linux-kernel - Re: [PATCH v2 1/5] thermal: change "hysteresis" as optional property

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Date:	Wed, 9 Mar 2016 11:10:52 +0000
From:	Javi Merino <javi.merino@....com>
To:	Leo Yan <leo.yan@...aro.org>,
	Eduardo Valentin <edubezval@...il.com>
Cc:	Wei Xu <xuwei5@...ilicon.com>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Zhang Rui <rui.zhang@...el.com>,
	kongxinwei <kong.kongxinwei@...ilicon.com>,
	Punit Agrawal <Punit.Agrawal@....com>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 1/5] thermal: change "hysteresis" as optional property

On Tue, Mar 08, 2016 at 12:55:59PM -0800, Eduardo Valentin wrote:
> On Tue, Mar 08, 2016 at 09:57:43PM +0800, Leo Yan wrote:
> > Hi Eduardo,
> > 
> > On Fri, Mar 04, 2016 at 11:57:53AM +0000, Javi Merino wrote:
> > > On Fri, Mar 04, 2016 at 11:03:49AM +0800, Leo Yan wrote:
> > > > On Thu, Mar 03, 2016 at 08:29:44AM -0800, Eduardo Valentin wrote:
> > > > > On Fri, Feb 26, 2016 at 11:43:43AM +0800, Leo Yan wrote:
> > 
> > [...]
> > 
> > > > > > The property "hysteresis" is mandatory for trip points, so if without
> > > > > > it the thermal zone cannot register successfully. But "hysteresis" is
> > > > > > ignored in the thermal subsystem and only inquired by several thermal
> > > > > > sensor drivers.
> > > > > 
> > > > > If the Linux thermal subsystem has a problem with handling hysteresis, I
> > > > > would rather fix Linux code than relaxing the DT binding. Or if you
> > > > > still believe hysteresis is really optional, I would prefer to see a
> > > > > better justification than "Linux ignores it".
> > > 
> > > I see it the other way round, Is hysteresis a property that, without
> > > it, the thermal code can't configure itself so it fails to create the
> > > trip point?  The current code goes "There is no hysteresis for this
> > > property, I don't know how to set up this trip point!".  I think we
> > > can do better than this.
> > 
> > Do you agree with Javi's suggestion? If you think it's okay, I will
> > move on to send out a new version patch based on Javi's comments.
> 
> No I don't. This discussion so far has been about Linux code. I still
> havent seen an argument explaining why hysteresis has to be optional.

Fair enough.  Looks like I'm holding this driver from being
upstreamed, so I'll back off.

Leo, sorry for misguiding you.  Please bring back the hysteresis
property you had in v1.