Call open()
for each device, and then use select()
(or (e)poll()
) to monitor all of the file descriptors together so you can detect which devices have data available to then be read()
from at any given moment.
Update: For example:
struct event_device
{
char *device;
int fd;
};
int main(int argc, char* argv[])
{
struct input_event ev[64];
int numevents;
int result = 0;
int size = sizeof(struct input_event);
int rd;
char name[256];
char* device[12];
event_device evdevs[12], *evdev;
int numevdevs = 0;
fd_set fds;
int maxfd;
device[0] = "/dev/input/event3";
device[1] = "/dev/input/event4";
// and so on...
for (int i = 0; i < 12; ++i) {
evdev = &evdevs[numevdevs];
evdev->device = device[i];
evdev->fd = open(evdev->device, O_RDONLY);
if (evdev->fd == -1) {
printf("Failed to open event device: %s.\n", evdev->device);
continue;
}
++numevdevs;
memset(name, 0, sizeof(name));
result = ioctl(evdev->fd, EVIOCGNAME(sizeof(name)), name);
printf ("Reading From : %s (%s)\n", evdev->device, name);
printf("Getting exclusive access: ");
result = ioctl(evdev->fd, EVIOCGRAB, 1);
printf("%s\n", (result == 0) ? "SUCCESS" : "FAILURE");
}
if (numevdevs == 0) {
exit(1);
}
while (1)
{
FD_ZERO(&fds);
maxfd = -1;
for (int i = 0; i < numevdevs; ++i) {
evdev = &evdevs[i];
FD_SET(evdev->fd, &fds);
if (maxfd < evdev->fd) maxfd = evdev->fd;
}
result = select(maxfd+1, &fds, NULL, NULL, NULL);
if (result == -1) {
break;
}
for (int i = 0; i < numevdevs; ++i) {
evdev = &evdevs[i];
if (!FD_ISSET(evdev->fd, &fds)) {
continue;
}
if ((rd = read(evdev->fd, ev, size * 64)) < size) {
continue;
}
numevents = rd / size;
for (int j = 0; j < numevents; ++j) {
printf ("%s: Type[%d] Code[%d] Value[%d]\n", evdev->device, ev[j].type, ev[j].code, ev[j].value);
}
}
}
printf("Exiting.\n");
for (int i = 0; i < numevdevs; ++i) {
evdev = &evdevs[i];
result = ioctl(evdev->fd, EVIOCGRAB, 0);
close(evdev->);
}
return 0;
}