linux-kernel - [PATCH 1/3] platform/x86: dell-ddv: Fix temperature calculation

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Message-Id: <20250305053009.378609-2-W_Armin@gmx.de>
Date: Wed,  5 Mar 2025 06:30:07 +0100
From: Armin Wolf <W_Armin@....de>
To: hdegoede@...hat.com,
	ilpo.jarvinen@...ux.intel.com,
	sre@...nel.org
Cc: platform-driver-x86@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] platform/x86: dell-ddv: Fix temperature calculation

On the Dell Inspiron 3505 the battery temperature is always
0.1 degrees larger than the temperature show inside the OEM
application.

Emulate this behaviour to avoid showing strange looking values
like 29.1 degrees.

Fixes: 0331b1b0ba653 ("platform/x86: dell-ddv: Fix temperature scaling")
Signed-off-by: Armin Wolf <W_Armin@....de>
---
 drivers/platform/x86/dell/dell-wmi-ddv.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-wmi-ddv.c b/drivers/platform/x86/dell/dell-wmi-ddv.c
index e75cd6e1efe6..ab5f7d3ab824 100644
--- a/drivers/platform/x86/dell/dell-wmi-ddv.c
+++ b/drivers/platform/x86/dell/dell-wmi-ddv.c
@@ -665,8 +665,10 @@ static ssize_t temp_show(struct device *dev, struct device_attribute *attr, char
 	if (ret < 0)
 		return ret;

-	/* Use 2731 instead of 2731.5 to avoid unnecessary rounding */
-	return sysfs_emit(buf, "%d\n", value - 2731);
+	/* Use 2732 instead of 2731.5 to avoid unnecessary rounding and to emulate
+	 * the behaviour of the OEM application which seems to round down the result.
+	 */
+	return sysfs_emit(buf, "%d\n", value - 2732);
 }

 static ssize_t eppid_show(struct device *dev, struct device_attribute *attr, char *buf)
--
2.39.5