[PATCH v2] iio: accel: kxsd9: fix runtime PM leaks and unchecked returns

[Biren Pandya <birenpandya@gmail.com>]

The kxsd9 driver uses pm_runtime_get_sync() without checking its return
value, which can lead to silent failures. It also relies on manual
pm_runtime_put_autosuspend() calls, which is prone to leaks.

Specifically, kxsd9_write_raw() contains a bug where returning -EINVAL
bypasses the pm_runtime_put_autosuspend() call, leaving the device
powered on.

Modernize the runtime PM handling to fix these issues:
- kxsd9_write_raw() & kxsd9_read_raw(): Use the scoped
  PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND() macro to safely automate
  cleanup on function return and remove all manual puts/error gotos.
- kxsd9_buffer_preenable(): Use pm_runtime_resume_and_get() to safely
  check for errors and handle usage-counter unwinding.
- kxsd9_common_remove(): Use pm_runtime_resume_and_get(), and reverse
  the disable ordering to call pm_runtime_disable() before powering down
  to prevent background RPM race conditions.

Fixes: 9a9a369d6178 ("iio: accel: kxsd9: Deploy system and runtime PM")
Signed-off-by: Biren Pandya <birenpandya@gmail.com>
---
Changes in v2:
- Changed subject to reflect broader PM modernization.
- In kxsd9_common_remove(), reversed the order to call pm_runtime_disable()
  before kxsd9_power_down() to prevent background RPM race conditions.
- Used standard error checking idiom in kxsd9_common_remove() (Andy).
- Clarified commit message regarding the exact write_raw() bug and added
  the Fixes tag (Jonathan).

 drivers/iio/accel/kxsd9.c | 47 ++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/drivers/iio/accel/kxsd9.c b/drivers/iio/accel/kxsd9.c
index 4717d80fc24a..7aa23ae64b7c 100644
--- a/drivers/iio/accel/kxsd9.c
+++ b/drivers/iio/accel/kxsd9.c
@@ -139,68 +139,63 @@ static int kxsd9_write_raw(struct iio_dev *indio_dev,
 			   int val2,
 			   long mask)
 {
-	int ret = -EINVAL;
 	struct kxsd9_state *st = iio_priv(indio_dev);
 
-	pm_runtime_get_sync(st->dev);
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->dev, pm);
+	if (PM_RUNTIME_ACQUIRE_ERR(&pm))
+		return PM_RUNTIME_ACQUIRE_ERR(&pm);
 
 	if (mask == IIO_CHAN_INFO_SCALE) {
 		/* Check no integer component */
 		if (val)
 			return -EINVAL;
-		ret = kxsd9_write_scale(indio_dev, val2);
+		return kxsd9_write_scale(indio_dev, val2);
 	}
 
-	pm_runtime_put_autosuspend(st->dev);
-
-	return ret;
+	return -EINVAL;
 }
 
 static int kxsd9_read_raw(struct iio_dev *indio_dev,
 			  struct iio_chan_spec const *chan,
 			  int *val, int *val2, long mask)
 {
-	int ret = -EINVAL;
 	struct kxsd9_state *st = iio_priv(indio_dev);
 	unsigned int regval;
 	__be16 raw_val;
 	u16 nval;
+	int ret;
 
-	pm_runtime_get_sync(st->dev);
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->dev, pm);
+	if (PM_RUNTIME_ACQUIRE_ERR(&pm))
+		return PM_RUNTIME_ACQUIRE_ERR(&pm);
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		ret = regmap_bulk_read(st->map, chan->address, &raw_val,
 				       sizeof(raw_val));
 		if (ret)
-			goto error_ret;
+			return ret;
 		nval = be16_to_cpu(raw_val);
 		/* Only 12 bits are valid */
 		nval >>= 4;
 		*val = nval;
-		ret = IIO_VAL_INT;
-		break;
+		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_OFFSET:
 		/* This has a bias of -2048 */
 		*val = KXSD9_ZERO_G_OFFSET;
-		ret = IIO_VAL_INT;
-		break;
+		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		ret = regmap_read(st->map,
 				  KXSD9_REG_CTRL_C,
 				  &regval);
 		if (ret < 0)
-			goto error_ret;
+			return ret;
 		*val = 0;
 		*val2 = kxsd9_micro_scales[regval & KXSD9_CTRL_C_FS_MASK];
-		ret = IIO_VAL_INT_PLUS_MICRO;
-		break;
+		return IIO_VAL_INT_PLUS_MICRO;
 	}
 
-error_ret:
-	pm_runtime_put_autosuspend(st->dev);
-
-	return ret;
+	return -EINVAL;
 };
 
 static irqreturn_t kxsd9_trigger_handler(int irq, void *p)
@@ -239,9 +234,7 @@ static int kxsd9_buffer_preenable(struct iio_dev *indio_dev)
 {
 	struct kxsd9_state *st = iio_priv(indio_dev);
 
-	pm_runtime_get_sync(st->dev);
-
-	return 0;
+	return pm_runtime_resume_and_get(st->dev);
 }
 
 static int kxsd9_buffer_postdisable(struct iio_dev *indio_dev)
@@ -476,13 +469,17 @@ void kxsd9_common_remove(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct kxsd9_state *st = iio_priv(indio_dev);
+	int ret;
 
 	iio_triggered_buffer_cleanup(indio_dev);
 	iio_device_unregister(indio_dev);
-	pm_runtime_get_sync(dev);
-	pm_runtime_put_noidle(dev);
+	ret = pm_runtime_resume_and_get(dev);
 	pm_runtime_disable(dev);
+	if (ret < 0)
+		return;
+
 	kxsd9_power_down(st);
+	pm_runtime_put_noidle(dev);
 }
 EXPORT_SYMBOL_NS(kxsd9_common_remove, "IIO_KXSD9");
 
-- 
2.50.1 (Apple Git-155)