linux-kernel - Re: [PATCH 0/2] DS1374 Watchdog fixes

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Date:   Tue, 25 Apr 2017 14:05:27 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Moritz Fischer <mdf@...nel.org>
Cc:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Moritz Fischer <moritz.fischer@...us.com>,
        linux-watchdog@...r.kernel.org, wim@...ana.be,
        a.zummo@...ertech.it, rtc-linux@...glegroups.com,
        alex.williams@...com
Subject: Re: [PATCH 0/2] DS1374 Watchdog fixes

On Tue, Apr 25, 2017 at 01:34:18PM -0700, Moritz Fischer wrote:
> On Tue, Apr 25, 2017 at 01:22:10PM -0700, Guenter Roeck wrote:
> > On Tue, Apr 25, 2017 at 12:58:36PM -0700, Moritz Fischer wrote:
> > > On Tue, Apr 25, 2017 at 09:58:24AM -0700, Guenter Roeck wrote:
> > > 
> > > > Ah, I missed the "n" in various #ifndef statements.
> > > >
> > > > I can't really comment on how to solve that; I simply don't know.
> > > > Also, even with a dt property, it still would be necessary to have
> > > > a non-DT means to configure one or the other. Making whatever solution
> > > > backward compatible also seems tricky; I don't have a solution for that
> > > > problem either.
> > > 
> > > How does one do these things in a non-dt context? Platform data? I'd let
> > 
> > Platform data is out of favor. You'd probably want to use device properties
> > (see drivers/base/property.c). Question though is if this is considered
> > configuration, hardware description, or both. Presumably the watchdog
> > only makes sense if the reset signal is wired, and the alarm only makes
> > sense if the interrupt is wired, but what if both are wired ?
> 
> To make things worse you can even remap the reset output to the INT pin
> (which my platform does).
> 

So that is what the weird 250ms "interrupt signal" is for. I had wondered
what that is supposed to be used for.

> I'll look at device properties. Thanks for the pointer.
> 
> > 
> > > the MFD select the 'mode'. Maybe being backwards compatible isn't
> > > possible in any case. Is there a rule somewhere that we guarantee you'll
> > > never have to change your CONFIG_FOO options?
> > > 
> > 
> > That would be nice, but no, there is no such rule. You can probably argue
> > that no published kernel configuration enables the watchdog flag,
> > so there is nothing to be concerned about.
> 
> Alright, cool. Thanks
> 
> Moritz
> 
> PS: Haven't forgotten about the cros-ec-hwmon patch that I sent out ...

No, still trying to get internal feedback. I'll have to ask again.

Guenter