[PATCH v2 2/2] iio: pressure: bmp280: Use char instead of s32 for data buffer

[Vasileios Amoiridis <vassilisamir@gmail.com>]

As it was reported and discussed here [1], storing the sensor data in an
endian aware s32 buffer is not optimal. Advertising the timestamp as an
addition of 2 s32 variables which is also implied is again not the best
practice. For that reason, change the s32 sensor_data buffer to a char
buffer with an extra value for the timestamp (as it is common practice).

[1]: https://lore.kernel.org/linux-iio/73d13cc0-afb9-4306-b498-5d821728c3ba@stanley.mountain/

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
 drivers/iio/pressure/bmp280-core.c | 78 ++++++++++++++++++------------
 drivers/iio/pressure/bmp280.h      |  5 +-
 2 files changed, 51 insertions(+), 32 deletions(-)

diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
index 472a6696303b..2c62490a40c6 100644
--- a/drivers/iio/pressure/bmp280-core.c
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -1023,9 +1023,9 @@ static irqreturn_t bmp280_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct bmp280_data *data = iio_priv(indio_dev);
-	u32 adc_temp, adc_press;
-	s32 t_fine;
-	int ret;
+	u32 adc_temp, adc_press, comp_press;
+	s32 t_fine, comp_temp;
+	int ret, offset;
 
 	guard(mutex)(&data->lock);
 
@@ -1044,7 +1044,7 @@ static irqreturn_t bmp280_trigger_handler(int irq, void *p)
 		goto out;
 	}
 
-	data->sensor_data[1] = bmp280_compensate_temp(data, adc_temp);
+	comp_temp = bmp280_compensate_temp(data, adc_temp);
 
 	/* Pressure calculations */
 	adc_press = FIELD_GET(BMP280_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[0]));
@@ -1054,10 +1054,13 @@ static irqreturn_t bmp280_trigger_handler(int irq, void *p)
 	}
 
 	t_fine = bmp280_calc_t_fine(data, adc_temp);
+	comp_press = bmp280_compensate_press(data, adc_press, t_fine);
 
-	data->sensor_data[0] = bmp280_compensate_press(data, adc_press, t_fine);
+	memcpy(&data->buffer.buf[offset], &comp_press, sizeof(s32));
+	offset += sizeof(s32);
+	memcpy(&data->buffer.buf[offset], &comp_temp, sizeof(s32));
 
-	iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
 					   iio_get_time_ns(indio_dev));
 
 out:
@@ -1138,9 +1141,9 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct bmp280_data *data = iio_priv(indio_dev);
-	u32 adc_temp, adc_press, adc_humidity;
-	s32 t_fine;
-	int ret;
+	u32 adc_temp, adc_press, adc_humidity, comp_press, comp_humidity;
+	s32 t_fine, comp_temp;
+	int ret, offset;
 
 	guard(mutex)(&data->lock);
 
@@ -1159,7 +1162,7 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
 		goto out;
 	}
 
-	data->sensor_data[1] = bmp280_compensate_temp(data, adc_temp);
+	comp_temp = bmp280_compensate_temp(data, adc_temp);
 
 	/* Pressure calculations */
 	adc_press = FIELD_GET(BMP280_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[0]));
@@ -1169,8 +1172,7 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
 	}
 
 	t_fine = bmp280_calc_t_fine(data, adc_temp);
-
-	data->sensor_data[0] = bmp280_compensate_press(data, adc_press, t_fine);
+	comp_press = bmp280_compensate_press(data, adc_press, t_fine);
 
 	/* Humidity calculations */
 	adc_humidity = get_unaligned_be16(&data->buf[6]);
@@ -1179,9 +1181,16 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
 		dev_err(data->dev, "reading humidity skipped\n");
 		goto out;
 	}
-	data->sensor_data[2] = bme280_compensate_humidity(data, adc_humidity, t_fine);
 
-	iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
+	comp_humidity = bme280_compensate_humidity(data, adc_humidity, t_fine);
+
+	memcpy(&data->buffer.buf[offset], &comp_press, sizeof(s32));
+	offset += sizeof(s32);
+	memcpy(&data->buffer.buf[offset], &comp_temp, sizeof(s32));
+	offset += sizeof(s32);
+	memcpy(&data->buffer.buf[offset], &comp_humidity, sizeof(s32));
+
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
 					   iio_get_time_ns(indio_dev));
 
 out:
@@ -1618,9 +1627,9 @@ static irqreturn_t bmp380_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct bmp280_data *data = iio_priv(indio_dev);
-	u32 adc_temp, adc_press;
-	s32 t_fine;
-	int ret;
+	u32 adc_temp, adc_press, comp_press;
+	s32 t_fine, comp_temp;
+	int ret, offset;
 
 	guard(mutex)(&data->lock);
 
@@ -1639,7 +1648,7 @@ static irqreturn_t bmp380_trigger_handler(int irq, void *p)
 		goto out;
 	}
 
-	data->sensor_data[1] = bmp380_compensate_temp(data, adc_temp);
+	comp_temp = bmp380_compensate_temp(data, adc_temp);
 
 	/* Pressure calculations */
 	adc_press = get_unaligned_le24(&data->buf[0]);
@@ -1649,10 +1658,13 @@ static irqreturn_t bmp380_trigger_handler(int irq, void *p)
 	}
 
 	t_fine = bmp380_calc_t_fine(data, adc_temp);
+	comp_press = bmp380_compensate_press(data, adc_press, t_fine);
 
-	data->sensor_data[0] = bmp380_compensate_press(data, adc_press, t_fine);
+	memcpy(&data->buffer.buf[offset], &comp_press, sizeof(s32));
+	offset += sizeof(s32);
+	memcpy(&data->buffer.buf[offset], &comp_temp, sizeof(s32));
 
-	iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
 					   iio_get_time_ns(indio_dev));
 
 out:
@@ -2199,7 +2211,7 @@ static irqreturn_t bmp580_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct bmp280_data *data = iio_priv(indio_dev);
-	int ret;
+	int ret, offset;
 
 	guard(mutex)(&data->lock);
 
@@ -2211,13 +2223,16 @@ static irqreturn_t bmp580_trigger_handler(int irq, void *p)
 		goto out;
 	}
 
+	/* Pressure calculations */
+	memcpy(&data->buffer.buf[offset], &data->buf[3], 3);
+
+	offset += sizeof(s32);
+
 	/* Temperature calculations */
-	memcpy(&data->sensor_data[1], &data->buf[0], 3);
+	memcpy(&data->buffer.buf[offset], &data->buf[0], 3);
 
-	/* Pressure calculations */
-	memcpy(&data->sensor_data[0], &data->buf[3], 3);
 
-	iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
 					   iio_get_time_ns(indio_dev));
 
 out:
@@ -2523,23 +2538,24 @@ static irqreturn_t bmp180_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct bmp280_data *data = iio_priv(indio_dev);
-	int ret, chan_value;
+	int ret, comp_temp, comp_press, offset;
 
 	guard(mutex)(&data->lock);
 
-	ret = bmp180_read_temp(data, &chan_value);
+	ret = bmp180_read_temp(data, &comp_temp);
 	if (ret)
 		goto out;
 
-	data->sensor_data[1] = chan_value;
 
-	ret = bmp180_read_press(data, &chan_value);
+	ret = bmp180_read_press(data, &comp_press);
 	if (ret)
 		goto out;
 
-	data->sensor_data[0] = chan_value;
+	memcpy(&data->buffer.buf[offset], &comp_press, sizeof(s32));
+	offset += sizeof(s32);
+	memcpy(&data->buffer.buf[offset], &comp_temp, sizeof(s32));
 
-	iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
 					   iio_get_time_ns(indio_dev));
 
 out:
diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
index a9f220c1f77a..b0c26f55c6af 100644
--- a/drivers/iio/pressure/bmp280.h
+++ b/drivers/iio/pressure/bmp280.h
@@ -419,7 +419,10 @@ struct bmp280_data {
 	 * Data to push to userspace triggered buffer. Up to 3 channels and
 	 * s64 timestamp, aligned.
 	 */
-	s32 sensor_data[6] __aligned(8);
+	struct {
+		u8 buf[12];
+		aligned_s64 ts;
+	} buffer;
 
 	/*
 	 * DMA (thus cache coherency maintenance) may require the
-- 
2.25.1