IOCTL in Linux device drivers

Memdev.h

#ifndef _memdev_h#define _memdev_h#define mem_magic ' m ' #define Mem_restart _io (mem_magic, 0)//Use the kernel-provided macros to generate commands #define MEM _set     _iow (mem_magic, 1, int)//change command to pass a shaping parameter to the kernel #endif

Driver MEMDEV.C

#include <linux/module.h> #include <linux/init.h> #include <linux/cdev.h> #include <linux/fs.h > #include <asm/uaccess.h> #include "memdev.h" struct Cdev mdev;dev_t devno;static long mem_ioctl (struct file* FILP, unsigned int cmd, unsigned long arg) {switch (cmd) {case MEM_RESTART:PRINTK ("Memdev restart.\n"); Break;case Mem_set: PRINTK ("Arg is%ld\n", arg);//Print the parameters passed down by the user to see if they are consistent break;default:return-einval;break;} return 0;} struct File_operations memfops = {. Llseek = Mem_lseek,.unlocked_ioctl = mem_ioctl,// The function parameters also change};static __init int memdev_init (void) {Cdev_init (&mdev, 2.6.36) after the kernel is ioctl,2.6.36 after the unlocked_ioctl. &memfops); alloc_chrdev_region (&devno, 0, 2, "Memdev"), Cdev_add (&mdev, Devno, 2);p RINTK ("Memdev_init Success\n "); return 0;} static void __exit memdev_exit (void) {Cdev_del (&mdev); Unregister_chrdev_region (Devno, 2);p RINTK ("Memdev_exit Success\n ");} Module_init (Memdev_init); Module_exit (Memdev_exit); Module_license ("GPL"); Module_author ("Liuwei"); Module_dEscription ("char driver"); 

Application MEM_READ.C

#include <stdio.h> #include <sys/ioctl.h> #include <sys/types.h> #include <sys/stat.h># Include <fcntl.h> #include "memdev.h" int main (int argc, char *argv[]) {int FD = open ("/dev/memdev", O_RDWR); if (FD ==< c0/>-1) {perror ("open"); return-1;} IOCTL (FD, Mem_restart);//Send two control commands, one without parameters, one with an integer parameter of the IOCTL (FD, Mem_set, x); close (FD); return 0;}

The device number is dynamically assigned in the driver and the device number assigned by the system to Memdev is viewed through cat/proc/devices.

Use the command Mknod/dev/memdev C 252 0 To create a device node. Where 252 system assigned the device number.

Drive a simple makefile

Ifeq ($ (kernelrelease),) PWD: = $ (Shell PWD) kerneldir? =/home/farsight/samba/linux-2.6.36installdir? =/nfs/rootnfs/ modules:$ (make)-C $ (Kerneldir) m=$ (PWD) modulesinstall:cp *.ko/nfs/rootnfs/clean:rm-rf *.o *.ko *.mod.c. *.cmd modules. Order module.symvers. Tmp_versionselseobj-m: = MEMDEV.O endif

IOCTL in Linux device drivers