#include?<linux/module.h>?

?

#include?<linux/init.h>?

?

#include?<linux/fs.h>?

?

#include?<asm/uaccess.h>?

?

MODULE_LICENSE("GPL");//?設置這個模塊的協議為?GPL??

?

#define?MAJOR_NUM?2918?//主設備號?

?

//聲明Read函數?

static?ssize_t?device_read(struct?file?*,?char?*,?size_t,?loff_t*);?

//聲明Write函數?

static?ssize_t?device_write(struct?file?*,?const?char?*,?size_t,?loff_t*);?

?

//初始化字符設備驅動的file_operations結構體?

?

struct?file_operations?device_fops?=?

?

{?

.read=device_read,?

.write=device_write,?

};?

?

static?int?device_var?=?0;?//"globalvar"設備的全局變量?

?

static?int?__init?device_init(void)?

{?

int?ret;?

//注冊設備驅動?

ret?=?register_chrdev(MAJOR_NUM,?"device",?&device_fops);?

if?(ret)?

{?

printk("device?register?failure");?

}?

else?

{?

printk("device?register?success");?

}?

return?ret;?

}?

?

static?void?__exit?device_exit(void)?

{?

int?ret?=?0;?

//注銷設備驅動?

unregister_chrdev(MAJOR_NUM,?"device");?

if?(ret)?

{?

printk("device?unregister?failure");?

}?

else?

{?

printk("device?unregister?success");?

}?

}?

//READ?

static?ssize_t?device_read(struct?file?*filp,?char?*buf,?size_t?len,?loff_t?*off)?

{?

//將device_var從內核空間復制到用戶空間?

if?(copy_to_user(buf,?&device_var,?sizeof(int)))?

{?

return?-?EFAULT;?

}?

return?sizeof(int);?

}?

static?ssize_t?device_write(struct?file?*filp,?const?char?*buf,?size_t?len,?loff_t?*off)?

{?

//將用戶空間的數據復制到內核空間的device_var?

if?(copy_from_user(&device_var,?buf,?sizeof(int)))?

{?

return?-?EFAULT;?

}?

return?sizeof(int);?

}?

module_init(device_init);?

module_exit(device_exit);?

編譯為模塊：

命令為：make -C /lib/modules/3.0.0-7-generic/build M(等號)/home/shi/c_dev/modules

Makefile為

?

#?From《Linux?Device?Drivers》3rd?Edition?

#?Makefile?

ifneq?($(KERNELRELEASE),)?

#?call?from?kernel?build?system?

?

obj-m???:=?device.o?

?

else?

?

KERNELDIR??=?/lib/modules/$(shell?uname?-r)/build?

PWD???????:=?$(shell?pwd)?

?

default:?

????$(MAKE)?-C?$(KERNELDIR)?M=$(PWD)?modules?

?

endif??

完成之后，講模塊加入到內核中去

sudo insmod ./device.ko

查看所有模塊

lsmod

刪除模塊

sudo rmmod ./device.ko

測試程序

?

#include?<sys/types.h>?

#include?<sys/stat.h>?

#include?<stdio.h>?

#include?<fcntl.h>?

main()?

{?

int?fd,num;?

//打開"/dev/device"?

fd?=?open("/dev/device",?O_RDWR,?S_IRUSR?|?S_IWUSR);?

if?(fd?!=?0)?

{?

//初次讀device?

read(fd,?&num,?sizeof(int));?

printf("The?device?is?%d\n",?num);?

//寫device?

printf("Please?input?the?num?written?to?device\n");?

scanf("%d",?&num);?

write(fd,?&num,?sizeof(int));?

//再次讀device?

read(fd,?&num,?sizeof(int));?

printf("The?device?is?%d\n",?num);?

//關閉"/dev/device"?

close(fd);?

}?

else?

{?

printf("Device?open?failure\n");?

}?

}??

運行結果

shi@smkoo:~/c_dev$ ./test
The device is 134514219
Please input the num written to device
1
The device is 1
?

轉載于:https://blog.51cto.com/1793109/709506

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