Linux Kernel learning-MISC miscellaneous Device Driver

The MISC miscellaneous device in Linux is a driver with the master device Number 10. It is easy to register and use, so it is suitable for devices with simple functions.

It has its own device structure:

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;
};
It is defined in the header file Linux/miscdevice. h,

Minor is the sub-device number of the misc device. The MISC device depends mainly on minor. If it is set to misc_dynamic_minor, the system automatically allocates unused minor.

Nodename is a device driver node created under/dev,

Fops is the entry pointer to the main processing function.

 

The main functions used are:

Int misc_register (struct miscdevice * MISC );
Int misc_deregister (struct miscdevice * MISC );

Misc01.c File

# 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_misc0 1 (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

 
# 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 File

 
# 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 ;}