On Thu, Nov 30, 2023 at 02:09:48PM +0100, Oliver Neukum wrote:
> Hi,
>
> it seems inconsistent. The tty layer
> in drivers/tty/tty_io.c::send_break()
>
> static int send_break(struct tty_struct *tty, unsigned int duration)
> {
> int retval;
>
> if (tty->ops->break_ctl == NULL)
> return 0;
>
> not supporting break_ctl() is treated as the operation
> succeeding. Yet in drivers/usb/serial/usb-serial.c::serial_break()
>
> static int serial_break(struct tty_struct *tty, int break_state)
> {
> struct usb_serial_port *port = tty->driver_data;
>
> dev_dbg(&port->dev, "%s\n", __func__);
>
> if (port->serial->type->break_ctl)
> return port->serial->type->break_ctl(tty, break_state);
>
> return -ENOTTY;
> }
>
> we are seeing that not supporting break_ctl() leads to returning
> -ENOTTY, which drivers/tty/tty_io.c::send_break() will return to user space.
> These reactions are at odds with each other. What is a driver supposed
> to do?
usb-serial should probably change, but given the fact that no one has
noticed this in the 20+ years it has been like this, is it really
needed? :)
thanks,
greg k-h
