CODEWITHSUNDEEP
linuxkeyboardmouseusbhid
pts
pts

Reputation: 87291

How do I read events from a HID device under Ubuntu Jaunty?

I have a Linux USB HID device (a Hama MCE), and I can read its events manually by reading cat /dev/input/event7 and cat /dev/input/event8. Whenever I press a key on the device, a few bytes become available for reading with one of the cat commands above. I have a default installation of Ubuntu Jaunty 64-bit desktop on the machine.

I think I can write a parser to interpret the bytes emitted by the device, or I'll use libhid if it's more convenient.

My questions are:

  1. How do I prevent the text-mode virtual consoles from receiving some of the key presses on the device as normal keypresses? As of now, some device keys result an Enter, a BackSpace, a PageUp or numeric keypad numbers.
  2. Similarly, how do I prevent the X server from receiving keyboard and mouse events from this device? I have several USB keyboards and mice connected to the computer. I want the X server receive events from all of them, except for this device.
  3. How do I set up that whenever the device gets connected to the computer, the command /usr/local/bin/keydumper /dev/input/event7 /dev/input/event8 (or one command for each /dev/ path) would get run, with the proper /dev/ paths substituted in the command line?

Upvotes: 5

Views: 11904

Answers (3)

user3718260
user3718260

Reputation: 191

I do not have enough points to comment sadly.

If you are looking for the definition of EVIOCGRAB try

    #include <linux/input.h>

Upvotes: 2

pts
pts

Reputation: 87291

Answering my own question based on answers from the Linux USB HID driver developers:

Question 1. and 2.: Do

ioctl(open("/dev/input/event7", O_RDONLY), EVIOCGRAB, 1);

As long as this filehandle is open, the events generated would go only to this filehandle (not to other open()s of the same device or to the system keyboard or mouse event pool). At most one process can hold a successful EVIOCGRAB at a HID device at a time. Lirc can be configured to do an EVIOCGRAB.

Question 3.: Configure udev to start the program once the device is connected.

Upvotes: 8

CrazyChris
CrazyChris

Reputation: 106

I think solution for all questions can be writing own filter device driver, or custom driver for your device. I know such a thing (filter device driver) is available on windows so something similar can be on Linux. In that filter device driver you could block all unwanted events from the target device that you wish to block, I don't really get 3 question so I don't know how to answer for that.

Upvotes: -1

Related Questions