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Old 10-08-2013, 08:14 PM   #1
RaspPi
LQ Newbie
 
Registered: Oct 2013
Location: Ottawa, IL
Distribution: Wheezy (Debian)
Posts: 7
Blog Entries: 1

Rep: Reputation: Disabled
Disable or Redirect keystrokes from keyboard


This is my 1st post! yay.

I need help quickly. I need to disable/prevent/redirect the output from some keyboard devices in /dev/input/by-path/...
Reason to disable output: these are USB Proximity readers that appear as a keyboard to Linux. Since I'm reading the data into my C program directly from the device using the read() call. I do not want the characters to show up on the monitor.
The real keyboard should still work though.

I can give more detail if needed.

Any help at all would be greatly accepted.

Last edited by RaspPi; 10-08-2013 at 08:50 PM. Reason: make issue easier to understand
 
Old 10-08-2013, 09:38 PM   #2
RaspPi
LQ Newbie
 
Registered: Oct 2013
Location: Ottawa, IL
Distribution: Wheezy (Debian)
Posts: 7
Blog Entries: 1

Original Poster
Rep: Reputation: Disabled
Found solution

ok, I ended up finding the solution. It was as simple as making an IOCtl(xxx,EVIOCGRAB,1) call to get exclusive access to the device.

Source: http://stackoverflow.com/questions/7...hen-block-them
Here's the full code.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <dirent.h>
#include <linux/input.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/select.h>
#include <sys/time.h>
#include <termios.h>
#include <signal.h>

int main(int argc, char* argv[])
{
struct input_event ev[64];
int fevdev = -1;
int result = 0;
int size = sizeof(struct input_event);
int rd;
int value;
char name[256] = "Unknown";
char *device = "/dev/input/event0";


fevdev = open(device, O_RDONLY);
if (fevdev == -1) {
printf("Failed to open event device.\n");
exit(1);
}

result = ioctl(fevdev, EVIOCGNAME(sizeof(name)), name);
printf ("Reading From : %s (%s)\n", device, name);

printf("Getting exclusive access: ");
result = ioctl(fevdev, EVIOCGRAB, 1);
printf("%s\n", (result == 0) ? "SUCCESS" : "FAILURE");

while (1)
{
if ((rd = read(fevdev, ev, size * 64)) < size) {
break;
}

value = ev[0].value;

if (value != ' ' && ev[1].value == 1 && ev[1].type == 1) {
printf ("Code[%d]\n", (ev[1].code));
}
}

printf("Exiting.\n");
result = ioctl(fevdev, EVIOCGRAB, 1);
close(fevdev);
return 0;
}
 
  


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