Inappropriate ioctl (EVIOCGRAB) for 'keyboard' device - c

Question

I am trying to debug evmuxd tool (physical keyboard multiplexer with switching support) from following github source.I installed bluez library and successfully compiled source code. However when I try to run as man page suggest I am getting following error:
sudo evmuxd /dev/input/event7
Could not grab keyboard for exclusive use: Inappropriate ioctl for device
From code below you can see that ioctl (fd, EVIOCGRAB, 1) returns error
#include <linux/input.h>
#include <linux/uinput.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#define UINPUT "/dev/uinput"
static int
open_uinput (const char *name)
{
int fd;
struct uinput_user_dev dev = { 0, };
int i;
fd = open (UINPUT, O_WRONLY | O_NDELAY);
if (fd == -1) {
perror (UINPUT);
return -1;
}
if (ioctl(fd, UI_SET_EVBIT, EV_KEY) == -1) {
perror ("Could not enable key events");
goto fail;
}
for (i = 0; i < KEY_CNT; i++) {
if (ioctl(fd, UI_SET_KEYBIT, i) == -1) {
perror ("Could not enable a key event");
goto fail;
}
}
if (ioctl(fd, UI_SET_EVBIT, EV_REP) == -1) {
perror ("Could not enable autorepeat events");
goto fail;
}
strncpy (dev.name, name, UINPUT_MAX_NAME_SIZE);
dev.id.bustype = BUS_VIRTUAL;
dev.id.vendor = 0x0666;
dev.id.product = 0x8086;
dev.id.version = 1;
if (write (fd, &dev, sizeof (dev)) != sizeof (dev)) {
perror (UINPUT);
goto fail;
}
if (ioctl(fd, UI_DEV_CREATE) == -1) {
perror ("Could not create the virtual keyboard");
goto fail;
}
return fd;
fail:
close (fd);
return -1;
}
static int
open_input (char *dev)
{
int version;
int features;
int fd;
int norepeat[2] = { 0, 0 };
fd = open (dev, O_RDWR);
if (fd == -1) {
perror (dev);
return -1;
}
if (ioctl (fd, EVIOCGVERSION, &version) == -1) {
perror ("Could not read input protocol version");
goto fail;
}
if (version >> 16 != EV_VERSION >> 16) {
fprintf (stderr, "Bad input subsystem version");
goto fail;
}
if (ioctl (fd, EVIOCGBIT(0, EV_MAX), &features) == -1) {
perror ("Could query device for supported features");
goto fail;
}
if (!(features & EV_KEY)) {
fprintf (stderr, "Device not capable of producing key press event.");
goto fail;
}
if (ioctl (fd, EVIOCGRAB, 1) == -1) {
perror ("Could not grab keyboard for exclusive use");
goto fail;
}
if (ioctl (fd, EVIOCSREP, norepeat) == -1) {
perror ("Could not disable autorepeat");
goto fail;
}
return fd;
fail:
close (fd);
return -1;
}
int
main (int argc, char *argv[])
{
int uinput[2], input;
struct input_event event;
int active = 0;
int switching = 0;
if (argc != 2) {
fprintf (stderr, "Usage: %s /dev/input/event<n>\n", argv[0]);
return 1;
}
input = open_input (argv[1]);
if (input == -1)
return 1;
uinput[0] = open_uinput ("evmuxd primary");
if (uinput[0] == -1)
return 1;
uinput[1] = open_uinput ("evmuxd secondary");
if (uinput[1] == -1)
return 1;
while (1) {
switch (read (input, &event, sizeof(event))) {
case -1:
perror ("Error reading from event device");
return 1;
case sizeof(event):
break;
default:
fprintf (stderr, "Short read from the event device.\n");
return 1;
}
switch (write (uinput[active], &event, sizeof(event))) {
case -1:
perror ("Error forwarding the event");
return 1;
case sizeof(event):
break;
default:
fprintf (stderr, "Short write forwarding the event.\n");
return 1;
}
if (event.type == EV_KEY
&& event.code == KEY_SCROLLLOCK
&& event.value == 0) {
switching = 1;
}
if (event.type == EV_SYN && switching) {
switching = 0;
active = !active;
}
}
return 0;
}
So what is the problem and how I can fix it?