驱动基础——字符设备1

#include <linux/module.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> 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) {     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,     .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/env_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);

mknod -m 666 /dev/env_dev c 263 262

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

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