linux-kernel - Re: [RFC PATCH 1/5] watchdog: Add API to trigger reboots

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Message-ID: <53639C1C.8050701@roeck-us.net>
Date:	Fri, 02 May 2014 06:22:36 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Will Deacon <will.deacon@....com>
CC:	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Arnd Bergmann <arnd@...db.de>,
	Russell King <linux@....linux.org.uk>,
	Jonas Jensen <jonas.jensen@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/5] watchdog: Add API to trigger reboots

On 05/02/2014 03:01 AM, Will Deacon wrote:
> Hi Guenter,
>
> This looks pretty sensible to me (and the arm/arm64 bits look fine too), but
> I have one question below...
>
> On Thu, May 01, 2014 at 04:41:29PM +0100, Guenter Roeck wrote:
>> Some hardware implements reboot through its watchdog hardware,
>> for example by triggering a watchdog timeout. Platform specific
>> code starts to spread into watchdog drivers, typically by setting
>> pointers to a callback functions which is then called from the
>> platform reset handler.
>>
>> To simplify code and provide a unified API to trigger reboots by
>> watchdog drivers, provide a single API to trigger such reboots
>> through the watchdog subsystem.
>>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>>   drivers/watchdog/watchdog_core.c |   17 +++++++++++++++++
>>   include/linux/watchdog.h         |   11 +++++++++++
>>   2 files changed, 28 insertions(+)
>>
>> diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
>> index cec9b55..4ec6e2f 100644
>> --- a/drivers/watchdog/watchdog_core.c
>> +++ b/drivers/watchdog/watchdog_core.c
>> @@ -43,6 +43,17 @@
>>   static DEFINE_IDA(watchdog_ida);
>>   static struct class *watchdog_class;
>>
>> +static struct watchdog_device *wdd_reboot_dev;
>> +
>> +void watchdog_do_reboot(enum reboot_mode mode, const char *cmd)
>> +{
>> +	if (wdd_reboot_dev) {
>> +		if (wdd_reboot_dev->ops->reboot)
>> +			wdd_reboot_dev->ops->reboot(wdd_reboot_dev, mode, cmd);
>> +	}
>> +}
>
> What reboot_mode values would you expect a watchdog to support other than
> REBOOT_HARD? Also, is the cmd even useful here?
>

Answer is "I don't know" in both cases. I thought about dropping the parameters,
but then I thought it does not hurt to have them around either. I am open to
suggestions and to dropping the parameters if everyone agrees that they are
useless.

Guenter

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