linux-kernel - Re: [PATCH 67/68] TTY: isdn/gigaset, do not set tty->driver

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Date:	Mon, 05 Mar 2012 18:05:52 +0100
From:	Tilman Schmidt <tilman@...p.cc>
To:	Jiri Slaby <jslaby@...e.cz>
CC:	gregkh@...uxfoundation.org, alan@...ux.intel.com,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	jirislaby@...il.com, Hansjoerg Lipp <hjlipp@....de>,
	gigaset307x-common@...ts.sourceforge.net
Subject: Re: [PATCH 67/68] TTY: isdn/gigaset, do not set tty->driver_data
 to NULL

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Am 05.03.2012 14:52, schrieb Jiri Slaby:
> Close the window in open where driver_data is reset to NULL on each
> open. It could cause other processes to get invalid retval from the
> tty->ops operations because of the checks all over the code.
> 
> With this change we may do other cleanups. Now, the only valid check
> for tty->driver_data != NULL is in close. This can happen only if open
> fails at gigaset_get_cs_by_tty or try_module_get. The rest of checks
> in various tty->ops->* are invalid as driver_data cannot be NULL
> there. The same holds for cs->open_count. So remove them.

Thanks for that nice cleanup. It's most welcome.
Just one question and a small nit:

> --- a/drivers/isdn/gigaset/interface.c
> +++ b/drivers/isdn/gigaset/interface.c
[...]
> @@ -178,12 +176,11 @@ static int if_open(struct tty_struct *tty, struct file *filp)
>  
>  static void if_close(struct tty_struct *tty, struct file *filp)
>  {
> -	struct cardstate *cs;
> +	struct cardstate *cs = tty->driver_data;
>  	unsigned long flags;
>  
> -	cs = (struct cardstate *) tty->driver_data;
> -	if (!cs) {
> -		pr_err("%s: no cardstate\n", __func__);
> +	if (!cs) { /* happens if we didn't find cs in open */
> +		printk(KERN_DEBUG "%s: no cardstate\n", __func__);
>  		return;
>  	}
>  

Why are you downgrading the error message from KERN_ERR to KERN_DEBUG
here? I would think that condition would warrant a message with
KERN_ERR severity.
Also, the driver does KERN_DEBUG output uniformly through the gig_dbg
macro, so if you are sure it should be turned into a debug message
then please write it as

	gig_dbg(DEBUG_IF, "%s: no cardstate", __func__);

like four lines later.

Thanks,
Tilman

- -- 
Tilman Schmidt                    E-Mail: tilman@...p.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)
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