[PATCH] ds2760_battery.c: fix division by zero

Daniel Mack
2009-03-09T15:53:47Z

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The 'battery remaining capacity' calculation in
drivers/power/ds2760_battery.c lacks a parameter check to a division
operation which causes the kernel to oops on my board.

[ 21.233750] Division by zero in kernel.
[ 21.237646] [<c002955c>] (__div0+0x0/0x20) from [<c012561c>] (Ldiv0+0x8/0x10)
[ 21.244816] [<c01bef34>] (ds2760_battery_read_status+0x0/0x2a4) from [<c01bf3a4>] (ds2760_battery_get_property+0x30/0xdc)
[ 21.255803] r8:c03a22c0 r7:c7886100 r6:00000009 r5:c782fe7c r4:c7886084
[ 21.262518] [<c01bf374>] (ds2760_battery_get_property+0x0/0xdc) from [<c01bde98>] (power_supply_show_property+0x48/0x114)
[ 21.273480] r6:c7996000 r5:00000009 r4:00000000
[ 21.278111] [<c01bde50>] (power_supply_show_property+0x0/0x114) from [<c01be158>] (power_supply_uevent+0x188/0x280)
[ 21.288537] r8:00000001 r7:c7886100 r6:c7996000 r5:000000b4 r4:00000000
[ 21.295222] [<c01bdfd0>] (power_supply_uevent+0x0/0x280) from [<c015c664>] (dev_uevent+0xd4/0x10c)
[ 21.304199] [<c015c590>] (dev_uevent+0x0/0x10c) from [<c0128440>] (kobject_uevent_env+0x180/0x390)
[ 21.313170] r5:00000000 r4:c78860ac
[ 21.316725] [<c01282c0>] (kobject_uevent_env+0x0/0x390) from [<c0128664>] (kobject_uevent+0x14/0x18)
[ 21.325850] [<c0128650>] (kobject_uevent+0x0/0x18) from [<c01bdc34>] (power_supply_changed_work+0x5c/0x70)
[ 21.335506] [<c01bdbd8>] (power_supply_changed_work+0x0/0x70) from [<c004d290>] (run_workqueue+0xbc/0x144)
[ 21.345167] r4:c7812040
[ 21.347716] [<c004d1d4>] (run_workqueue+0x0/0x144) from [<c004d94c>] (worker_thread+0xa8/0xbc)
[ 21.356296] r7:c7812040 r6:c7820b00 r5:c782ffa4 r4:c7812048
[ 21.361957] [<c004d8a4>] (worker_thread+0x0/0xbc) from [<c0051008>] (kthread+0x5c/0x94)
[ 21.369971] r7:00000000 r6:c004d8a4 r5:c7812040 r4:c782e000
[ 21.375612] [<c0050fac>] (kthread+0x0/0x94) from [<c00403d0>] (do_exit+0x0/0x688)

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>
Cc: David Woodhouse <dwmw2@infradead.org>
---
drivers/power/ds2760_battery.c | 11 +++++++----
1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/power/ds2760_battery.c b/drivers/power/ds2760_battery.c
index 1d76892..a52d4a1 100644
--- a/drivers/power/ds2760_battery.c
+++ b/drivers/power/ds2760_battery.c
@@ -180,10 +180,13 @@ static int ds2760_battery_read_status(struct ds2760_device_info *di)
di->empty_uAh = battery_interpolate(scale, di->temp_C / 10);
di->empty_uAh *= 1000; /* convert to µAh */

- /* From Maxim Application Note 131: remaining capacity =
- * ((ICA - Empty Value) / (Full Value - Empty Value)) x 100% */
- di->rem_capacity = ((di->accum_current_uAh - di->empty_uAh) * 100L) /
- (di->full_active_uAh - di->empty_uAh);
+ if (di->full_active_uAh == di->empty_uAh)
+ di->rem_capacity = 0;
+ else
+ /* From Maxim Application Note 131: remaining capacity =
+ * ((ICA - Empty Value) / (Full Value - Empty Value)) x 100% */
+ di->rem_capacity = ((di->accum_current_uAh - di->empty_uAh) * 100L) /
+ (di->full_active_uAh - di->empty_uAh);

if (di->rem_capacity < 0)
di->rem_capacity = 0;
--
1.6.1.3