Re: [PATCH v2] tty: n_gsm: delete SABM command frame as requester

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jul 01, 2021 at 07:27:20PM +0800, Zhenguo Zhao wrote:
> From: Zhenguo Zhao <Zhenguo.Zhao1@unisoc.com>
> 
> as initiator,it need to send SABM command ,as requester,there is
> no need to send the SABM control frame,it will cause redundant data.

Same issue here with this text.  Please work on fixing it up to be
understood by others better.

> 
> Signed-off-by: Zhenguo Zhao <Zhenguo.Zhao1@unisoc.com>
> ---
>  drivers/tty/n_gsm.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 5fea02c..41a6501 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -2997,6 +2997,7 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp)
>  {
>  	struct gsm_dlci *dlci = tty->driver_data;
>  	struct tty_port *port = &dlci->port;
> +	struct gsm_mux *gsm = dlci->gsm;
>  
>  	port->count++;
>  	tty_port_tty_set(port, tty);
> @@ -3005,8 +3006,9 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp)
>  	/* We could in theory open and close before we wait - eg if we get
>  	   a DM straight back. This is ok as that will have caused a hangup */
>  	tty_port_set_initialized(port, 1);
> -	/* Start sending off SABM messages */
> -	gsm_dlci_begin_open(dlci);
> +	/* Start sending off SABM messages for initiator */
> +	if (gsm->initiator)
> +		gsm_dlci_begin_open(dlci);

Why is this only an issue for initiators?  And why has no one reported
this problem before now?

Do you not also need to make ths same change somewhere else when
shutting down?

thanks,

greg k-h