驱动基础——字符设备1

使用命令建立一个设备
s




驱动代码

#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);




下面是建立设备

mknod -m 666 /dev/env_dev c 263 262

然后写个makefile

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


然后写个测试程序

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