oO( A Brief Introduction to Linux's Input Event System )
If your Linux kernel is version 2.6.0 or higher,
go look in /dev/input. You might see something like this:
total 0
crw-r--r-- 1 root root 13, 64 Dec 31 1969 event0
crw-r--r-- 1 root root 13, 65 Dec 31 1969 event1
crw-r--r-- 1 root root 13, 66 Dec 31 1969 event2
crw-r--r-- 1 root root 13, 67 Dec 31 1969 event3
crw------- 1 beppu root 13, 0 Dec 31 1969 js0
crw-r--r-- 1 root root 13, 63 Dec 31 1969 mice
crw-r--r-- 1 root root 13, 32 Dec 31 1969 mouse0
The Linux kernel has implemented a nice system whereby
you can open any of these files and wait for events to happen.
When an event happens, the kernel will write a predictably
sized data structure to these virtual files.
This works for practically every input device that Linux
supports, whether it be a keyboard, a mouse, a joystick
or something more exotic. Just `cat /proc/bus/inputs/devices`
to see what you have at your disposal.
Furthermore, this system lets you receive makes and
breaks which are really useful for anyone trying to write
an application that needs to handle complex input sequences
(like a game).
oO( Why do I like it so much? )
It's like a Grand Unified Input System that fits perfectly
into the everything-is-a-file model that Unix users have
come to know and love. It'll take any input device,
regardless of what bus it's connected to and make it so
that you, the programmer, can treat them equally in
your code. It's also super simple to program for.
And now, with this Perl module, it's become even easier.
oO( What does this perl module distribution provide? )
Linux::Input
This is the main class that lets you access the
input system.
`perldoc Linux::Input` for the details.
Linux::Input::Joystick
This is a subclass of Linux::Input that reads
joystick events. They are very similar to the
universal catch-all events, but not quite the same.
This particular interface existed from around the
2.2 series, and the new input system is a direct
descendant of this work.
When you use this module, you'll want to read
from joystick device files. They're typically
named like:
/dev/input/js0
/dev/input/js9
/dev/js0
/dev/js1
NOTE: You don't have to use Linux::Input::Joystick
to access joysticks. You can use Linux::Input for
joysticks, too. However, you will not be reading
from joystick device files. Instead, you will read
from one of the event device files.
evtest.pl
After you install this distribution, try typing:
sudo evtest.pl /dev/input/event*
Then, move you mouse, push some keys, move
your gamepad around, etc.... This will help
figure out if this distribution works on your
system.
Special thanks to Vojtech for creating this system in the first place.
I hope other Unixes implement it, too.
