Mmm.. looks like EMPEG_HIJACK_INJECTBUTTONS explicitly forbids long presses.

I could add an ioctl for it, but at this point I'd rather not.

Your app could instead just do:

fd = open("/proc/empeg_notify", O_RDWR);
write(fd, "button stuff", bytecount);
close(fd);

Not very difficult.

Cheers