Home ›

The Linux keyboard driver

Issue 14

From Issue #14
June 1995

Jun 01, 1995  By Andries E. Brouwer
 in
Our Kernel Korner series continues with an article describing the linux Keyboard driver. This artilce is not for “Kernel Hackers” only—in fact, it will be most useful to those who wish to use their own keyboard to its fullest potential, and those who want to write programs to take advantage of the many features in the Linux keyboard driver.
Using loadkeys

Use loadkeys to change the code produced by the BackSpace key from Delete to BackSpace:


% loadkeys
keycode 14 = BackSpace

Assign the string “emacs\n” to the function key F12, and “rm *~\n” to Shift-F12 (the keycode 88 was found using showkey; the F66 is a random unused function key symbol):


% loadkeys
 keycode 88 = F12
 shift keycode 88 = F66
 string F12 = "emacs\n"
 string F66 = "rm *~\n"

Create the compose combination that will compose | and S into $:


% loadkeys
 compose '|' 'S' to '$'
 compose 'S' '|' to '$'

Reset to some default state:


% loadkeys -d
Sequel

After the above handling, the obtained character(s) are put in the raw tty queue. Depending on the mode of the tty, they will be processed and transferred to the cooked tty queue. (Don't confuse raw mode as stty knows it, with the raw scancode mode discussed above.) Finally, the application will get them when it does getchar();.

Andries Brouwer, aeb@cwi.nl, has used Unix for various mathematical, linguistic, and playful purposes the past 20 years or so. He might be known to some for the first net release of hack.

______________________

Comments

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

how to test power and ptt keys??

lakshmi's picture
Submitted by lakshmi (not verified) on Tue, 08/31/2010 - 07:07.

Hai i want to test power and ptt keys. I am using evtest to test my keys on the keypad. But my driver wont generate any interrupt for power and ptt keys so how to test these keys??

general awareness

Anonymous's picture
Submitted by Anonymous (not verified) on Sat, 08/28/2010 - 04:15.

general awareness

Getting keyboard scancodes

email's picture
Submitted by email (not verified) on Sat, 02/21/2009 - 09:53.

The article is confused.
Please write a simple non-blocking function.

This can be the prototype:

bool keypressed( int& scancode );

bye
miro

linux keypad driver

Anonymous's picture
Submitted by Anonymous (not verified) on Sat, 02/14/2009 - 11:10.

the scancode related information are good

Re : Kernel Korner: The Linux keyboard driver

Anonymous's picture
Submitted by Anonymous on Fri, 03/05/2004 - 03:00.

Good One !! But really missing the source code as example.

Re: Kernel Korner: The Linux keyboard driver

Anonymous's picture
Submitted by Anonymous on Wed, 12/03/2003 - 03:00.

It's better to explain with a practical keyboard source code.

Re: Kernel Korner: The Linux keyboard driver

Anonymous's picture
Submitted by Anonymous on Sun, 04/25/2004 - 02:00.

can u pls send the c code for keyboard device driver

need c code of keyboard driver

G Abbas's picture
Submitted by G Abbas (not verified) on Thu, 12/22/2005 - 03:32.

i will be greatful if someone help me. i need c code fo generic keyboard driver.

Can you please send me

Anonymous's picture
Submitted by Anonymous (not verified) on Wed, 05/17/2006 - 10:05.

Can you please send me source code of a generic keyboard driver?

Need it for Windows/Dos environment

Anonymous's picture
Submitted by Anonymous (not verified) on Fri, 11/19/2004 - 14:45.

Hi

I need to access certain keys on a Pentuim PC keyboard using ISO. But ISO just specifies the H and no C files and it only gives you the CRT device not the keyboard-subdevice of the CRT.

So I've decided to do a search for keyboard-drivers. And now I want the complete c code for a keyboard driver, please?

Re: Kernel Korner: The Linux keyboard driver

Anonymous's picture
Submitted by Anonymous on Sat, 09/27/2003 - 02:00.

not a practical example... too confuse

Yes you are right

Kenson Goo's picture
Submitted by Kenson Goo (not verified) on Mon, 12/25/2006 - 01:13.

Linux needs to simplify everything so that our grandparents can use the system easily. I bet my grandparents would prefer Microsoft keyboard like http://www.compkeyboard.com/archives/microsoft-natural-ergonomic-keyboar...

than a Linux system with 4 pages of tutorial on keyboard

Dude, your an idiot. Your

Anonymous's picture
Submitted by Anonymous (not verified) on Fri, 01/05/2007 - 20:04.

Dude, your an idiot. Your grandparents are very unlikely to be writing keyboard drivers for Linux or Windows.

Grandparents

Anonymous's picture
Submitted by Anonymous (not verified) on Sat, 12/05/2009 - 11:33.

Oh, yeah? Well, my grandparents are awesome like that: 'Cept they write drivers for *nix only!

key state

Anonymous's picture
Submitted by Anonymous on Fri, 10/18/2002 - 02:00.

getchar() is a blocking call and when you press a button the corresponding character is output to the terminal. Would if all I wanted was the state of any given key at any given time? Doing this on PS2 Linux is quite easy with the js0 device for composing a bit-feild containing the state of each controller button this frame. Is their a non-blocking, non-printing way to obtain the key state of any given key?

Source code for keyboard.c in on your computer

Tim Crawford's picture
Submitted by Tim Crawford (not verified) on Fri, 01/12/2007 - 01:33.

If you install the kernel source code you can find the source
code in /usr/src/linux/drivers/char/keyboard.c

Webcast
More Resources
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers

Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.

Learn More

Sponsored by AMD

White Paper
More Resources
Red Hat White Paper: Using an Open Source Framework to Catch the Bad Guy

Built-in forensics, incident response, and security with Red Hat Enterprise Linux 6

Every security policy provides guidance and requirements for ensuring adequate protection of information and data, as well as high-level technical and administrative security requirements for a system in a given environment. Traditionally, providing security for a system focuses on the confidentiality of the information on it. However, protecting the data integrity and system and data availability is just as important. For example, when processing United States intelligence information, there are three attributes that require protection: confidentiality, integrity, and availability.

Learn more about catching the bad guy in this free white paper.

Learn More

Sponsored by DLT Solutions