bad address error

[MusicMaker]

Whenever trying to send/recive data (for example amidi) a "Bad address' error is returned. The reason the the following call faila.

// select N_TTY line discipline (for sure)
ldisc = N_TTY;
if ((retval = ioctl_tty(serial->file, TIOCSETD, (unsigned long)&ldisc)) < 0) {
snd_printk(KERN_ERR "TIOCSETD (N_TTY) failed for tty %s\n", serial->sdev);
goto __end;
}
When this code is removed, amidi can connect the port but it causes an kernel crash and hangs up the MIDI sub system

[990.262157] RIP: 0010:snd_serialmidi_output_trigger+0x58/0x140 [snd_serialmidi]

only a reboot can kill the processes. Proably the cause is due to ldisc = tty->ldisc not being set.

Ubuntu 20.10