Messages in this thread | | | From | "Tc, Jenny" <> | Subject | RE: [PATCH 3/4] power_supply: Introduce PSE compliant algorithm | Date | Fri, 11 Jul 2014 02:46:35 +0000 |
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> From: Sebastian Reichel [mailto:sre@kernel.org] > Sent: Tuesday, July 08, 2014 9:26 PM > To: Tc, Jenny > Cc: linux-kernel@vger.kernel.org; Dmitry Eremin-Solenikov; Pavel Machek; Stephen > Rothwell; Anton Vorontsov; David Woodhouse; David Cohen; Pallala, Ramakrishna > 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;
This is in a way good to have, OK to implement the same.
But KO with below suggestion. This doesn't guarantee safety. IMHO Safety is 1/0 - SAFE or NOT SAFE. No half safety.
To ensure complete safety, measures should be taken at the entry point- where data is read from external source. Since the algorithm gets the data from internal kernel component (power_supply_charger.c), it trust the data. Since the data is originated from battery identification driver, the safety should be ensured at that level.
> > /* 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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