Linux 与设备通信的程序

Question

I can program but I don't really know much about computers. I'm using Ubuntu Linux, and I understand (on the surface) what device files are. What I'd like to do is to write a program that takes raw input from a device, eg mouse, keyboard, webcam, or microphone. I have no idea where to start. There is a book called Linux Device Drivers, but I don't know whether all of the information contained in that thick book is relevant. I'm not looking to write device drivers, although if that's required for what I want to do then I will do it. But rather, I'm looking to simply write a C++ or (preferably) a Python program that takes raw input from devices and do other things with the raw input. Could someone please tell me where to start? Which tutorials or books shall I read?

Do I just open the devices files and read from them? I could try, but here comes another problem. I don't know which device is which in the /dev/ directory, I have a Logitec air mouse, which is connected via bluetooth to a receiver. which in turn is connected to my computer via USB? But which device file should I open if I want to receive raw input from my mouse? Would it be a USB device file or a mouse device file, There are many device files in my /dev/ directory that might correspond to my mouse? which one is it, I have /dev/input/mouse0, /dev/input/mouse1, etc, and /dev/input/mice, and /dev/input/event0, /dev/input/event1. etc.? So many of them? Which one is the right one? How do I find out?

I'm sorry but I'm just very frustrated and confused as to where to start. Any help would be much appreciated.

Answer 1

With thanks to ninjalj for his/her answer, there hasn't been any detailed answers that really solves my problem. That's understandable of course, because the question wasn't very well phrased and it's an unusual thing to ask anyway in my impression.

So after some research, I'm going to answer my own problem in the hope that should anyone else be interested, or have the same problems as I did, they can get the answer here.

Where to start? I found a book called Advanced Linux Programming . It's an amazing book in my opinion, and it's downloadable under the Open Publication License. Chapter 6, "Devices", is particularly relevant to this problem. Though, all chapters are recommended because they're all very informative, and a great read if you're a wannabe geek like me.

Which device is which? You'll find this information on the aforementioned book. But in short, there are things call "major numbers" and "minor numbers" associated with each device. You can check them my running ls -l on the device files. They're where the file sizes of normal files should be. These numbers tell you what kind of device the device file is associated with, and what driver it uses. To check what these numbers mean exactly, you can refer to Linux Device List . Right now I don't yet know of a good way to check what they are offline on the Linux box itself, but there may be a way. Beware that some files in /dev/ are not actual devices files, but symbolic links, like /dev/dvd. There are all sorts of special files that do special things, just read the book!

Answer 2

Probably the mouse/keyboard/cam you are using, already has a Linux driver for it. So once, hardware is detected linux will auto load drivers for that hardware for you. To look which device file is related to which hardware device. Take a closer look at /sys directory and dmesg command entries, you'll quickly know, which device node was created recently after you inserted the hardware. Along with this you can also, check "cat /proc/devices" file to know, which Major/Minor no. correspond to your device file, or you can look for any updates in this file, when you insert the hardware.

Answer 3

/dev/input/event* talk the evdev protocol. /dev/input/mouse* probably talk some variant of the PS/2 protocol.