Messages in this thread | | | Date | Thu, 30 Jul 2009 18:26:16 +0400 | From | Anton Vorontsov <> | Subject | Re: [PATCH] ds2760: fix integer overflow for time_to_empty_now |
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On Thu, Jul 30, 2009 at 04:12:59PM +0200, Daniel Mack wrote: > On Thu, Jul 30, 2009 at 06:00:41PM +0400, Anton Vorontsov wrote: > > On Fri, Jul 24, 2009 at 03:19:33PM +0200, Daniel Mack wrote: > > > On the device we're currently developing, battery sizes of ~2.8Ah and > > > current flow of ~600mA are typical. > > > > > > With that values, the life_sec computation overflows due to the > > > multiplication by 3600. > > > > > > Signed-off-by: Daniel Mack <daniel@caiaq.de> > > > Cc: Szabolcs Gyurko <szabolcs.gyurko@tlt.hu> > > > Cc: Matt Reimer <mreimer@vpop.net> > > > Cc: Anton Vorontsov <cbou@mail.ru> > > > > > > Signed-off-by: Daniel Mack <daniel@caiaq.de> > > > --- > > > drivers/power/ds2760_battery.c | 4 ++-- > > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/power/ds2760_battery.c b/drivers/power/ds2760_battery.c > > > index d545fee..5d30dc0 100644 > > > --- a/drivers/power/ds2760_battery.c > > > +++ b/drivers/power/ds2760_battery.c > > > @@ -212,8 +212,8 @@ static int ds2760_battery_read_status(struct ds2760_device_info *di) > > > di->rem_capacity = 100; > > > > > > if (di->current_uA) > > > - di->life_sec = -((di->accum_current_uAh - di->empty_uAh) * > > > - 3600L) / di->current_uA; > > > + di->life_sec = -((di->accum_current_uAh - di->empty_uAh) * 36L) > > > + / (di->current_uA / 100L); > > > > Hm... "(di->current_uA / 100L)" might result to 0, so you'll get > > div by zero. Removing the parenthesis will help. > > Hmm, no, then it gets the precedence wrong.
Ah.
> But checking for values >= > 100 of current_uA helps. Thanks for spotting this.
Yeah, that'll be fine indeed.
> Daniel > > > >From c60e23e2ba6667bec882338bfe3cb12304ee1ab6 Mon Sep 17 00:00:00 2001 > From: Daniel Mack <daniel@caiaq.de> > Date: Fri, 24 Jul 2009 15:08:11 +0200 > Subject: [PATCH] ds2760: fix integer overflow for time_to_empty_now > > On the device we're currently developing, battery sizes of ~2.8Ah and > current flow of ~600mA are typical. > > With that values, the life_sec computation overflows due to the > multiplication by 3600. > > Signed-off-by: Daniel Mack <daniel@caiaq.de> > Cc: Szabolcs Gyurko <szabolcs.gyurko@tlt.hu> > Cc: Matt Reimer <mreimer@vpop.net> > Cc: Anton Vorontsov <cbou@mail.ru> > > Signed-off-by: Daniel Mack <daniel@caiaq.de> > --- > drivers/power/ds2760_battery.c | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/power/ds2760_battery.c b/drivers/power/ds2760_battery.c > index d545fee..2ef29dd 100644 > --- a/drivers/power/ds2760_battery.c > +++ b/drivers/power/ds2760_battery.c > @@ -211,9 +211,9 @@ static int ds2760_battery_read_status(struct ds2760_device_info *di) > if (di->rem_capacity > 100) > di->rem_capacity = 100; > > - if (di->current_uA) > - di->life_sec = -((di->accum_current_uAh - di->empty_uAh) * > - 3600L) / di->current_uA; > + if (di->current_uA >= 100L) > + di->life_sec = -((di->accum_current_uAh - di->empty_uAh) * 36L) > + / (di->current_uA / 100L); > else > di->life_sec = 0; > > -- > 1.6.3.3 >
-- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2
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