Home Page Forums MAME Non-Windows MAME Support Using a second keyboard as a joystick on linux

locate input-event-codes.h
less /usr/src/linux-headers-5.4.0-67/include/uapi/linux/input-event-codes.h

#define BTN_MISC                0x100
#define BTN_0                   0x100
#define BTN_1                   0x101
#define BTN_2                   0x102
#define BTN_3                   0x103
#define BTN_4                   0x104
#define BTN_5                   0x105
#define BTN_6                   0x106
#define BTN_7                   0x107
#define BTN_8                   0x108
#define BTN_9                   0x109

#define BTN_DPAD_UP             0x220
#define BTN_DPAD_DOWN           0x221
#define BTN_DPAD_LEFT           0x222
#define BTN_DPAD_RIGHT          0x223

#define BTN_TRIGGER_HAPPY               0x2c0
#define BTN_TRIGGER_HAPPY1              0x2c0
...
#define BTN_TRIGGER_HAPPY40             0x2e7

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/uinput.h>
#include <stdlib.h>

#define msleep(ms) usleep((ms)*1000)

static void setup_abs(int fd, unsigned chan, int min, int max);  


// demo showing how to provide a joystick/gamepad instance from
// userspace.

int main(void)
{ 
  int fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
  
  if (fd < 0)
    {
      perror("open /dev/uinput");
      return 1;
    }

  ioctl(fd, UI_SET_EVBIT, EV_KEY); // enable button/key handling

int translatetable[] = { 

KEY_LEFTSHIFT, BTN_0,
KEY_Z, BTN_1,
KEY_X, BTN_2,
KEY_C, BTN_3,
KEY_V, BTN_4,
KEY_B, BTN_5,
KEY_N, BTN_6,
KEY_M, BTN_7,
KEY_COMMA, BTN_8,
KEY_DOT, BTN_9,
KEY_SLASH, BTN_TRIGGER_HAPPY1,
KEY_RIGHTSHIFT, BTN_TRIGGER_HAPPY2,
KEY_UP, BTN_DPAD_UP,
KEY_LEFT, BTN_DPAD_LEFT,
KEY_DOWN, BTN_DPAD_DOWN,
KEY_RIGHT, BTN_DPAD_RIGHT };

int translatetablelen = sizeof(translatetable) / sizeof (int);

int rcode; 


// tell uinput which BTN events we will generate
for (int i=0;i<translatetablelen;i+=2)     ioctl(fd, UI_SET_KEYBIT, translatetable[i+1]);

 char keyboard_to_open[256] = "/dev/input/by-id/usb-0461_USB_Wired_Keyboard-event-kbd";
 char keyboard_name[256] = "Unknown";
 
 int keyboard_fd = open(keyboard_to_open, O_RDONLY | O_NONBLOCK);  


  if ( keyboard_fd == -1 ) {
    printf("Failed to open keyboard.\n");
    exit(1);
  }
  rcode = ioctl(keyboard_fd, EVIOCGNAME(sizeof(keyboard_name)), keyboard_name);
  printf("Reading From : %s \n", keyboard_name);

  printf("Getting exclusive access: ");
  rcode = ioctl(keyboard_fd, EVIOCGRAB, 1);
  printf("%s\n", (rcode == 0) ? "SUCCESS" : "FAILURE");
  struct input_event keyboard_event;


  ioctl(fd, UI_SET_EVBIT, EV_ABS); // enable analog absolute position handling
  
  setup_abs(fd, ABS_X,  -512, 512);
  setup_abs(fd, ABS_Y,  -512, 512);
  setup_abs(fd, ABS_Z,  -32767, 32767);
  
  struct uinput_setup setup =
    {
     .name = "Userspace Joystick",
     .id =
     {
      .bustype = BUS_USB,
      .vendor  = 0x3,
      .product = 0x3,
      .version = 2,
     }
    };

  if (ioctl(fd, UI_DEV_SETUP, &setup))
    {
      perror("UI_DEV_SETUP");
      return 1;
    }
  
  if (ioctl(fd, UI_DEV_CREATE))
    {
      perror("UI_DEV_CREATE");
      return 1;
    }


struct input_event button_event;
while (1) {      
      int readval;
      
      if ( readval = read(keyboard_fd, &keyboard_event, sizeof(keyboard_event)), readval != -1 ) {
      	if (keyboard_event.type == EV_KEY)
      		for (int i=0;i<translatetablelen;i+=2) if (keyboard_event.code == translatetable[i]) 
      					{
						button_event.type = EV_KEY;
						button_event.code = translatetable[i+1];
						button_event.value = keyboard_event.value;
						
						  printf("ev type = %d keycode=%d code = %d value = %d\n",
						  	button_event.type,
						  	keyboard_event.code,
							button_event.code,
							button_event.value); 
	
					  if(write(fd, &button_event, sizeof button_event) < 0)
							{
							  perror("write");
							  return 1;
							}
						// send a SYNC event
						button_event.type = EV_SYN;
						button_event.code = 0;
						button_event.value = 0;

	
					  if(write(fd, &button_event, sizeof button_event) < 0)
							{
							  perror("write");
							  return 1;
							}
	
					  if(write(fd, &button_event, sizeof button_event) < 0)
							{
							  perror("write");
							  return 1;
							}
						break;
					}    														
 	if (readval == -1) msleep(50);
    }
}


  if(ioctl(fd, UI_DEV_DESTROY))
    {
      printf("UI_DEV_DESTROY");
      return 1;
    }

  close(fd);
  return 0;
}


// enable and configure an absolute "position" analog channel

static void setup_abs(int fd, unsigned chan, int min, int max)
{
  if (ioctl(fd, UI_SET_ABSBIT, chan))
    perror("UI_SET_ABSBIT");
  
  struct uinput_abs_setup s =
    {
     .code = chan,
     .absinfo = { .minimum = min,  .maximum = max },
    };

  if (ioctl(fd, UI_ABS_SETUP, &s))
    perror("UI_ABS_SETUP");
}