linux-kernel - Re: [PATCH 2/9] tty: n_gsm: add restart parameter to DLC specific ioctl config

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Date:   Wed, 5 Apr 2023 11:15:47 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "D. Starke" <daniel.starke@...mens.com>
cc:     linux-serial <linux-serial@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/9] tty: n_gsm: add restart parameter to DLC specific
 ioctl config

On Wed, 5 Apr 2023, D. Starke wrote:

> From: Daniel Starke <daniel.starke@...mens.com>
> 
> 'gsm_config_ext' already allows to force a link reset via 'restart'
> parameter.

Please be more precise, there a function and struct with this name.

HOWEVER, there is no such parameter in tty-next (am I looking from wrong 
repo??):

static int gsm_config_ext(struct gsm_mux *gsm, struct gsm_config_ext *ce)

...nor here:

struct gsm_config_ext {
        __u32 keep_alive;       /* Control channel keep-alive in 1/100th of a
                                 * second (0 to disable)
                                 */
        __u32 wait_config;      /* Wait for DLCI config before opening virtual link? */
        __u32 reserved[6];      /* For future use, must be initialized to zero */
};

???


-- 
 i.

> An equivalent parameter for an forced channel reset is still
> missing in 'gsm_dlci_config'. Therefore, the user has no means to perform
> an automatic channel reset after parameter configuration for
> non-conflicting changes. Conflicting changes automatically reset the
> channel already in the current implementation.
> 
> Add the parameter 'restart' to 'gsm_dlci_config' to force a channel reset
> after ioctl setting regardless of whether the changes made require this or
> not.
> 
> Note that the parameter is limited to the values 0 and 1 to allow future
> additions here.
> 
> Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
> ---
>  drivers/tty/n_gsm.c         | 4 ++++
>  include/uapi/linux/gsmmux.h | 3 ++-
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index c42c8b89fd46..eb21ca583642 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -2531,6 +2531,8 @@ static int gsm_dlci_config(struct gsm_dlci *dlci, struct gsm_dlci_config *dc, in
>  		return -EINVAL;
>  	if (dc->k > 7)
>  		return -EINVAL;
> +	if (dc->restart > 1)   /* allow future extensions */
> +		return -EINVAL;
>  
>  	/*
>  	 * See what is needed for reconfiguration
> @@ -2545,6 +2547,8 @@ static int gsm_dlci_config(struct gsm_dlci *dlci, struct gsm_dlci_config *dc, in
>  	/* Requires care */
>  	if (dc->priority != dlci->prio)
>  		need_restart = true;
> +	if (dc->restart)
> +		need_restart = true;
>  
>  	if ((open && gsm->wait_config) || need_restart)
>  		need_open = true;
> diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
> index eb67884e5f38..33ee7b857c52 100644
> --- a/include/uapi/linux/gsmmux.h
> +++ b/include/uapi/linux/gsmmux.h
> @@ -58,7 +58,8 @@ struct gsm_dlci_config {
>  	__u32 priority;		/* Priority (0 for default value) */
>  	__u32 i;		/* Frame type (1 = UIH, 2 = UI) */
>  	__u32 k;		/* Window size (0 for default value) */
> -	__u32 reserved[8];	/* For future use, must be initialized to zero */
> +	__u32 restart;		/* Force DLCI channel reset? */
> +	__u32 reserved[7];	/* For future use, must be initialized to zero */
>  };
>  
>  #define GSMIOC_GETCONF_DLCI	_IOWR('G', 7, struct gsm_dlci_config)
>