[PATCH v2 02/27] iio: chemical: scd30: Use guard(mutex) to allow early returns

[Jonathan Cameron <jic23@xxxxxxxxxx>]

From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

Auto cleanup based release of the lock allows for simpler code flow in a
few functions with large multiplexing style switch statements and no
common operations following the switch.

Suggested-by: David Lechner <dlechner@xxxxxxxxxxxx>
Cc: Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
Reviewed-by: David Lechner <dlechner@xxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>

---
v2: Fix include ordering (David)
---
 drivers/iio/chemical/scd30_core.c | 63 ++++++++++++++-----------------
 include/linux/iio/iio.h           |  1 +
 2 files changed, 29 insertions(+), 35 deletions(-)

diff --git a/drivers/iio/chemical/scd30_core.c b/drivers/iio/chemical/scd30_core.c
index d613c54cb28d..23ba46f7ca32 100644
--- a/drivers/iio/chemical/scd30_core.c
+++ b/drivers/iio/chemical/scd30_core.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@xxxxxxxxxxx>
  */
 #include <linux/bits.h>
+#include <linux/cleanup.h>
 #include <linux/completion.h>
 #include <linux/delay.h>
 #include <linux/device.h>
@@ -198,112 +199,104 @@ static int scd30_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const
 			  int *val, int *val2, long mask)
 {
 	struct scd30_state *state = iio_priv(indio_dev);
-	int ret = -EINVAL;
+	int ret;
 	u16 tmp;
 
-	mutex_lock(&state->lock);
+	guard(mutex)(&state->lock);
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 	case IIO_CHAN_INFO_PROCESSED:
 		if (chan->output) {
 			*val = state->pressure_comp;
-			ret = IIO_VAL_INT;
-			break;
+			return IIO_VAL_INT;
 		}
 
 		ret = iio_device_claim_direct_mode(indio_dev);
 		if (ret)
-			break;
+			return ret;
 
 		ret = scd30_read(state);
 		if (ret) {
 			iio_device_release_direct_mode(indio_dev);
-			break;
+			return ret;
 		}
 
 		*val = state->meas[chan->address];
 		iio_device_release_direct_mode(indio_dev);
-		ret = IIO_VAL_INT;
-		break;
+		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		*val = 0;
 		*val2 = 1;
-		ret = IIO_VAL_INT_PLUS_MICRO;
-		break;
+		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		ret = scd30_command_read(state, CMD_MEAS_INTERVAL, &tmp);
 		if (ret)
-			break;
+			return ret;
 
 		*val = 0;
 		*val2 = 1000000000 / tmp;
-		ret = IIO_VAL_INT_PLUS_NANO;
-		break;
+		return IIO_VAL_INT_PLUS_NANO;
 	case IIO_CHAN_INFO_CALIBBIAS:
 		ret = scd30_command_read(state, CMD_TEMP_OFFSET, &tmp);
 		if (ret)
-			break;
+			return ret;
 
 		*val = tmp;
-		ret = IIO_VAL_INT;
-		break;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
 	}
-	mutex_unlock(&state->lock);
-
-	return ret;
 }
 
 static int scd30_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
 			   int val, int val2, long mask)
 {
 	struct scd30_state *state = iio_priv(indio_dev);
-	int ret = -EINVAL;
+	int ret;
 
-	mutex_lock(&state->lock);
+	guard(mutex)(&state->lock);
 	switch (mask) {
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		if (val)
-			break;
+			return -EINVAL;
 
 		val = 1000000000 / val2;
 		if (val < SCD30_MEAS_INTERVAL_MIN_S || val > SCD30_MEAS_INTERVAL_MAX_S)
-			break;
+			return -EINVAL;
 
 		ret = scd30_command_write(state, CMD_MEAS_INTERVAL, val);
 		if (ret)
-			break;
+			return ret;
 
 		state->meas_interval = val;
-		break;
+		return 0;
 	case IIO_CHAN_INFO_RAW:
 		switch (chan->type) {
 		case IIO_PRESSURE:
 			if (val < SCD30_PRESSURE_COMP_MIN_MBAR ||
 			    val > SCD30_PRESSURE_COMP_MAX_MBAR)
-				break;
+				return -EINVAL;
 
 			ret = scd30_command_write(state, CMD_START_MEAS, val);
 			if (ret)
-				break;
+				return ret;
 
 			state->pressure_comp = val;
-			break;
+			return 0;
 		default:
-			break;
+			return -EINVAL;
 		}
-		break;
 	case IIO_CHAN_INFO_CALIBBIAS:
 		if (val < 0 || val > SCD30_TEMP_OFFSET_MAX)
-			break;
+			return -EINVAL;
 		/*
 		 * Manufacturer does not explicitly specify min/max sensible
 		 * values hence check is omitted for simplicity.
 		 */
-		ret = scd30_command_write(state, CMD_TEMP_OFFSET / 10, val);
+		return scd30_command_write(state, CMD_TEMP_OFFSET / 10, val);
+	default:
+		return -EINVAL;
 	}
-	mutex_unlock(&state->lock);
-
-	return ret;
 }
 
 static int scd30_write_raw_get_fmt(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index fe33835b19cf..5ed03e36178f 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -10,6 +10,7 @@
 #include <linux/device.h>
 #include <linux/cdev.h>
 #include <linux/cleanup.h>
+#include <linux/compiler_types.h>
 #include <linux/slab.h>
 #include <linux/iio/types.h>
 /* IIO TODO LIST */
-- 
2.48.1