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[2600:3c18:e002:2e11::c424]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-87d1e601b5dsm1685893b3a.61.2026.09.23.10.25.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 10:25:59 -0700 (PDT) From: Ridham Khurana To: Guenter Roeck Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, Shuah Khan , Jori Koolstra , Brigham Campbell , linux-kernel-mentees@lists.linux.dev, Ridham Khurana , stable@vger.kernel.org Subject: [PATCH] hwmon: (lm95245) Fix negative temperature conversion Date: Wed, 23 Sep 2026 17:25:48 +0000 Message-ID: <20260923172551.1593798-1-khurana.ridham222@gmail.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" temp_from_reg_signed() uses only the high byte when the sign bit is set and drops the fractional bits in the low byte. Writing -500 to temp2_offset stores 0xff80 (-0.5 degrees C) in the offset registers, but reading temp2_offset back returns -1000. Negative temp1_input and temp2_input values are rounded down to the next whole degree the same way. The chip reports -0.125 degrees C as 0xffe0, which the driver returns as -1000. Treat the register pair as a single 16-bit two's complement value. lm95241 had the same conversion fixed in commit 0c2a40e2fe4f ("hwmon: (lm95241) Fix negative temperature results"). Fixes: fffd80ccc1e6 ("hwmon: LM95245 driver") Cc: stable@vger.kernel.org Signed-off-by: Ridham Khurana --- Build-tested on arm64 with CONFIG_SENSORS_LM95245=3Dm, tested with i2c-stub= in QEMU. Not tested on hardware. drivers/hwmon/lm95245.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/hwmon/lm95245.c b/drivers/hwmon/lm95245.c index 11553391f54b..925574b8b0ca 100644 --- a/drivers/hwmon/lm95245.c +++ b/drivers/hwmon/lm95245.c @@ -96,9 +96,9 @@ static int temp_from_reg_unsigned(u8 val_h, u8 val_l) =20 static int temp_from_reg_signed(u8 val_h, u8 val_l) { - if (val_h & 0x80) - return (val_h - 0x100) * 1000; - return temp_from_reg_unsigned(val_h, val_l); + s16 val_hl =3D (val_h << 8) | val_l; + + return val_hl * 1000 / 256; } =20 static int lm95245_read_conversion_rate(struct lm95245_data *data) --=20 2.47.3