linux-kernel - [PATCH v2 2/2] power: supply: max17042_battery: Prevent int underflow in set_soc

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Message-Id: <20210914121806.1301131-2-sebastian.krzyszkowiak@puri.sm>
Date:   Tue, 14 Sep 2021 14:18:06 +0200
From:   Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
To:     Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Dirk Brandewie <dirk.brandewie@...il.com>, kernel@...i.sm,
        Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>,
        stable@...r.kernel.org
Subject: [PATCH v2 2/2] power: supply: max17042_battery: Prevent int underflow in set_soc_threshold

max17042_set_soc_threshold gets called with offset set to 1, which means
that minimum threshold value would underflow once SOC got down to 0,
causing invalid alerts from the gauge.

Fixes: e5f3872d2044 ("max17042: Add support for signalling change in SOC")
Cc: <stable@...r.kernel.org>
Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
---
v2: added commit description
---
 drivers/power/supply/max17042_battery.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/power/supply/max17042_battery.c b/drivers/power/supply/max17042_battery.c
index da78ffe6a3ec..189c1979bc7b 100644
--- a/drivers/power/supply/max17042_battery.c
+++ b/drivers/power/supply/max17042_battery.c
@@ -857,7 +857,8 @@ static void max17042_set_soc_threshold(struct max17042_chip *chip, u16 off)
 	regmap_read(map, MAX17042_RepSOC, &soc);
 	soc >>= 8;
 	soc_tr = (soc + off) << 8;
-	soc_tr |= (soc - off);
+	if (off < soc)
+		soc_tr |= soc - off;
 	regmap_write(map, MAX17042_SALRT_Th, soc_tr);
 }
 
-- 
2.33.0