[PATCH] iio: gyro: bmg160: reject duplicate event disable

[PATCH] iio: gyro: bmg160: reject duplicate event disable

[Jiale Yao]

The IIO core does not filter duplicate writes to the event enable
attribute. bmg160_write_event_config() already ignores repeated enable
requests, but a repeated disable request still calls
bmg160_set_power_state(data, false), dropping a runtime PM reference
that was not acquired for this request. This can underflow the runtime
PM usage count and trigger a "Runtime PM usage count underflow" warning.

Return early when the requested state already matches ev_enable_state.

Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 drivers/iio/gyro/bmg160_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/gyro/bmg160_core.c b/drivers/iio/gyro/bmg160_core.c
index d611341a0e2a..0b5621455216 100644
--- a/drivers/iio/gyro/bmg160_core.c
+++ b/drivers/iio/gyro/bmg160_core.c
@@ -761,7 +761,7 @@ static int bmg160_write_event_config(struct iio_dev *indio_dev,
 	struct bmg160_data *data = iio_priv(indio_dev);
 	int ret;
 
-	if (state && data->ev_enable_state)
+	if (state == data->ev_enable_state)
 		return 0;
 
 	mutex_lock(&data->mutex);
-- 
2.34.1

Re: [PATCH] iio: gyro: bmg160: reject duplicate event disable

[Andy Shevchenko]

On Fri, Sep 25, 2026 at 10:09:54PM +0800, Jiale Yao wrote:
> The IIO core does not filter duplicate writes to the event enable
> attribute.

Can it be done there once for all?

> bmg160_write_event_config() already ignores repeated enable
> requests, but a repeated disable request still calls
> bmg160_set_power_state(data, false), dropping a runtime PM reference
> that was not acquired for this request. This can underflow the runtime
> PM usage count and trigger a "Runtime PM usage count underflow" warning.
> 
> Return early when the requested state already matches ev_enable_state.

-- 
With Best Regards,
Andy Shevchenko

Re:Re: [PATCH] iio: gyro: bmg160: reject duplicate event disable

[jiale yao]

At 2026-09-25 22:18:05, "Andy Shevchenko" <andriy.shevchenko@intel.com> wrote:
>On Fri, Sep 25, 2026 at 10:09:54PM +0800, Jiale Yao wrote:
>> The IIO core does not filter duplicate writes to the event enable
>> attribute.
>
>Can it be done there once for all?

I don't think the core can safely do this generically, since it doesn't own
the per-event state and read_event_config() may reflect shared hardware state.

The runtime PM accounting is driver-specific, so handling duplicate writes in
the driver seems safer. gp2ap002 does the same in commit 579c049b4cb6,
refer https://lore.kernel.org/all/20260720193911.74919-2-nikhilgtr@gmail.com/

>
>> bmg160_write_event_config() already ignores repeated enable
>> requests, but a repeated disable request still calls
>> bmg160_set_power_state(data, false), dropping a runtime PM reference
>> that was not acquired for this request. This can underflow the runtime
>> PM usage count and trigger a "Runtime PM usage count underflow" warning.
>> 
>> Return early when the requested state already matches ev_enable_state.
>
>-- 
>With Best Regards,
>Andy Shevchenko
>