How to get HP laptop Toggle Touchpad key to work

wildstar84 · posted: 2016-04-26 07:14

I purchased a new (refurbished) HP"Elitebook" 8440p laptop. Installed Antix remastered, of course! Got all the special HP light-up buttons above the keyboard working with xbindkeys EXCEPT the one that looks like a tiny touchpad, that's supposed to toggle the touchpad. That little bugger just did not want to work, not even in Windows-7?! Finally stole and hacked up a tiny daemon C program that DOES make it work! You need to do the following:

1) in rc.local or somewhere in startup scripts add: /usr/bin/setkeycodes e058 140
2) compile this little C program"keycheckd" (gcc -o keycheckd keycheckd.c) and place the compiled binary in /usr/local/bin/, and chown 4755 keycheckd
3) In your X desktop session's startup script do (must be started from w/n X desktop, NOT startup or console!):

Code: Select all

xset -r 138 -r 140 -r 146 -r 148
keycheckPid=`pidof keycheckd`;
if [["X$keycheckPid" =="X" ]]; then
    /usr/bin/nice -n 10 /usr/local/bin/keycheckd &
fi

The source (keycheckd.c) (note: you could add other keysyms / actions, if needed):

Code: Select all

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

/*
   JWT:THIS DAEMON PGM WATCHES THE KEYBOARD FOR PRESSES OF THE SPECIAL HP ELITEBOOK 8440P"TOGGLE-KEYPAD" 
   KEY WHICH X (xev, xbindkey & FRIENDS REFUSE TO SEE AFTER THE 1ST PRESS PER REBOOT) AND INVOKES THE 
   COMMAND TO TOGGLE THE TOUCHPAD (AS IT WAS DESIGNED TO DO).  X DOESNPT LIKE THIS SPECIAL KEY B/C IT 
   ONLY SENDS A"KeyPressed" EVENT W/NO CORRESPONDING"KeyReleased" EVENT.  IT WORKS LIKE OTHER"LED"DED 
   KEYS SUCH AS CAPSLOCK AND NUMLOCK!  THE INITIAL STATE IS"BLUE" (TOUCHPAD ON), FIRST PRESS SENDS 
   KEYCODE 140 (148 TO xbindkeys) AND SWITCHES THE LED TO"ORANGE".  NEXT PRESS SENDS KEYCODE 138 (146)
   AND SWITCHES THE LED BACK TO"BLUE".  SUBSEQUENT KEYPRESSES ALTERNATE BETWEEN THESE TWO STATES. 

   I STOLE THIS PGM. FROM HERE:  http://stackoverflow.com/questions/20943322/accessing-keys-from-linux-input-device
   I MODIFIED IT TO ONLY CARE A/B THESE TWO KEYCODES.  NOTE:  I HAD TO ADD"setkeycodes e058 140" TO 
   rc_local.pl WHEREAS THE OTHER ONE (138) WAS ALREADY RECOGNIZED BY THE KERNEL.  THIS PROGRAM SHOULD BE 
   STARTED THE FIRST TIME AFTERSTEP STARTS UP (.afterstep/autoexec)
*/

int main(void)
{
    const char *dev ="/dev/input/by-path/platform-i8042-serio-0-event-kbd";
    struct input_event ev;
    ssize_t n;
    int fd;

    fd = open(dev, O_RDONLY);
    if (fd == -1) {
        fprintf(stderr,"Cannot open %s: %s.\n", dev, strerror(errno));
        return EXIT_FAILURE;
    }
    while (1) {
        n = read(fd, &ev, sizeof ev);
        if (n == (ssize_t)-1) {
            if (errno == EINTR)
                continue;
            else
                break;
        } else
        if (n != sizeof ev) {
            errno = EIO;
            break;
        }
        if (ev.type == EV_KEY && ev.value >= 0 && ev.value <= 2) {
/* printf("0x%04x (%d)\n", (int)ev.code, (int)ev.code); */
            if ((int)ev.code == 138) {
                /* TURN ON TOUCHPAD: */
/* printf("--138: turn touchpad ON!\n"); */
                system ("/usr/bin/synclient TouchpadOff=0");
            } else if ((int)ev.code == 140) {
                /* TURN OFF TOUCHPAD: */
/* printf("--140: turn touchpad off!\n"); */
                system ("/usr/bin/synclient TouchpadOff=1");
            }
        }
    }
    fflush(stdout);
    fprintf(stderr,"%s.\n", strerror(errno));
    return 0;
}

Now, when you press this"key", it should turn orange and actually disable your touchpad, a second press should turn it back blue and re-enable your touchpad. I believe you could add the"/usr/bin/synclient TouchpadOff=1" in your X session startup script above where you start this daemon, and reverse the two"TouchpadOff=#" commands in it to have it start out disabled, then toggle to enabled, then disabled, etc.

Hope someone else finds this hack useful!

Jim