("n = %d\n",n); //从上一次文件位置指针的位置开始读取数据 kbuf = gcd->buffer + *ppos; //拷贝数据到用户空间 ret = copy_to_user(ubuf,kbuf, n); if(ret != 0) return -EFAULT; //更新文件位置指针的值 *ppos += n; printk("dev_fifo_read success!\n"); dev_fifo_info(); return n; } //写设备 static ssize_t dev_fifo_write(struct file *file, const char __user *ubuf, size_t size, loff_t *ppos) { int n; int ret; char *kbuf; printk("write *ppos : %lld\n",*ppos); //已经到达buffer尾部了 if(*ppos == sizeof(gcd->buffer)) return -1; //请求大大小 > buffer剩余的字节数(有多少空间就写多少数据) if(size > sizeof(gcd->buffer) - *ppos) n = sizeof(gcd->buffer) - *ppos; else n = size; //从上一次文件位置指针的位置开始写入数据 kbuf = gcd->buffer + *ppos; //拷贝数据到内核空间 ret = copy_from_user(kbuf, ubuf, n); if(ret != 0) return -EFAULT; //更新文件位置指针的值 *ppos += n; //更新dev_fifo.len gcd->len += n; printk("dev_fifo_write success!\n"); dev_fifo_info(); return n; } //设备操作函数接口 static const struct file_operations fifo_operations = { .owner = THIS_MODULE, .open = dev_fifo_open, .read = dev_fifo_read, .write = dev_fifo_write, }; //模块入口 int __init dev_fifo_init(void) { int ret; struct device *device; gcd = kzalloc(sizeof(struct mycdev), GFP_KERNEL); if(!gcd){ return -ENOMEM; } //设备号 : 主设备号(12bit) | 次设备号(20bit) dev_num = MKDEV(MAJOR_NUM, 0); //静态注册设备号 ret = register_chrdev_region(dev_num,1,"dev_fifo"); if(ret < 0){ //静态注册失败,进行动态注册设备号 ret = alloc_chrdev_region(&dev_num,0,1,"dev_fifo"); if(ret < 0){ printk("Fail to register_chrdev_region\n"); goto err_register_chrdev_region; } } //创建设备类 cls = class_create(THIS_MODULE, "dev_fifo"); if(IS_ERR(cls)){ ret = PTR_ERR(cls); goto err_class_create; } //初始化字符设备 cdev_init(&gcd->cdev,&fifo_operations); //添加设备到操作系统 ret = cdev_add(&gcd->cdev,dev_num,1); if (ret < 0) { goto err_cdev_add; } //导出设备信息到用户空间(/sys/class/类名/设备名) device = device_create(cls,NULL,dev_num,NULL,"dev_fifo%d",0); if(IS_ERR(device)){ ret = PTR_ERR(device); printk("Fail to device_create\n"); goto err_device_create; } printk("Register dev_fifo to system,ok!\n"); dev_fifo_info(); return 0; err_device_create: cdev_del(&gcd->cdev); err_cdev_add: class_destroy(cls); err_class_create: unregister_chrdev_region(dev_num, 1); err_register_chrdev_region: return ret; } void __exit dev_fifo_exit(void) { //删除sysfs文件系统中的设备 device_destroy(cls,dev_num ); //删除系统中的设备类 class_destroy(cls); //从系统中删除添加的字符设备 cdev_del(&gcd->cdev); //释放申请的设备号 unregister_chrdev_region(dev_num, 1); dev_fifo_info(); return; } module_init(dev_fifo_init); module_exit(dev_fifo_exit);
Makefile
ifeq ($(KERNELRELEASE),) KERNEL_DIR ?=/lib/modules/$(shell uname -r)/build PWD :=$(shell pwd) modules: $(MAKE) -C $(KERNEL_DIR) M=$(PWD) modules .PHONY:modules clean clean: $(MAKE) -C $(KERNEL_DIR) M=$(PWD) clean else obj-m := -DEXPORT_SYMTAB obj-m := dev_fifo.o endif
instatll.sh
sudo rmmod dev_fifo sudo insmod dev_fifo.ko sudo chmod 666 /dev/dev_fifo0 sudo dmesg -c
test.c
#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <string.h> #include <sys/stat.h> #include <fcntl.h> int main(int argc, const char *argv[]) { int fd ; int n; char buf[256]; fd = open("/dev/dev_fifo0",O_RDWR); if(fd < 0){ perror("Fail to open"); return -1; } else { printf("open successful ,fd = %d\n",fd); read(fd, buf, 256); printf("读取内部值:%s\n",buf); printf("输入一个值: "); scanf("%s",buf); n = write(fd,buf,strlen(buf)); read(fd, buf, strlen(buf)); printf("读取当前值:%s\n",buf); printf("write %d bytes!\n",n); if(n < 0){ perror("Fail to write"); return -1; } } return 0; }
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