Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751522AbZG3ONG (ORCPT ); Thu, 30 Jul 2009 10:13:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751202AbZG3ONF (ORCPT ); Thu, 30 Jul 2009 10:13:05 -0400 Received: from buzzloop.caiaq.de ([212.112.241.133]:37667 "EHLO buzzloop.caiaq.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751133AbZG3ONE (ORCPT ); Thu, 30 Jul 2009 10:13:04 -0400 Date: Thu, 30 Jul 2009 16:12:59 +0200 From: Daniel Mack To: Anton Vorontsov Cc: linux-kernel@vger.kernel.org, Szabolcs Gyurko , Matt Reimer , Anton Vorontsov Subject: Re: [PATCH] ds2760: fix integer overflow for time_to_empty_now Message-ID: <20090730141259.GV19257@buzzloop.caiaq.de> References: <1248441573-32712-1-git-send-email-daniel@caiaq.de> <20090730140041.GA25759@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090730140041.GA25759@oksana.dev.rtsoft.ru> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3089 Lines: 86 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 > > Cc: Szabolcs Gyurko > > Cc: Matt Reimer > > Cc: Anton Vorontsov > > > > Signed-off-by: Daniel Mack > > --- > > 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. But checking for values >= 100 of current_uA helps. Thanks for spotting this. Daniel >From c60e23e2ba6667bec882338bfe3cb12304ee1ab6 Mon Sep 17 00:00:00 2001 From: Daniel Mack 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 Cc: Szabolcs Gyurko Cc: Matt Reimer Cc: Anton Vorontsov Signed-off-by: Daniel Mack --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/