Linux核心學習－misc雜項裝置驅動

Linux裡面的misc雜項裝置是主裝置號為10的驅動裝置，它的註冊跟使用比較的簡單，所以比較適用於功能簡單的裝置。

它有自己的裝置結構體：

 struct miscdevice  {
     int minor;
     const char *name;
     const struct file_operations *fops;
     struct list_head list;
     struct device *parent;
     struct device *this_device;
     const char *nodename;
     mode_t mode;
 };
它在標頭檔linux/miscdevice.h裡面有定義，

其中minor是misc裝置的副裝置號，misc裝置主要依賴minor去區分，如果設定為MISC_DYNAMIC_MINOR則表示系統自動分配未使用的minor

nodename是在/dev下面建立的裝置驅動節點，

fops是驅動主體處理函數入口指標

 

主要使用到的函數有：

int misc_register(struct miscdevice * misc);
int misc_deregister(struct miscdevice *misc);

misc01.c檔案

#include <linux/init.h>#include <linux/module.h>#include <linux/fs.h>#include <linux/miscdevice.h>/////////////////////////////////////////////////MODULE_LICENSE("Dual BSD/GPL");int open_state = 0;/////////////////////////////////////////////////int misc01_open(struct inode *inode, struct file *filp){    if (open_state == 0)    {        open_state = 1;        printk("misc01 open!\n");        return 0;    }    printk("misc01 has been open!\n");    return -1;}int misc01_release(struct inode *inode, struct file *filp){    if (open_state == 1)    {        open_state = 0;        printk("misc01 release!\n");        return 0;    }    printk("misc01 has not been open yet!\n");    return -1;}ssize_t misc01_read(struct file *filp, char *buf,        size_t count, loff_t fpos){    printk("misc01 read!\n");    return 0;}ssize_t misc01_write(struct file *filp, char *buf,        size_t count, loff_t fpos){    printk("misc01 write!\n");    return 0;}int misc01_ioctl(struct inode *inode, struct file *filp,        unsigned int cmd, unsigned long arg){    printk("ioctl is called!\n");    printk("cmd:%d arg:%d\n", cmd, arg);    return 0;}/////////////////////////////////////////////////struct file_operations fops = {    .owner      =   THIS_MODULE,    .open       =   misc01_open,    .release    =   misc01_release,    .write      =   misc01_write,    .read       =   misc01_read,    .ioctl      =   misc01_ioctl};struct miscdevice dev = {    .minor  =   MISC_DYNAMIC_MINOR,    .fops    =   &fops,    .name   =   "misc01",    .nodename = "misc01_node"};int setup_misc01(void){        return misc_register(&dev);}/////////////////////////////////////////////////static int __init misc01_init(void){    printk("misc01 init!\n");    return setup_misc01();}static void __exit misc01_exit(void){    printk("misc01 exit!\n");    misc_deregister(&dev);}/////////////////////////////////////////////////module_init(misc01_init);module_exit(misc01_exit);

Makefile檔案

#Makefileobj-m:=misc01.oPWD:=$(shell pwd)K_DIR:=/lib/modules/$(shell uname -r)/buildall:$(MAKE) -C $(K_DIR) M=$(PWD) modulesclean:$(MAKE) -C $(K_DIR) M=$(PWD) cleantest:misc01_test.ogcc -o $@ {1}lt;

misc01_test.c檔案

#include <stdio.h>#include <sys/stat.h>#include <sys/ioctl.h>#include <fcntl.h>#include <errno.h>/////////////////////////////////////////////////int main(int argc, char **argv){    int fd;    fd = open("/dev/misc01_node", O_RDONLY);    if (fd < 0)    {        printf("open /dev/misc01_node failed!\n");        printf("%s\n", strerror(errno));        return -1;    }        printf("open /dev/misc01_node ok!\n");    if (ioctl(fd, 6) != 0)    {        printf("ioctl failed!\n");        printf("%s\n", strerror(errno));    }    else        printf("ioctl ok!\n");    close(fd);    return 0;}