[PATCH v8] iio: magnetometer: bmc150_magn: use automated cleanup for mutex

[Neel Bullywon <neelb2403@gmail.com>]

Use guard() and scoped_guard() to replace manual mutex lock/unlock
calls. This simplifies error handling and ensures RAII-style cleanup.

guard() is used in read_raw, write_raw, trig_reen, and
trigger_set_state. Case blocks using guard() in read_raw and write_raw
are wrapped in braces at the case label level to ensure clear scope for
the cleanup guards.

A bmc150_magn_set_power_mode_locked() helper is added to deduplicate
the lock-call-unlock pattern used by remove, runtime_suspend, suspend,
and resume.

The trigger_handler function is left unchanged as mixing guard() with
goto error paths can be fragile.

Signed-off-by: Neel Bullywon <neelb2403@gmail.com>
---
I don't have BMC150 hardware, so I went with Andy's _locked() helper
approach rather than moving the guard into bmc150_magn_set_power_mode()
itself, which would touch the runtime PM locking Jonathan flagged as
suspicious. The deeper runtime PM cleanup can be done separately by
someone who can test it.

v8:
  - Add bmc150_magn_set_power_mode_locked() helper to deduplicate the
    lock-call-unlock pattern in remove, runtime_suspend, suspend, and
    resume (Andy Shevchenko)
v7:
  - Split into separate patches (Jonathan Cameron)
v6:
  - Remove scoped_guard() from runtime_suspend and use guard() in
    suspend/resume (Jonathan Cameron)
v5:
  - Use scoped_guard() instead of guard() in remove and
    runtime_suspend (Andy Shevchenko)

 drivers/iio/magnetometer/bmc150_magn.c | 112 ++++++++++---------------
 1 file changed, 44 insertions(+), 68 deletions(-)

diff --git a/drivers/iio/magnetometer/bmc150_magn.c b/drivers/iio/magnetometer/bmc150_magn.c
index 6a73f6e2f1f0..a4e2209f6ed4 100644
--- a/drivers/iio/magnetometer/bmc150_magn.c
+++ b/drivers/iio/magnetometer/bmc150_magn.c
@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
+#include <linux/cleanup.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/pm.h>
@@ -255,6 +256,13 @@ static int bmc150_magn_set_power_mode(struct bmc150_magn_data *data,
 	return -EINVAL;
 }
 
+static int bmc150_magn_set_power_mode_locked(struct bmc150_magn_data *data,
+					     enum bmc150_magn_power_modes mode)
+{
+	guard(mutex)(&data->mutex);
+	return bmc150_magn_set_power_mode(data, mode, true);
+}
+
 static int bmc150_magn_set_power_state(struct bmc150_magn_data *data, bool on)
 {
 	int ret = 0;
@@ -453,33 +461,29 @@ static int bmc150_magn_read_raw(struct iio_dev *indio_dev,
 	s32 values[AXIS_XYZ_MAX];
 
 	switch (mask) {
-	case IIO_CHAN_INFO_RAW:
+	case IIO_CHAN_INFO_RAW: {
 		if (iio_buffer_enabled(indio_dev))
 			return -EBUSY;
-		mutex_lock(&data->mutex);
+
+		guard(mutex)(&data->mutex);
 
 		ret = bmc150_magn_set_power_state(data, true);
-		if (ret < 0) {
-			mutex_unlock(&data->mutex);
+		if (ret < 0)
 			return ret;
-		}
 
 		ret = bmc150_magn_read_xyz(data, values);
 		if (ret < 0) {
 			bmc150_magn_set_power_state(data, false);
-			mutex_unlock(&data->mutex);
 			return ret;
 		}
 		*val = values[chan->scan_index];
 
 		ret = bmc150_magn_set_power_state(data, false);
-		if (ret < 0) {
-			mutex_unlock(&data->mutex);
+		if (ret < 0)
 			return ret;
-		}
 
-		mutex_unlock(&data->mutex);
 		return IIO_VAL_INT;
+	}
 	case IIO_CHAN_INFO_SCALE:
 		/*
 		 * The API/driver performs an off-chip temperature
@@ -527,48 +531,39 @@ static int bmc150_magn_write_raw(struct iio_dev *indio_dev,
 	int ret;
 
 	switch (mask) {
-	case IIO_CHAN_INFO_SAMP_FREQ:
+	case IIO_CHAN_INFO_SAMP_FREQ: {
 		if (val > data->max_odr)
 			return -EINVAL;
-		mutex_lock(&data->mutex);
-		ret = bmc150_magn_set_odr(data, val);
-		mutex_unlock(&data->mutex);
-		return ret;
+		guard(mutex)(&data->mutex);
+		return bmc150_magn_set_odr(data, val);
+	}
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
 		switch (chan->channel2) {
 		case IIO_MOD_X:
-		case IIO_MOD_Y:
+		case IIO_MOD_Y: {
 			if (val < 1 || val > 511)
 				return -EINVAL;
-			mutex_lock(&data->mutex);
+			guard(mutex)(&data->mutex);
 			ret = bmc150_magn_set_max_odr(data, val, 0, 0);
-			if (ret < 0) {
-				mutex_unlock(&data->mutex);
+			if (ret < 0)
 				return ret;
-			}
-			ret = regmap_update_bits(data->regmap,
+			return regmap_update_bits(data->regmap,
 						 BMC150_MAGN_REG_REP_XY,
 						 BMC150_MAGN_REG_REP_DATAMASK,
-						 BMC150_MAGN_REPXY_TO_REGVAL
-						 (val));
-			mutex_unlock(&data->mutex);
-			return ret;
-		case IIO_MOD_Z:
+						 BMC150_MAGN_REPXY_TO_REGVAL(val));
+		}
+		case IIO_MOD_Z: {
 			if (val < 1 || val > 256)
 				return -EINVAL;
-			mutex_lock(&data->mutex);
+			guard(mutex)(&data->mutex);
 			ret = bmc150_magn_set_max_odr(data, 0, val, 0);
-			if (ret < 0) {
-				mutex_unlock(&data->mutex);
+			if (ret < 0)
 				return ret;
-			}
-			ret = regmap_update_bits(data->regmap,
+			return regmap_update_bits(data->regmap,
 						 BMC150_MAGN_REG_REP_Z,
 						 BMC150_MAGN_REG_REP_DATAMASK,
-						 BMC150_MAGN_REPZ_TO_REGVAL
-						 (val));
-			mutex_unlock(&data->mutex);
-			return ret;
+						 BMC150_MAGN_REPZ_TO_REGVAL(val));
+		}
 		default:
 			return -EINVAL;
 		}
@@ -782,9 +777,8 @@ static void bmc150_magn_trig_reen(struct iio_trigger *trig)
 	if (!data->dready_trigger_on)
 		return;
 
-	mutex_lock(&data->mutex);
+	guard(mutex)(&data->mutex);
 	ret = bmc150_magn_reset_intr(data);
-	mutex_unlock(&data->mutex);
 	if (ret)
 		dev_err(data->dev, "Failed to reset interrupt\n");
 }
@@ -794,32 +788,28 @@ static int bmc150_magn_data_rdy_trigger_set_state(struct iio_trigger *trig,
 {
 	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
 	struct bmc150_magn_data *data = iio_priv(indio_dev);
-	int ret = 0;
+	int ret;
+
+	guard(mutex)(&data->mutex);
 
-	mutex_lock(&data->mutex);
 	if (state == data->dready_trigger_on)
-		goto err_unlock;
+		return 0;
 
 	ret = regmap_update_bits(data->regmap, BMC150_MAGN_REG_INT_DRDY,
 				 BMC150_MAGN_MASK_DRDY_EN,
 				 state << BMC150_MAGN_SHIFT_DRDY_EN);
 	if (ret < 0)
-		goto err_unlock;
+		return ret;
 
 	data->dready_trigger_on = state;
 
 	if (state) {
 		ret = bmc150_magn_reset_intr(data);
 		if (ret < 0)
-			goto err_unlock;
+			return ret;
 	}
-	mutex_unlock(&data->mutex);
 
 	return 0;
-
-err_unlock:
-	mutex_unlock(&data->mutex);
-	return ret;
 }
 
 static const struct iio_trigger_ops bmc150_magn_trigger_ops = {
@@ -980,9 +970,7 @@ void bmc150_magn_remove(struct device *dev)
 	if (data->dready_trig)
 		iio_trigger_unregister(data->dready_trig);
 
-	mutex_lock(&data->mutex);
-	bmc150_magn_set_power_mode(data, BMC150_MAGN_POWER_MODE_SUSPEND, true);
-	mutex_unlock(&data->mutex);
+	bmc150_magn_set_power_mode_locked(data, BMC150_MAGN_POWER_MODE_SUSPEND);
 
 	regulator_bulk_disable(ARRAY_SIZE(data->regulators), data->regulators);
 }
@@ -995,10 +983,8 @@ static int bmc150_magn_runtime_suspend(struct device *dev)
 	struct bmc150_magn_data *data = iio_priv(indio_dev);
 	int ret;
 
-	mutex_lock(&data->mutex);
-	ret = bmc150_magn_set_power_mode(data, BMC150_MAGN_POWER_MODE_SLEEP,
-					 true);
-	mutex_unlock(&data->mutex);
+	ret = bmc150_magn_set_power_mode_locked(data,
+						BMC150_MAGN_POWER_MODE_SLEEP);
 	if (ret < 0) {
 		dev_err(dev, "powering off device failed\n");
 		return ret;
@@ -1024,28 +1010,18 @@ static int bmc150_magn_suspend(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct bmc150_magn_data *data = iio_priv(indio_dev);
-	int ret;
 
-	mutex_lock(&data->mutex);
-	ret = bmc150_magn_set_power_mode(data, BMC150_MAGN_POWER_MODE_SLEEP,
-					 true);
-	mutex_unlock(&data->mutex);
-
-	return ret;
+	return bmc150_magn_set_power_mode_locked(data,
+						 BMC150_MAGN_POWER_MODE_SLEEP);
 }
 
 static int bmc150_magn_resume(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct bmc150_magn_data *data = iio_priv(indio_dev);
-	int ret;
 
-	mutex_lock(&data->mutex);
-	ret = bmc150_magn_set_power_mode(data, BMC150_MAGN_POWER_MODE_NORMAL,
-					 true);
-	mutex_unlock(&data->mutex);
-
-	return ret;
+	return bmc150_magn_set_power_mode_locked(data,
+						 BMC150_MAGN_POWER_MODE_NORMAL);
 }
 #endif
 
-- 
2.44.0