linux-kernel - Re: [PATCH v6 1/9] tty: n_gsm: add restart flag to DLC specific ioctl config

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Message-ID: <2023082227-morse-dreaded-4cd5@gregkh>
Date:   Tue, 22 Aug 2023 15:05:44 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "D. Starke" <daniel.starke@...mens.com>
Cc:     linux-serial@...r.kernel.org, jirislaby@...nel.org,
        ilpo.jarvinen@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/9] tty: n_gsm: add restart flag to DLC specific
 ioctl config

On Tue, Aug 22, 2023 at 03:05:10PM +0200, Greg KH wrote:
> On Thu, Aug 17, 2023 at 11:32:23AM +0200, D. Starke wrote:
> > From: Daniel Starke <daniel.starke@...mens.com>
> > 
> > Currently, changing the parameters of a DLCI gives no direct control to the
> > user whether this should trigger a channel reset or not. The decision is
> > solely made by the driver based on the assumption which parameter changes
> > are compatible or not. Therefore, the user has no means to perform an
> > automatic channel reset after parameter configuration for non-conflicting
> > changes.
> > 
> > Add the parameter 'flags' to 'gsm_dlci_config' to force a channel reset
> > after ioctl setting regardless of whether the changes made require this or
> > not by setting this to 'GSM_FL_RESTART'.
> > 
> > Note that 'GSM_FL_RESTART' is currently the only allow flag to allow
> > additions here.
> > 
> > Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
> > ---
> >  drivers/tty/n_gsm.c         |  4 ++++
> >  include/uapi/linux/gsmmux.h | 15 ++++++++++++++-
> >  2 files changed, 18 insertions(+), 1 deletion(-)
> > 
> > v5 -> v6:
> > No changes.
> > 
> > Link: https://lore.kernel.org/all/20230517155704.5701-1-daniel.starke@siemens.com/
> > 
> > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> > index 42759500b79e..a4268515920e 100644
> > --- a/drivers/tty/n_gsm.c
> > +++ b/drivers/tty/n_gsm.c
> > @@ -2532,6 +2532,8 @@ 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->flags & ~GSM_FL_RESTART)   /* allow future extensions */
> > +		return -EINVAL;
> >  
> >  	/*
> >  	 * See what is needed for reconfiguration
> > @@ -2546,6 +2548,8 @@ 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->flags & GSM_FL_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..e56e2d7ea6eb 100644
> > --- a/include/uapi/linux/gsmmux.h
> > +++ b/include/uapi/linux/gsmmux.h
> > @@ -2,10 +2,22 @@
> >  #ifndef _LINUX_GSMMUX_H
> >  #define _LINUX_GSMMUX_H
> >  
> > +#include <linux/const.h>
> >  #include <linux/if.h>
> >  #include <linux/ioctl.h>
> >  #include <linux/types.h>
> >  
> > +/*
> > + * flags definition for n_gsm
> > + *
> > + * Used by:
> > + * struct gsm_dlci_config.flags
> > + */
> > +/* Forces a DLCI reset if set. Otherwise, a DLCI reset is only done if
> > + * incompatible settings were provided. Always cleared on retrieval.
> > + */
> > +#define GSM_FL_RESTART	_BITUL(0)
> > +
> >  struct gsm_config
> >  {
> >  	unsigned int adaption;
> > @@ -58,7 +70,8 @@ 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 flags;		/* DLCI specific flags. */
> 
> This should be called "dlci_flags" right?  Otherwise when you add more
> flags in the reserved area, what will you call them?

Oh nevermind, the name of the structure has it there, this is fine, I'll
take this...

thanks,

greg k-h