linux-kernel - Re: [PATCH v2 3/4] power: Add support for DA9150 Fuel-Gauge

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Date:	Tue, 7 Jul 2015 07:58:01 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	"Opensource [Adam Thomson]" <Adam.Thomson.Opensource@...semi.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	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>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Support Opensource <Support.Opensource@...semi.com>,
	jic23@....ac.uk
Subject: Re: [PATCH v2 3/4] power: Add support for DA9150 Fuel-Gauge

On Mon, 06 Jul 2015, Opensource [Adam Thomson] wrote:

> On July 3, 2015 16:22, Lee Jones wrote:
> 
> > > +/*
> > > + * Function template to provide battery temperature. Should provide
> > > + * 0.1 degrees C resolution return values.
> > > + */
> > > +typedef int (*da9150_read_temp_t)(void *context);
> > > +
> > > +/* Register temp callback function */
> > > +void da9150_fg_register_temp_cb(struct power_supply *psy,
> > da9150_read_temp_t cb,
> > > +				void *cb_context);
> > > +
> > >  #endif /* __DA9150_FG_H */
> > 
> > I still don't get why you think pointers are better than just calling
> > the function directly.  Can the *fn() ever point to different functions?
> 
> Here, the intention is to cover the scenario where a battery has no internal
> thermistor, and cannot provide temperature readings to the DA9150 device. In
> that scenario I've allowed for the option of providing an external function
> which can give the temperature reading instead as DA9150 will not be able to
> provide a correct reading in that scenario. This would be platform dependent and
> such a platform using a battery not employing an NTC in their battery can
> register its own call-back function to provide battery temperature instead.
> 
> So, in answer to your question, yes.

Before you add this scenario, I would like to see the code which
utilises it.  I'm not a fan of coding-up 'just-in-case's.  Please
re-submit when you have a user in the same patch-set.

This whole idea will need a discussion with Jonathan (the IIO
Maintainer), now CC'ed.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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