驱动基础——字符设备3
字符设备驱动中的 read接口的使用，简单实例 驱动部分代码
#include <linux/module.h> #include <linux/slab.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/cdev.h> #include <linux/major.h> #include <asm/uaccess.h> static ssize_t flash_env_dev_open(struct inode *inode,struct file *file) { return 0; } static ssize_t flash_env_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { unsigned char *p = (unsigned char *)kmalloc(11,GFP_KERNEL); memcpy(p,"lingjiujianke",13); if(!(copy_to_user(buf,p,10))) { printk("<1>copy ok\n"); } return 0; } static ssize_t flash_env_dev_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { unsigned char *p=kmalloc(11,GFP_KERNEL); if(copy_from_user(p,buf,10)==0) { printk("<1>%s\n",p); } kfree(p); return 0; } static ssize_t flash_env_dev_ioctl(struct inode *inode,struct file *file,unsigned int cmd,unsigned long arg) { printk("<1> %d\n",cmd); switch(cmd){ case 0: printk("<1> in flash 0\n"); break; case 1: printk("<1> in flash 1\n"); break; default: printk("<1> others\n"); } return 0; } static const struct file_operations flash_fops = { .owner =THIS_MODULE, .open = flash_env_dev_open, .read = flash_env_dev_read, .write = flash_env_dev_write, .ioctl = flash_env_dev_ioctl, }; #define MAX_FLASH_ENV_MINORS 262 static struct cdev flash_cdev; dev_t dev; static __init int flash_env_dev_init(void) { int res; dev=MKDEV(263,262); cdev_init(&flash_cdev,&flash_fops); res=register_chrdev_region(dev, MAX_FLASH_ENV_MINORS, "/dev/read_dev"); if(res) printk("<1> fuck\n"); res=cdev_add(&flash_cdev,dev,MAX_FLASH_ENV_MINORS); if(res) printk("<1> fuck2 \n"); /* devfs_mk_dir("flash_env_dev");*/ printk("<1> Hello World\n"); return 0; } static void __exit flash_env_dev_exit(void) { unregister_chrdev_region(dev,MAX_FLASH_ENV_MINORS); printk("<1> exit Hello World\n"); } module_init(flash_env_dev_init); module_exit(flash_env_dev_exit); |
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Makefile部分代码
KERNELDIR = /usr/src/kernels/2.6.27.25-170.2.72.fc10.i686 PWD := $(shell pwd) obj-m := chrdev.o modules: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules gcc test_chrdev.c -o test_chrdev clean: rm -rf *.o *.ko test_chrdev Module.* module* *.mod.c |
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测试代码
#include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/ioctl.h> #include <stdlib.h> #include <string.h> int main() { int fd=0; int ret=0; unsigned char buffer[20]; fd=open("/dev/read_dev", O_RDWR); if(fd<0) printf("open file error\n"); memset(buffer,0,20); ret=read(fd,buffer,10); if(ret<0) printf("ioctl error\n"); if(buffer) { printf("the buffer is |%s|\n",buffer); } return 0; } |
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