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

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Message-ID: <54286f3b-98f7-1b7c-8768-2c88ef73e9af@roeck-us.net>
Date:   Wed, 24 Apr 2019 05:57:38 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Wolfram Sang <wsa@...-dreams.de>
Cc:     Jerry Hoemann <jerry.hoemann@....com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Linux Watchdog Mailing List <linux-watchdog@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 06/16] watchdog: hpwdt: drop warning after calling
 watchdog_init_timeout

On 4/24/19 1:38 AM, Geert Uytterhoeven wrote:
> Hi Wolfram,
> 
> On Wed, Apr 17, 2019 at 9:46 PM Wolfram Sang <wsa@...-dreams.de> wrote:
>>> Yes, that works as well. Note that it will actually print something like
>>> "watchdog: <device>: ..." due to the pr_fmt() at the top of watchdog_core.c.
>>> I guess that should be ok.
>>
>> I have the following diff applied on top of patch 2. Works with and
>> without a parent device. I am not super happy casting 'identity' but
>> since its u8-type is exported to userspace, I think we can't avoid it.
>> Guenter, is this cast safe? Here is the diff:
>>
>> diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
>> index cd3ca6b366ef..62be9e52a4de 100644
>> --- a/drivers/watchdog/watchdog_core.c
>> +++ b/drivers/watchdog/watchdog_core.c
>> @@ -115,6 +115,8 @@ static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
>>   int watchdog_init_timeout(struct watchdog_device *wdd,
>>                                  unsigned int timeout_parm, struct device *dev)
>>   {
>> +       const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
>> +                             (const char *)wdd->info->identity;
> 
>      struct watchdog_info {
>              ...
>              __u8  identity[32];     /* Identity of the board */
>      };
> 
> Is identity[] guaranteed to be NUL-terminated?
> 

I would hope so, because we export its contents via sysfs to userspace
with
	return sprintf(buf, "%s\n", wdd->info->identity);

Also, there are already several pr_err() assuming that it is
a string,

Guenter