linux-kernel - [PATCH] ds2760: fix integer overflow for time_to_empty

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Message-Id: <1248441573-32712-1-git-send-email-daniel@caiaq.de>
Date:	Fri, 24 Jul 2009 15:19:33 +0200
From:	Daniel Mack <daniel@...aq.de>
To:	linux-kernel@...r.kernel.org
Cc:	Daniel Mack <daniel@...aq.de>,
	Szabolcs Gyurko <szabolcs.gyurko@....hu>,
	Matt Reimer <mreimer@...p.net>, Anton Vorontsov <cbou@...l.ru>
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@...aq.de>
Cc: Szabolcs Gyurko <szabolcs.gyurko@....hu>
Cc: Matt Reimer <mreimer@...p.net>
Cc: Anton Vorontsov <cbou@...l.ru>

Signed-off-by: Daniel Mack <daniel@...aq.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);
 	else
 		di->life_sec = 0;
 
-- 
1.6.3.1

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