On Fri, Jul 10, 2020 at 10:46:19AM +0000, Joakim Tjernlund wrote: > On Fri, 2020-07-10 at 12:34 +0200, Greg KH wrote: > > > > On Fri, Jul 10, 2020 at 11:35:18AM +0200, Joakim Tjernlund wrote: > > > tty_set_operations(acm_tty_driver, &acm_ops); > > > > > > - retval = tty_register_driver(acm_tty_driver); > > > + retval = usb_register(&acm_driver); > > > if (retval) { > > > put_tty_driver(acm_tty_driver); > > > return retval; > > > } > > > > > > - retval = usb_register(&acm_driver); > > > + retval = tty_register_driver(acm_tty_driver); > > > if (retval) { > > > - tty_unregister_driver(acm_tty_driver); > > > + usb_deregister(&acm_driver); > > > > Why are you switching these around? I think I know, but you don't > > really say... > > I wrote: > For initial termios to reach USB core, USB driver has to be > registered before TTY driver. > Found out that by trial and error. Isn't that clear enough? No, that makes no sense at all since USB core does not care about init_termios. Johan