Linux character devices-Automatically create device numbers and device nodes

Linux character Devices - automatically create device numbers and device nodes

First write an example of automatically assigning a character device number and device node and the APP

Manual Installation steps:

Insmod My_char_dev.ko

No more device nodes to install

Then the test app .

./my_char_dev_app 1

1#include <linux/module.h>2#include <linux/init.h>3#include <linux/io.h>4#include <linux/fs.h>5#include <asm/device.h>//The following three header files are created due to the need to add dynamic6#include <linux/device.h>7#include <linux/cdev.h>8#include"my_cdev.h"9 structCdev Cdev;Tendev_t Devno;//here is the dynamic allocation of the device number and the dynamic creation of device nodes need to use One struct class*Cdev_class; A  - intMy_cdev_open (structInode *node,structFile *Filp) - { thePrintk"My_cdev_open sucess!\n"); -     return 0; - } -  + LongMy_cdev_ioctl (structFile *filp, unsignedintCMD, unsignedLongArg) - { +     Switch(CMD) A     { at          Caseled_on: -Printk"led_on is set!\n"); -             return 0; -          CaseLed_off: -Printk"Led_off is set!\n"); -             return 0; in         default : -             return-EINVAL; to     } + } -  the structFile_operations my_cdev_fops= * { $. Open =My_cdev_open,Panax Notoginseng. Unlocked_ioctl =My_cdev_ioctl, -  the }; +  A Static intMy_cdev_init (void) the { +     intret; -     /** Dynamic allocation of device numbers*/ $ret = Alloc_chrdev_region (&devno,0,1,"My_chardev"); $     if(ret) -     { -Printk"alloc_chrdev_region fail!\n"); theUnregister_chrdev_region (Devno,1); -         returnret;Wuyi     } the     Else -     { WuPrintk"alloc_chrdev_region sucess!\n"); -     } About     /** Description of structure initialization*/ $Cdev_init (&cdev,&my_cdev_fops); -     /** Describe structure registration*/ -ret = Cdev_add (&cdev,devno,1); -     if(ret) A     { +Printk"Cdev Add fail.\n"); theUnregister_chrdev_region (Devno,1); -         returnret; $     } the     Else the     { thePrintk"Cdev Add sucess!\n"); the     } -  inCdev_class = Class_create (This_module,"My_chardev"); the     if(Is_err (cdev_class)) the     { AboutPrintk"Create class fail!\n"); theUnregister_chrdev_region (Devno,1); the         return-1; the     } +     Else -     { thePrintk"Create class sucess!\n");Bayi     } the  theDevice_create (Cdev_class,null,devno,0,"My_chardev"); -      -     return 0; the } the Static voidMy_cdev_exit (void) the { the Device_destroy (CDEV_CLASS,DEVNO); - Class_destroy (cdev_class); theCdev_del (&Cdev); theUnregister_chrdev_region (Devno,1); thePrintk"my_cdev_exit sucess!\n");94 } the Module_init (my_cdev_init); the Module_exit (my_cdev_exit); theModule_license ("GPL");98Module_author ("Yefei"); AboutModule_description ("Yefei Driver");

1 #ifndef __my_cdev_h__ 2 #define __my_cdev_h__34#define led_magic ' L '5#define led_on _ IO (led_magic,0)6#define led_off _io (led_magic,1)78#endif

1#include <sys/stat.h>2#include <sys/types.h>3#include <sys/ioctl.h>4#include <fcntl.h>5#include <stdio.h>6#include"my_cdev.h"7 8 intMainintargcChar*argv[])9 {Ten     intFD; One     intcmd; A     if(ARGC <2) -     { -printf"Please enter secend param!\n"); the         return 0; -     } -cmd = atoi (argv[1]); -FD = open ("/dev/my_chardev", O_RDWR); +     if(FD <0) -     { +printf"Open Dev/my_chardev fail!\n"); A Close (FD); at         return 0; -     } -     Switch(CMD) -     { -          Case 1: - IOCTL (fd,led_on); in              Break; -          Case 2: to IOCTL (fd,led_off); +              Break; -         default: the              Break; *     } $ Close (FD);Panax Notoginseng     return 0; -}

1 obj-m: = my_char_dev.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

Linux character devices-Automatically create device numbers and device nodes