Linux hybrid character devices and linux hybrid characters

Linux hybrid character devices and linux hybrid characters

Linux hybrid character Devices

Hybrid Device Driver Model

 

Hybrid device Concept

In Linux, there is a type of character devices that have the same master device number (10) but different sub-device numbers. We call such devices as miscdevice ). All the devices form a linked list. During device access, the kernel finds the corresponding devices according to the device number.

 

1. device description

In Linux, struct miscdevice is used to describe a Hybrid device.
Struct miscdevice {
Int minor;/* Device Number */
Const char * name;/* device name */
Const struct file_operations * fops;/* File Operations */
Struct list_head list;
Struct device * parent;
Struct device * this_device;
};

 

2. device registration

Use the misc_register function in Linux to register a Hybrid device driver.
Int misc_register (struct miscdevice * misc)

 

 

 

First, write an example of intercommunication between kernel-state data and user-state data and an APP

Manual installation steps:

Insmod my_char_dev.ko

 

No more device node installation required

 

Then test the app.

./My_char_dev_app 1

 

 

 1 #include <linux/module.h> 2 #include <linux/init.h> 3 #include <linux/io.h> 4 #include <linux/miscdevice.h> 5 #include <linux/fs.h> 6 #include <asm/uaccess.h> 7  8 unsigned int param=0; 9 10 static int my_open(struct inode *node,struct file *filep )11 {12     printk("Open my_open sucess!\n");13     return 0;14 }15 static int my_read(struct file *filp,char __user *buf,size_t size,loff_t *pos)16 {17     printk("Read my_read sucess!\n");18     param = 500;19     copy_to_user(buf, &param, 4);20     return 0;21 }22 23 24 struct file_operations my_miscdev_fops =25 {     26     .open = my_open,27     .read = my_read,28 };29 30 struct miscdevice my_miscdev = 31 {32     .minor = 200,33     .name =  "my_miscdev",34     .fops = &my_miscdev_fops,35 };36 static int my_miscdev_init(void)37 {38     int ret;39     ret = misc_register(&my_miscdev);40     if(ret != 0)41         printk("miscdev register fail.\n!");42     return 0;43 44 }45 static void my_miscdev_exit(void)46 {47     misc_deregister(&my_miscdev);48 49 }50 51 MODULE_LICENSE("GPL");52 53 module_init(my_miscdev_init);54 module_exit(my_miscdev_exit);

 

 

 1 #include <stdio.h> 2 #include <sys/stat.h> 3 #include <sys/types.h> 4 #include <sys/ioctl.h> 5 #include <fcntl.h> 6  7 int main(char argc,char *argv[]) 8 { 9     int fd;10     int cmd;11     int param = 0;12     if(argc < 2)13     {14         printf("please enter the second param!\n");15         return 0;    16     }17     cmd = atoi(argv[1]);18     fd = open("/dev/my_miscdev",O_RDWR);19     if(fd < 0)20     {21         printf("Open /dev/my_miscdev fail.\n");22     }23 24     switch(cmd)25     {26         case 1:27             printf("Second param is %c\n",*argv[1]);28             read(fd, &param, 4);29             printf("Read Param is %d.\n",param);30             break;31         default :32             break;33     }34     close(fd);35     return 0;36 37 }

 

 

1 obj-m := my_miscdev.o2 KDIR := /home/win/dn377org/trunk/bcm7252/linux/3 all:4     make -C $(KDIR) M=$(PWD) modules CROSS_COMPILE=arm-linux- ARCH=arm5 clean:6     rm -f *.ko *.o *.mod.o *.mod.c *.symvers *.bak *.order