From acc52bd431e2d8698fae8d82a74ac45d79b62e0a Mon Sep 17 00:00:00 2001 From: Cong Nguyen Date: Mon, 10 Aug 2026 11:28:39 +0700 Subject: [PATCH] hwmon: (max6621) fix negative temperature offset and crit readings max6621_read() reads the CONFIG2 offset and the critical alert threshold registers into a u32 and scales them without sign extension: /* offset */ *val = (regval >> MAX6621_REG_TEMP_SHIFT) * 1000L; /* crit */ *val = regval * 1000L; Both attributes are writable and their write paths clamp to a negative minimum and encode negative values, so a value written as negative is read back as a large positive number. For example, writing a -10 degrees C offset stores max6621_temp_mc2reg(-10000) = (-10 << 6) = 0xfd80; the read then computes 0xfd80 >> 6 = 1014 -> 1014000 instead of -10000. Cast the register value to s16 before scaling so the read preserves the sign the write path encodes. The temperature input path already uses an s8 intermediate and is left unchanged. Fixes: 92b64580f14b ("hwmon: (max6621) Add support for Maxim MAX6621 temperature sensor") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4 Signed-off-by: Cong Nguyen Link: https://lore.kernel.org/r/ad0baddbd6163cf73545c8e9273258136718585c.1786334038.git.congnt264@gmail.com Signed-off-by: Guenter Roeck --- drivers/hwmon/max6621.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/max6621.c b/drivers/hwmon/max6621.c index 16a3a61d2532..1a644d787143 100644 --- a/drivers/hwmon/max6621.c +++ b/drivers/hwmon/max6621.c @@ -239,7 +239,7 @@ max6621_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, if (ret) return ret; - *val = (regval >> MAX6621_REG_TEMP_SHIFT) * + *val = ((s16)regval >> MAX6621_REG_TEMP_SHIFT) * 1000L; break; @@ -254,7 +254,7 @@ max6621_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, if (ret) return ret; - *val = regval * 1000L; + *val = (s16)regval * 1000L; break; case hwmon_temp_crit_alarm: