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From: Corey Minyard <cminyard@mvista.com>
To: Jerry Hoemann <jerry.hoemann@hpe.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	Convert@minyard.net, the@minyard.net, IPMI@minyard.net,
	watchdog@minyard.net, to@minyard.net, standard@minyard.net,
	interface@minyard.net, linux-watchdog@vger.kernel.org,
	Wim Van Sebroeck <wim@linux-watchdog.org>
Subject: Re: [PATCH 02/12] watchdog: Add the ability to provide data to read
Date: Tue, 20 Aug 2019 07:12:44 -0500
Message-ID: <20190820121243.GO445@minyard.net> (raw)
In-Reply-To: <20190820010946.GF25435@anatevka.americas.hpqcorp.net>

On Mon, Aug 19, 2019 at 07:09:46PM -0600, Jerry Hoemann wrote:
> On Mon, Aug 19, 2019 at 07:23:09PM -0500, Corey Minyard wrote:
> > On Mon, Aug 19, 2019 at 03:43:45PM -0700, Guenter Roeck wrote:
> > > On Mon, Aug 19, 2019 at 03:37:01PM -0500, minyard@acm.org wrote:
> > > > From: Corey Minyard <cminyard@mvista.com>
> > > > 
> > > > This is for the read data pretimeout governor.
> > > > 
> > > > Signed-off-by: Corey Minyard <cminyard@mvista.com>
> > > 
> > > On further thought, I think it would be a bad idea to add this
> > > functionality: It changes the userspace ABI for accessing the watchdog
> > > device. Today, when a watchdog device is opened, it does not provide
> > > read data, it does not hang, and returns immediately. A "cat" from it
> > > is an easy and quick means to test if a watchdog works.
> > 
> > Umm, why would a "cat" from a watchdog tell you if a watchdog works?
> 
> cat /dev/watchdog starts the watchdog running.
> 
> Then one can do useful things like monitor /sys/class/watchdog/watchdogN and see
> time ticking down, etc..,
> 
> echo V > /dev/watchdog stops the watchdog assuming driver supports WDIOF_MAGICCLOSE.
> 
> So I can test without having to reboot.
> 
> One can't test magic close with the proposed change as /dev/watchdog
> is exclusive open.

Sure you can:

# echo "" >/dev/watchdog0
[   92.390649] watchdog: watchdog0: watchdog did not stop!
# sleep 2
# cat /sys/class/watchdog/watchdog0/timeleft
8
# echo "V" >/dev/watchdog0

Works just fine.  But I can make it so that reading returns an error
unless the governor is the read one.

The question is if this is required to transfer the IPMI watchdog
over to the standard interface.  It currently has this function,
do we do an API change to move it over?

-corey

> 
> 
> 
> 
> -- 
> 
> -----------------------------------------------------------------------------
> Jerry Hoemann                  Software Engineer   Hewlett Packard Enterprise
> -----------------------------------------------------------------------------

  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190819203711.32599-1-minyard@acm.org>
2019-08-19 20:37 ` [PATCH 01/12] watchdog: NULL the default governor if it is unregistered minyard
2019-08-19 22:35   ` Guenter Roeck
2019-08-19 20:37 ` [PATCH 02/12] watchdog: Add the ability to provide data to read minyard
2019-08-19 21:50   ` Guenter Roeck
2019-08-19 22:43   ` Guenter Roeck
2019-08-20  0:23     ` Corey Minyard
2019-08-20  1:09       ` Jerry Hoemann
2019-08-20 12:12         ` Corey Minyard [this message]
2019-08-20 13:53           ` Guenter Roeck
2019-08-20 15:58             ` Corey Minyard
2019-08-20 17:14               ` Guenter Roeck
2019-08-20 18:16                 ` Corey Minyard
2019-08-19 20:37 ` [PATCH 03/12] watchdog: Add a pretimeout governor to provide read data minyard
2019-08-19 20:37 ` [PATCH 04/12] watchdog: Allow pretimeout governor setting to be accessed from modules minyard
2019-08-19 21:49   ` Guenter Roeck
2019-08-20  0:24     ` Corey Minyard
2019-08-19 20:37 ` [PATCH 05/12] watchdog:ipmi: Move the IPMI watchdog to drivers/watchdog minyard
2019-08-19 20:37 ` [PATCH 06/12] watchdog:ipmi: Convert over to the standard watchdog infrastructure minyard
2019-08-19 20:37 ` [PATCH 07/12] watchdog:ipmi: Add the ability to fetch the current time left minyard
2019-08-19 20:37 ` [PATCH 08/12] watchdog: Add the ability to set the action of a timeout minyard
2019-08-19 21:58   ` Guenter Roeck
2019-08-20  0:39     ` Corey Minyard
2019-08-20 14:17       ` Guenter Roeck
2019-08-20 19:39         ` Corey Minyard
2019-08-19 20:37 ` [PATCH 09/12] watchdog:ipmi: Implement action and preaction functions minyard
2019-08-19 20:37 ` [PATCH 10/12] watchdog: Add a way to set the governor through the ioctl minyard
2019-08-19 20:37 ` [PATCH 11/12] watchdog: Add a sample program that can fully use the watchdog interface minyard
2019-08-19 20:37 ` [PATCH 12/12] watchdog: Set the preaction fields for drivers supporting pretimeout minyard

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