[PATCH v3 2/2] iio: accel: kxsd9: fix runtime PM leaks and unchecked returns

[Biren Pandya <birenpandya@gmail.com>]

The kxsd9 driver previously used manual pm_runtime_get_sync() and
pm_runtime_put_autosuspend() calls in various return paths, which is
prone to memory leaks if a return path is missed. Specifically, in
kxsd9_write_raw(), if the user provides a non-zero integer component
for scale, the function previously returned -EINVAL directly, leaking
the runtime PM usage counter.

Switch to using the new scoped-based PM_RUNTIME_ACQUIRE_AUTOSUSPEND()
and PM_RUNTIME_ACQUIRE_ERR() macros to automatically handle dropping
the PM usage counter upon return. This simplifies the logic by allowing
early returns in error paths.

In remove(), use pm_runtime_resume_and_get() with an error check to
prevent unchecked return issues, and perform a best-effort power down.

Fixes: 9a9a369d6178 ("iio: accel: kxsd9: Deploy system and runtime PM")
Signed-off-by: Biren Pandya <birenpandya@gmail.com>
---
 drivers/iio/accel/kxsd9.c | 59 ++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 29 deletions(-)

diff --git a/drivers/iio/accel/kxsd9.c b/drivers/iio/accel/kxsd9.c
index 7569201ed3c75..a71b473cbfa03 100644
--- a/drivers/iio/accel/kxsd9.c
+++ b/drivers/iio/accel/kxsd9.c
@@ -139,68 +139,65 @@ 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);
+	int ret;
 
-	pm_runtime_get_sync(st->dev);
+	if (mask != IIO_CHAN_INFO_SCALE)
+		return -EINVAL;
 
-	if (mask == IIO_CHAN_INFO_SCALE) {
-		/* Check no integer component */
-		if (val)
-			return -EINVAL;
-		ret = kxsd9_write_scale(indio_dev, val2);
-	}
+	if (val)
+		return -EINVAL;
 
-	pm_runtime_put_autosuspend(st->dev);
+	PM_RUNTIME_ACQUIRE_AUTOSUSPEND(st->dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
 
-	return ret;
+	return kxsd9_write_scale(indio_dev, val2);
 }
 
 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_AUTOSUSPEND(st->dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
 
 	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 +236,7 @@ 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)
@@ -476,12 +471,18 @@ 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_device_unregister(indio_dev);
 	iio_triggered_buffer_cleanup(indio_dev);
-	pm_runtime_get_sync(dev);
-	pm_runtime_put_noidle(dev);
+
+	ret = pm_runtime_resume_and_get(dev);
+	if (ret < 0)
+		dev_warn(dev, "Failed to resume device (%d)\n", ret);
+
 	pm_runtime_disable(dev);
+	if (ret >= 0)
+		pm_runtime_put_noidle(dev);
 	kxsd9_power_down(st);
 }
 EXPORT_SYMBOL_NS(kxsd9_common_remove, "IIO_KXSD9");
-- 
2.50.1 (Apple Git-155)