linux-kernel - Re: [PATCH v2 06/16] watchdog: hpwdt: drop warning after calling watchdog_init

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Date:   Tue, 16 Apr 2019 14:14:13 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Jerry Hoemann <jerry.hoemann@....com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-watchdog@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/16] watchdog: hpwdt: drop warning after calling
 watchdog_init_timeout

On Tue, Apr 16, 2019 at 10:50:03PM +0200, Wolfram Sang wrote:
> Hi Jerry,
> 
> > I applied patches 1,2 & 6 in testing.
> > 
> > Note, that hpwdt is passing NULL as the third parameter to watchdog_init_timeout().
> > 
> > The second patch in this series is using "dev" as input to dev_err and dev_warn.
> > 
> > This results in the following in dmesg when trying to load hpwdt w/ an invalid soft_margin:
> > 
> > 
> > [   80.848160] (NULL device *): driver supplied timeout (4294967295) out of range
> > [   80.855429] (NULL device *): falling back to default timeout (30)
> 
> Thank you for this report. Yes, using 'dev' blindly is a bug.
> 
> > if the call in hpwdt driver is changed to:
> > 
> > 	if (watchdog_init_timeout(&hpwdt_dev, soft_margin, &dev->dev))
> > 
> > 
> > We see the message like we'd desire:
> > 
> > [ 2061.167100] hpwdt 0000:01:00.0: driver supplied timeout (4294967295) out of range
> > [ 2061.174633] hpwdt 0000:01:00.0: falling back to default timeout (30)
> 
> The above observation makes sense, but I think we should fix the core
> code and not the hpwdt driver. My suggestion would be to add something
> like this to watchdog_init_timeout():
> 
> 	struct device *err_dev = dev ?: wdd->parent;
> 
> And then use err_dev for all the printing. Guenter?
> 

That is a good idea, and we should do that. Unfortunately, wdd->parent can also
be NULL, either because there is no parent device (e.g. softdog.c), or because
the driver author forgot to set ->parent. So we still need a fallback.
Does it make sense to print watchdog_info->identity if both dev and wdd->parent
are NULL ?

Guenter