Date: Tue, 8 Mar 2016 12:55:59 -0800
From: Eduardo Valentin <edubezval@gmail.com>
To: Leo Yan <leo.yan@linaro.org>
Cc: Javi Merino <javi.merino@arm.com>, Wei Xu <xuwei5@hisilicon.com>,
        Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>, Zhang Rui <rui.zhang@intel.com>,
        kongxinwei <kong.kongxinwei@hisilicon.com>,
        Punit Agrawal <Punit.Agrawal@arm.com>,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH v2 1/5] thermal: change "hysteresis" as optional property
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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.

BR,

> 
> Thanks,
> Leo Yan