Re: [PATCH] cdc-acm: acm_init: Set initial BAUD to B0

[Oliver Neukum <oneukum@suse.de>]

Am Freitag, den 10.07.2020, 11:35 +0200 schrieb Joakim Tjernlund:
> 


Hi,

> --- a/drivers/usb/class/cdc-acm.c
> +++ b/drivers/usb/class/cdc-acm.c
> @@ -1999,19 +1999,19 @@ static int __init acm_init(void)
>  	acm_tty_driver->subtype = SERIAL_TYPE_NORMAL,
>  	acm_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
>  	acm_tty_driver->init_termios = tty_std_termios;
> -	acm_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD |
> +	acm_tty_driver->init_termios.c_cflag = B0 | CS8 | CREAD |
>  								HUPCL | CLOCAL;
>  	tty_set_operations(acm_tty_driver, &acm_ops);
>  
> -	retval = tty_register_driver(acm_tty_driver);
> +	retval = usb_register(&acm_driver);


No,

you cannot do that. This means that probe() is now live.
Probe() in turn does this:

        tty_dev = tty_port_register_device(&acm->port, acm_tty_driver, minor,
                        &control_interface->dev);
        if (IS_ERR(tty_dev)) {
                rv = PTR_ERR(tty_dev);
                goto alloc_fail6;
        }


That is just not a good idea when the tty is not already registered.
You are opening up a race.

	Regards
		Oliver