linux-kernel - Re: [PATCH v3] watchdog: Add hook for kicking in kdump path

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Date:	Tue, 28 May 2013 08:34:52 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Wim Van Sebroeck <wim@...ana.be>
Cc:	Don Zickus <dzickus@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-watchdog@...r.kernel.org, kexec@...ts.infradead.org,
	LKML <linux-kernel@...r.kernel.org>, vgoyal@...hat.com,
	dyoung@...hat.com
Subject: Re: [PATCH v3] watchdog: Add hook for kicking in kdump path

On Mon, May 27, 2013 at 09:16:18PM +0200, Wim Van Sebroeck wrote:
>  Hi Guenter,
> 
> > > Hi Guenter,
> > > 
> > > Is there an easy way to determine which driver is loaded for each
> > > /dev/watchdogN device (from a script perspective).
> > > 
> > > Basically, I wanted to determine the module that needs to be included in
> > > the kdump initrd image.
> > > 
> > Sometimes. For example, the iTCO_wdt driver has an entry in /sys/devices, and
> > /sys/class/watchdog/watchdogX/device points to it. That is not always the case,
> > howewver. In my system, for example, the MEI watchdog is active, but there is
> > nothing I can find that would give me an indication that /dev/watchdog0 actually
> > points to the MEI watchdog driver.
> > 
> > Of course I might be missing something, and there might be some other means
> > to identify the driver from userspace. Would be great, actually, as I am having
> > the same problem.
> 
> Only when you set the .parent field in the watchdog_device data you will get the
> referal in the /sys/class/... tree. In iTCO_wdt.c you have the following code
> that does that: iTCO_wdt_watchdog_dev.parent = dev->dev.parent;
> 
> From the watchdog-kernel-api documentation:
> * parent: set this to the parent device (or NULL) before calling
>   watchdog_register_device.
> 
Hi Wim,

unfortunately that only works if the driver is instantiated as platform driver,
PCI driver, or similar, where a parent device exists. Some drivers are, however,
instantiated directly from the init function (the BookE driver is an example).
What is the recommended action in this case ? Convert it to a platform driver ?

Thanks,
Guenter
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