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

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Jul 10, 2020 at 11:35:18AM +0200, Joakim Tjernlund wrote:
> BO will disable USB input until the device opens. This will
> avoid garbage chars waiting flood the TTY. This mimics a real UART
> device better.
> For initial termios to reach USB core, USB driver has to be
> registered before TTY driver.

You are doing two different things here, please break this up into 2
patches, with good documentation for both of them.

And any reason you didn't send this to the people listed in
scripts/get_maintainers.pl when run on this patch?

> 
> Signed-off-by: Joakim Tjernlund <joakim.tjernlund@infinera.com>
> Cc: stable@vger.kernel.org
> ---
> 
>  I hope this change makes sense to you, if so I belive
>  ttyUSB could do the same.
> 
>  drivers/usb/class/cdc-acm.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
> index 751f00285ee6..5680f71200e5 100644
> --- 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;

Huh?  Are you sure this works?

>  	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...

thanks,

greg k-h