linux-kernel - Re: [PATCH 3/4] power_supply: Introduce PSE compliant algorithm

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Message-ID: <20140708155614.GA12945@earth.universe>
Date:	Tue, 8 Jul 2014 17:56:14 +0200
From:	Sebastian Reichel <sre@...nel.org>
To:	"Tc, Jenny" <jenny.tc@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	Pavel Machek <pavel@....cz>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	David Woodhouse <dwmw2@...radead.org>,
	David Cohen <david.a.cohen@...ux.intel.com>,
	"Pallala, Ramakrishna" <ramakrishna.pallala@...el.com>
Subject: Re: [PATCH 3/4] power_supply: Introduce PSE compliant algorithm

On Tue, Jul 08, 2014 at 06:07:29AM +0000, Tc, Jenny wrote:
> > > +static int get_tempzone(struct psy_pse_chrg_prof *pse_mod_bprof,
> > > +		int temp)
> > > +{
> > > +	int i = 0;
> > > +	int temp_range_cnt;
> > > +
> > > +	temp_range_cnt =  min_t(u16, pse_mod_bprof->temp_mon_ranges,
> > > +					BATT_TEMP_NR_RNG);
> > > +	if ((temp < pse_mod_bprof->temp_low_lim) ||
> > > +		(temp > pse_mod_bprof->temp_mon_range[0].temp_up_lim))
> > > +		return -EINVAL;
> > > +
> > > +	for (i = 0; i < temp_range_cnt; ++i)
> > > +		if (temp > pse_mod_bprof->temp_mon_range[i].temp_up_lim)
> > > +			break;
> > > +	return i-1;
> > > +}
> > 
> > pse_mod_bprof->temp_mon_ranges > BATT_TEMP_NR_RNG is not allowed, so I
> > suggest to print an error and return some error code.
> > 
> min_t takes care of the upper bound. The algorithm process BATT_TEMP_NR_RNG
> even if the actual number of zones are greater than this.

Right, the function will not fail, but the zone information table is
truncated. I would expect at least warning about that. I think it
doesn't hurt to have a small function, which validates the zone
data as good as possible. Using incorrect temperature zones is a
safety thread and we should try our best to avoid exploding
batteries ;)

Maybe something like that:

static bool check_tempzones(struct psy_pse_chrg_prof *pse_mod_bprof)
{
    int i = 0;
    int last_temp = ;

    /* check size */
    if (BATT_TEMP_NR_RNG > pse_mod_bprof->temp_mon_ranges)
        return false;

    /* check zone order */
    for (i = 0; i < pse_mod_bprof->temp_mon_ranges; i++) {
        if (last_temp < pse_mod_bprof->temp_mon_range[i].temp_up_lim)
            return false;
        last_temp = pse_mod_bprof->temp_mon_range[i].temp_up_lim;
    }

    return true;
}

-- Sebastian

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