[PATCH v2] hwmon: (npcm750-pwm-fan): stop fan timer on device detach

[PATCH v2] hwmon: (npcm750-pwm-fan): stop fan timer on device detach

[Hongyan Xu]

When a fan tach channel is present, npcm7xx_pwm_fan_probe() starts
fan_timer. The timer callback polls tach state and rearms the timer, but
the driver has no remove callback or devm cleanup action to stop it. On
device detach, the devm-managed driver data and I/O mappings can be
released while the timer is still pending or running.

Register a devm cleanup action before starting the timer and shut the
timer down synchronously from that action.

This issue was found by a static analysis tool.

Fixes: f1fd4a4db777 ("hwmon: Add NPCM7xx PWM and Fan driver")
Cc: stable@vger.kernel.org
Signed-off-by: Hongyan Xu <getshell@seu.edu.cn>
---
v2:
- pass the fan timer directly to the cleanup action
- keep the timer expiration assignment in its original location

v1: https://lore.kernel.org/linux-hwmon/20260728075535.251-1-getshell@seu.edu.cn/

 drivers/hwmon/npcm750-pwm-fan.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/hwmon/npcm750-pwm-fan.c b/drivers/hwmon/npcm750-pwm-fan.c
index aea0b8659f5..6ff2a6bc06c 100644
--- a/drivers/hwmon/npcm750-pwm-fan.c
+++ b/drivers/hwmon/npcm750-pwm-fan.c
@@ -358,6 +358,11 @@ static void npcm7xx_fan_polling(struct timer_list *t)
 	add_timer(&data->fan_timer);
 }
 
+static void npcm7xx_fan_cleanup(void *timer)
+{
+	timer_shutdown_sync(timer);
+}
+
 static inline void npcm7xx_fan_compute(struct npcm7xx_pwm_fan_data *data,
 				       u8 fan, u8 cmp, u8 fan_id, u8 flag_int,
 				       u8 flag_mode, u8 flag_clear)
@@ -1020,6 +1025,12 @@ static int npcm7xx_pwm_fan_probe(struct platform_device *pdev)
 				msecs_to_jiffies(NPCM7XX_FAN_POLL_TIMER_200MS);
 			timer_setup(&data->fan_timer,
 				    npcm7xx_fan_polling, 0);
+			ret = devm_add_action_or_reset(dev,
+						       npcm7xx_fan_cleanup,
+						       &data->fan_timer);
+			if (ret)
+				return ret;
+
 			add_timer(&data->fan_timer);
 			break;
 		}
-- 
2.50.1.windows.1

Re: [PATCH v2] hwmon: (npcm750-pwm-fan): stop fan timer on device detach

[Guenter Roeck]

On Wed, Jul 29, 2026 at 06:01:16PM +0800, Hongyan Xu wrote:
> When a fan tach channel is present, npcm7xx_pwm_fan_probe() starts
> fan_timer. The timer callback polls tach state and rearms the timer, but
> the driver has no remove callback or devm cleanup action to stop it. On
> device detach, the devm-managed driver data and I/O mappings can be
> released while the timer is still pending or running.
> 
> Register a devm cleanup action before starting the timer and shut the
> timer down synchronously from that action.
> 
> This issue was found by a static analysis tool.
> 
> Fixes: f1fd4a4db777 ("hwmon: Add NPCM7xx PWM and Fan driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hongyan Xu <getshell@seu.edu.cn>

Applied.

Thanks,
Guenter