Linux Device driver character device

Can no longer be streamlined, suitable for getting started.

1#include <linux/module.h>2#include <linux/init.h>3 4#include <asm/uaccess.h>5#include <linux/types.h>6#include <linux/fs.h>7#include <linux/cdev.h>8 structmengc_dev{9         Chardata[ -];Ten         structCdev Cdev; One }; A intMengmajor; - structMengc_dev Meng_device; -  the voidExit_mengc_dev (void) - { -dev_t Devno = MKDEV (Mengmajor,1); -Cdev_del (&Meng_device.cdev); +Unregister_chrdev_region (Devno,1); - } + intMeng_open (structInode*inode,structFile *Filep) A { at         return 0; - } - intMeng_release (structInode*inode,structFile *Filep) - { -                 return 0; - } in  -ssize_t Meng_read (structFile*filep,Char__user*buf,size_t count,loff_t*f_ops) to { +         if(*f_ops>=strlen (meng_device.data)) -                 return 0; the         if(Copy_to_user (Buf,meng_device.data,strlen (meng_device.data))) *         { $                 return-1;Panax Notoginseng         } -*f_ops+=strlen (meng_device.data); the         returnstrlen (meng_device.data); + } A  thessize_t Meng_write (structFile*filep,Const Char__user*buf,size_t count,loff_t*f_ops) + { -         if(count> the) $Count= the; $         if(Copy_from_user (meng_device.data,buf,count)) -         { -                 return-Efault; the         } -         returncount;Wuyi } the  -  Wu structFile_operations meng_fops= - { About. read=Meng_read, $. write=Meng_write, -. open=Meng_open, -. release=Meng_release - }; A intInit_mengc_dev (void) + { the         intre; -dev_t dev=0; $Re=alloc_chrdev_region (&dev,1,1,"Mengcdev"); the         if(re<0) the         { thePrintk"MENG_DEVC Register failed.\n"); the                 returnre; -         } inMengmajor=MAJOR (dev); thememset (&meng_device,0,sizeof(Meng_device)); theCdev_init (&meng_device.cdev,&meng_fops); AboutMeng_device.cdev.owner=This_module; themeng_device.cdev.ops=&Meng_fops; theRe=cdev_add (&meng_device.cdev,dev,1); the         if(RE) +         { -Printk"MENGDEVC Add faild.\n"); the         }Bayi         return 0; the } the Module_init (Init_mengc_dev); -Module_exit (Exit_mengc_dev);

Save the above file to MENGCDEV.C

Then create a makefile file in the same directory, the file content is as follows (only this line):

Obj-m: =MENGCDEV.O

Then execute make-c/lib/modules/' uname-r '/build/m= ' pwd ' in this directory the command executed successfully the day before yesterday is installed the source code package, specifically can refer to other materials, Ubuntu just apt-get install several packages, The Redhat series requires only a few yuminstall. Of course, there is a development environment, that is, GCC and the like.

Once the compilation is complete, the Mengcdev.ko module can be generated.

Insert this module with root insmod Mengcdev.ko

Then go to the/proc/device and find the appropriate device number.

Cat/proc/devices |grep Meng

If the output is as follows:

248 Mengcdev

The execution

Mknod/dev/mengcdev C 248 1, pay attention to replace 248 with the actual output value

And then you can test it. Echo Hello >/dev/mengcdev

Cat/dev/mengcdev