[PATCH v2 1/3] iio: light: gp2ap002: Fix unbalanced runtime PM on repeated event writes

[Nikhil Gautam]

The IIO core does not filter duplicate writes to the event enable
attribute, so writing the same value twice invokes
write_event_config() twice. Enabling twice leaks a runtime PM
reference, preventing the device from ever suspending again;
disabling twice underflows the usage count and triggers a
"Runtime PM usage count underflow" warning.

Bail out early when the requested state matches the current state.
While at it, switch to pm_runtime_resume_and_get() so a failed
resume is propagated to userspace instead of silently marking the
event enabled.

Fixes: 97d642e23037c ("iio: light: Add a driver for Sharp GP2AP002x00F")
Signed-off-by: Nikhil Gautam <nikhilgtr@xxxxxxxxx>
---
 drivers/iio/light/gp2ap002.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/light/gp2ap002.c b/drivers/iio/light/gp2ap002.c
index 42859e5b1089..966459994995 100644
--- a/drivers/iio/light/gp2ap002.c
+++ b/drivers/iio/light/gp2ap002.c
@@ -343,6 +343,10 @@ static int gp2ap002_write_event_config(struct iio_dev *indio_dev,
 				       bool state)
 {
 	struct gp2ap002 *gp2ap002 = iio_priv(indio_dev);
+	int ret;
+
+	if (state == gp2ap002->enabled)
+		return 0;
 
 	if (state) {
 		/*
@@ -350,14 +354,15 @@ static int gp2ap002_write_event_config(struct iio_dev *indio_dev,
 		 * already) and reintialize the sensor by using runtime_pm
 		 * callbacks.
 		 */
-		pm_runtime_get_sync(gp2ap002->dev);
-		gp2ap002->enabled = true;
+
+		ret = pm_runtime_resume_and_get(gp2ap002->dev);
+		if (ret)
+			return ret;
 	} else {
-		pm_runtime_mark_last_busy(gp2ap002->dev);
 		pm_runtime_put_autosuspend(gp2ap002->dev);
-		gp2ap002->enabled = false;
 	}
 
+	gp2ap002->enabled = state;
 	return 0;
 }
 
-- 
2.39.5