[PATCH v2] iio: st_sensors: drop temporary kmalloc buffer and reuse buffer_data

[Sanjay Chitroda]

From: Sanjay Chitroda <sanjayembeddedse@xxxxxxxxx>

Replace the per-call kmalloc() scratch buffer with the statically allocated
buffer_data[] field present in struct st_sensor_data. The existing buffer
is DMA-aligned and sufficiently sized for all channel widths, so using it
avoids unnecessary dynamic memory allocation on each read.

This simplifies the code, removes redundent code and allocation.
No functional change intended.

Signed-off-by: Sanjay Chitroda <sanjayembeddedse@xxxxxxxxx>
---
Changes in v2:
- split series to individual patch
- address review comment from David Lechner and reuse exising buffer instead of allocation
- Link to v1 https://lore.kernel.org/all/20260310200513.2162018-4-sanjayembedded@xxxxxxxxx/
---
 drivers/iio/common/st_sensors/st_sensors_core.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
index dac593be5695..488e2bf6d117 100644
--- a/drivers/iio/common/st_sensors/st_sensors_core.c
+++ b/drivers/iio/common/st_sensors/st_sensors_core.c
@@ -495,20 +495,17 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev,
 				     struct iio_chan_spec const *ch, int *data)
 {
 	int err;
-	u8 *outdata;
 	struct st_sensor_data *sdata = iio_priv(indio_dev);
 	unsigned int byte_for_channel;
 
 	byte_for_channel = DIV_ROUND_UP(ch->scan_type.realbits +
 					ch->scan_type.shift, 8);
-	outdata = kmalloc(byte_for_channel, GFP_DMA | GFP_KERNEL);
-	if (!outdata)
-		return -ENOMEM;
+	u8 *outdata = (u8 *)sdata->buffer_data;
 
 	err = regmap_bulk_read(sdata->regmap, ch->address,
 			       outdata, byte_for_channel);
 	if (err < 0)
-		goto st_sensors_free_memory;
+		return err;
 
 	if (byte_for_channel == 1)
 		*data = (s8)*outdata;
@@ -517,10 +514,7 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev,
 	else if (byte_for_channel == 3)
 		*data = (s32)sign_extend32(get_unaligned_le24(outdata), 23);
 
-st_sensors_free_memory:
-	kfree(outdata);
-
-	return err;
+	return 0;
 }
 
 int st_sensors_read_info_raw(struct iio_dev *indio_dev,
-- 
2.34.1