[PATCH] hwmon: (gpio-fan) take fan_data->lock in gpio_fan_shutdown()

[Cong Nguyen <congnt264@gmail.com>]

set_fan_speed() writes the control GPIOs one bit at a time. Every
other caller locks around it; gpio_fan_shutdown() doesn't. If it races
a locked caller, the GPIO writes can interleave and leave the fan at a
speed neither caller asked for.

Fixes: b95579cd8795 ("hwmon: (gpio-fan) Add a shutdown handler to poweroff the fans")
Reported-by: Sashiko AI review <sashiko-bot@kernel.org>
Link: https://lore.kernel.org/r/20260830152150.27F5F1F000E9@smtp.kernel.org
Assisted-by: Claude:claude-opus-4
Signed-off-by: Cong Nguyen <congnt264@gmail.com>
---
 drivers/hwmon/gpio-fan.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c
index 084828e1e281..10c91bc33b02 100644
--- a/drivers/hwmon/gpio-fan.c
+++ b/drivers/hwmon/gpio-fan.c
@@ -606,8 +606,11 @@ static void gpio_fan_shutdown(struct platform_device *pdev)
 {
 	struct gpio_fan_data *fan_data = platform_get_drvdata(pdev);
 
-	if (fan_data->gpios)
+	if (fan_data->gpios) {
+		mutex_lock(&fan_data->lock);
 		set_fan_speed(fan_data, 0);
+		mutex_unlock(&fan_data->lock);
+	}
 }
 
 static int gpio_fan_runtime_suspend(struct device *dev)
-- 
2.25.1