linux-kernel - [PATCH v2 2/5] hwmon: (sch5627) Disallow write access if virtual registers are locked

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Message-Id: <20230907052639.16491-3-W_Armin@gmx.de>
Date:   Thu,  7 Sep 2023 07:26:36 +0200
From:   Armin Wolf <W_Armin@....de>
To:     hdegoede@...hat.com
Cc:     jdelvare@...e.com, linux@...ck-us.net, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/5] hwmon: (sch5627) Disallow write access if virtual registers are locked

When the lock bit inside SCH5627_REG_CTRL is set, then the virtual
registers become read-only until the next power cycle.
Disallow write access to those registers in such a case.

Tested on a Fujitsu Esprimo P720.

Fixes: aa9f833dfc12 ("hwmon: (sch5627) Add pwmX_auto_channels_temp support")
Signed-off-by: Armin Wolf <W_Armin@....de>
---
 drivers/hwmon/sch5627.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/hwmon/sch5627.c b/drivers/hwmon/sch5627.c
index 0eefb8c0aef2..bf408e35e2c3 100644
--- a/drivers/hwmon/sch5627.c
+++ b/drivers/hwmon/sch5627.c
@@ -34,6 +34,7 @@
 #define SCH5627_REG_CTRL		0x40

 #define SCH5627_CTRL_START		BIT(0)
+#define SCH5627_CTRL_LOCK		BIT(1)
 #define SCH5627_CTRL_VBAT		BIT(4)

 #define SCH5627_NO_TEMPS		8
@@ -231,6 +232,14 @@ static int reg_to_rpm(u16 reg)
 static umode_t sch5627_is_visible(const void *drvdata, enum hwmon_sensor_types type, u32 attr,
 				  int channel)
 {
+	const struct sch5627_data *data = drvdata;
+
+	/* Once the lock bit is set, the virtual registers become read-only
+	 * until the next power cycle.
+	 */
+	if (data->control & SCH5627_CTRL_LOCK)
+		return 0444;
+
 	if (type == hwmon_pwm && attr == hwmon_pwm_auto_channels_temp)
 		return 0644;

--
2.39.2