linux-kernel - [PATCH AUTOSEL 4.14 1/5] hwmon: (f71882fg) Fix negative temperature

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Message-Id: <20220510154637.154283-1-sashal@kernel.org>
Date:   Tue, 10 May 2022 11:46:33 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>,
        Ji-Ze Hong <hpeter+linux_kernel@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Sasha Levin <sashal@...nel.org>, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 1/5] hwmon: (f71882fg) Fix negative temperature

From: "Ji-Ze Hong (Peter Hong)" <hpeter@...il.com>

[ Upstream commit 4aaaaf0f279836f06d3b9d0ffeec7a1e1a04ceef ]

All temperature of Fintek superio hwmonitor that using 1-byte reg will use
2's complement.

In show_temp()
	temp = data->temp[nr] * 1000;

When data->temp[nr] read as 255, it indicate -1C, but this code will report
255C to userspace. It'll be ok when change to:
	temp = ((s8)data->temp[nr]) * 1000;

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@...il.com>
Link: https://lore.kernel.org/r/20220418090706.6339-1-hpeter+linux_kernel@gmail.com
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hwmon/f71882fg.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/f71882fg.c b/drivers/hwmon/f71882fg.c
index ca54ce5c8e10..4010b61743f5 100644
--- a/drivers/hwmon/f71882fg.c
+++ b/drivers/hwmon/f71882fg.c
@@ -1590,8 +1590,9 @@ static ssize_t show_temp(struct device *dev, struct device_attribute *devattr,
 		temp *= 125;
 		if (sign)
 			temp -= 128000;
-	} else
-		temp = data->temp[nr] * 1000;
+	} else {
+		temp = ((s8)data->temp[nr]) * 1000;
+	}
 
 	return sprintf(buf, "%d\n", temp);
 }
-- 
2.35.1