iio:st_sensors: remove buffer allocation at each buffer enable

This patch is removing the buffer allocation at each buffer enable.
We just allocate enough memory in the main structure during probe
to cover maximum size needed (that anyway is pretty small) [16bytes].

Signed-off-by: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/st_accel_buffer.c

@@ -31,17 +31,11 @@ int st_accel_trig_set_state(struct iio_trigger *trig, bool state)
 
 static int st_accel_buffer_postenable(struct iio_dev *indio_dev)
 {
-	struct st_sensor_data *adata = iio_priv(indio_dev);
 	int err;
 
-	adata->buffer_data = kmalloc(indio_dev->scan_bytes,
-				     GFP_DMA | GFP_KERNEL);
-	if (!adata->buffer_data)
-		return -ENOMEM;
-
 	err = iio_triggered_buffer_postenable(indio_dev);
 	if (err < 0)
-		goto st_accel_free_buffer;
+		return err;
 
 	err = st_sensors_set_axis_enable(indio_dev,
 					 (u8)indio_dev->active_scan_mask[0]);
@@ -58,14 +52,11 @@ st_accel_buffer_enable_all_axis:
 	st_sensors_set_axis_enable(indio_dev, ST_SENSORS_ENABLE_ALL_AXIS);
 st_accel_buffer_predisable:
 	iio_triggered_buffer_predisable(indio_dev);
-st_accel_free_buffer:
-	kfree(adata->buffer_data);
 	return err;
 }
 
 static int st_accel_buffer_predisable(struct iio_dev *indio_dev)
 {
-	struct st_sensor_data *adata = iio_priv(indio_dev);
 	int err, err2;
 
 	err = st_sensors_set_enable(indio_dev, false);
@@ -79,7 +70,6 @@ st_accel_buffer_predisable:
 	if (!err)
 		err = err2;
 
-	kfree(adata->buffer_data);
 	return err;
 }