Simulating absolute mouse movements in Linux using uinput
10,555
I just found out that the input core propagates the EV_ABS values as absolute values to the device node, as found out from reading /dev/input/eventX (Seems so obvious now !).All along, the application controlling the cursor (X11?) was expecting relative mouse moves while I was giving it absolute values, which probably confused it!
Author by
itisravi
EE/CS dude, GlusterFS developer, Amateur road biker etc.
Updated on June 05, 2022Comments
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itisravi almost 2 years
I'm trying to move the cursor around using absolute co-ordinates. Here's the code:
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <linux/input.h> #include <linux/uinput.h> #include <signal.h> #define die(str, args...) do { \ perror(str); \ exit(EXIT_FAILURE); \ } while(0) int fd; static void signal_handler(int signo) { printf("\nCaught SIGINT\n"); if(ioctl(fd, UI_DEV_DESTROY) < 0) die("error: cannot destroy uinput device\n"); else printf("Destroyed uinput_user_dev\n\n"); close(fd); exit(EXIT_SUCCESS); } int main(void) { struct uinput_user_dev uidev; struct input_event ev; int x, y; int i; if(signal(SIGINT,signal_handler)==SIG_ERR) { printf("error registering signal handler\n"); exit(EXIT_FAILURE); } fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK); if(fd < 0) die("error: open"); if(ioctl(fd, UI_SET_EVBIT, EV_KEY) < 0) die("error: ioctl"); // if(ioctl(fd, UI_SET_KEYBIT, BTN_MOUSE) < 0) // die("error: ioctl"); if(ioctl(fd, UI_SET_KEYBIT, BTN_LEFT) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_KEYBIT, BTN_RIGHT) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_EVBIT, EV_REL) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_RELBIT, REL_X) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_RELBIT, REL_Y) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_EVBIT, EV_ABS) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_ABSBIT,ABS_X) < 0) die("error: ioctl"); if(ioctl(fd, UI_SET_ABSBIT, ABS_Y) < 0) die("error: ioctl"); memset(&uidev, 0, sizeof(uidev)); snprintf(uidev.name, UINPUT_MAX_NAME_SIZE, "uinput-sample"); uidev.id.bustype = BUS_USB; uidev.id.vendor = 0x1; uidev.id.product = 0x1; uidev.id.version = 1; uidev.absmin[ABS_X]=0; uidev.absmax[ABS_X]=1023; uidev.absfuzz[ABS_X]=0; uidev.absflat[ABS_X ]=0; uidev.absmin[ABS_Y]=0; uidev.absmax[ABS_Y]=767; uidev.absfuzz[ABS_Y]=0; uidev.absflat[ABS_Y ]=0; if(write(fd, &uidev, sizeof(uidev)) < 0) die("error: write0"); if(ioctl(fd, UI_DEV_CREATE) < 0) die("error: ioctl"); sleep(2); while(1) { printf("\nEnter the absoulte x(0-1023) and y(0-767) co-ordinates:"); scanf("%d %d",&x,&y);······· memset(&ev, 0, sizeof(struct input_event)); gettimeofday(&ev.time,NULL); ev.type = EV_ABS; ev.code = ABS_X; ev.value = x; if(write(fd, &ev, sizeof(struct input_event)) < 0) die("error: write1"); memset(&ev, 0, sizeof(struct input_event)); ev.type = EV_SYN; if(write(fd, &ev, sizeof(struct input_event)) < 0) die("error: write4"); memset(&ev, 0, sizeof(struct input_event)); ev.type = EV_ABS; ev.code = ABS_Y; ev.value = y; if(write(fd, &ev, sizeof(struct input_event)) < 0) die("error: write2"); memset(&ev, 0, sizeof(struct input_event)); ev.type = EV_SYN; if(write(fd, &ev, sizeof(struct input_event)) < 0) die("error: write3"); usleep(15000); printf("\nWritten x:%d y:%d to uinput.Press CTRL-C to quit:",x,y); } if(ioctl(fd, UI_DEV_DESTROY) < 0) die("error: cannot destroy uinput device\n"); close(fd); return 0; }The program seems to send the absolute co-ordinates that I type to the kernel's input core via uinput.
I verified this on dmesg after enabling evbug. But my mouse pointer won't move on the screen. I'm wondering what I'm messing up.
Perhaps EV_ABS is not tied to the cursor? I wonder because moving the cursor using EV_REL works fine as mentioned in this tutorial.
Sample run:
ravi@linux-lxaf:~/workspace/driver> sudo ./a.out Enter the absoulte x(0-1023) and y(0-767) co-ordinates:100 200 Written x:100 y:200 to uinput.Press CTRL-C to quit: Enter the absoulte x(0-1023) and y(0-767) co-ordinates:10 765 Written x:10 y:765 to uinput.Press CTRL-C to quit: Enter the absoulte x(0-1023) and y(0-767) co-ordinates:^C Caught SIGINT Destroyed uinput_user_devDmesg output:
ravi@linux-lxaf:~/workspace/driver> dmesg |grep input16 [ 4750.660420] input: uinput-sample as /devices/virtual/input/input16 [ 4750.660594] evbug.c: Connected device: input16 (uinput-sample at unknown) [ 4761.389036] evbug.c: Event. Dev: input16, Type: 3, Code: 0, Value: 100 [ 4761.389047] evbug.c: Event. Dev: input16, Type: 0, Code: 0, Value: 0 [ 4761.389053] evbug.c: Event. Dev: input16, Type: 3, Code: 1, Value: 200 [ 4761.389058] evbug.c: Event. Dev: input16, Type: 0, Code: 0, Value: 0 [ 4776.893126] evbug.c: Event. Dev: input16, Type: 3, Code: 0, Value: 10 [ 4776.893138] evbug.c: Event. Dev: input16, Type: 0, Code: 0, Value: 0 [ 4776.893144] evbug.c: Event. Dev: input16, Type: 3, Code: 1, Value: 765 [ 4776.893148] evbug.c: Event. Dev: input16, Type: 0, Code: 0, Value: 0 [ 4778.729711] evbug.c: Event. Dev: input16, Type: 0, Code: 0, Value: 1 [ 4778.745506] evbug.c: Disconnected device: input16 -
Asain Kujovic about 9 yearshey, i have same problem as your question, can you explain better what is your conclusions please. can uinput device be REL and ABS for example... GDM is ok with that but X not. is there a link where you find out usefull things about this
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Alex over 8 years@AsainKujovic see doc/Documentation/input/event-codes.txt much more clear, ABS are events like touch screen tap, probably (have to check) X on mice listen for REL only (how could a mouse send an abs event if it doesn't know the screen resolution)
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S.I.J over 8 years@Alex I have my touch working but can't figure out how to generate click events. Can you please tell me how should I do that.
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Alex over 8 years@ShaheenIquebal I can't tell but here's some old link which hopefully may help you, old stuff but should still work: input26/udpmouse docs input, input26 (Italian)
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S.I.J over 8 years@Alex Thanks, will have a look
