Linux character device driver

This article records the driver framework for character devices:

1. Define the Cdev interface body and class structure body

#define hello_cnt 2staticint0; // The main device number is 0, you need to have the system automatically generate the main device number Static struct Cdev Hello_cdev; Static struct class *cls;

2. Construction of File_operations structural body

struct file_operations hello_fops = {     = this_module,     . Open   = Hello_open,} ; Static int hello_open (structstruct file *file) {     printk ("  hello_open\n");      return 0 ;}

3. Registration

dev_t Devid;if(Major) {/*The main device number is determined*/Devid= MKDEV (Major,0); Register_chrdev_region (Devid, hello_cnt,"Hello");} Else {     /*The main device number is 0, so the system automatically assigns us the main device number*/Alloc_chrdev_region (&devid,0, hello_cnt,"Hello"); Major=MAJOR (devid);} Cdev_init (&hello_cdev, &hello_fops); Cdev_add (&hello_cdev, Devid, hello_cnt);

4. Create a Device node

 cls = Class_create (this_module,  hello   );d Evice_create (CLS, NULL, MKDEV ( Major,  0 ), NULL,  hello0  ); //  device_create (CLS, NULL, MKDEV (Major, 1 ), NULL,  hello1  ); // /dev/hello1