[PATCH] iio: ad_sigma_delta: Don't put SPI transfer buffer on the stack

[Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>]

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

Use a heap allocated memory for the SPI transfer buffer. Using stack memory
will not work on some architectures when using DMA.

Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---

Note: this doesn't need a stable/fixes tag. It's more of an enhancement.

 drivers/iio/adc/ad_sigma_delta.c       | 22 +++++++++++-----------
 include/linux/iio/adc/ad_sigma_delta.h |  3 ++-
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index af6cbc683214..02d9049b9218 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -58,7 +58,7 @@ EXPORT_SYMBOL_GPL(ad_sd_set_comm);
 int ad_sd_write_reg(struct ad_sigma_delta *sigma_delta, unsigned int reg,
 	unsigned int size, unsigned int val)
 {
-	uint8_t *data = sigma_delta->data;
+	uint8_t *data = sigma_delta->reg_data;
 	struct spi_transfer t = {
 		.tx_buf		= data,
 		.len		= size + 1,
@@ -102,7 +102,7 @@ EXPORT_SYMBOL_GPL(ad_sd_write_reg);
 static int ad_sd_read_reg_raw(struct ad_sigma_delta *sigma_delta,
 	unsigned int reg, unsigned int size, uint8_t *val)
 {
-	uint8_t *data = sigma_delta->data;
+	uint8_t *data = sigma_delta->reg_data;
 	int ret;
 	struct spi_transfer t[] = {
 		{
@@ -148,24 +148,24 @@ int ad_sd_read_reg(struct ad_sigma_delta *sigma_delta,
 {
 	int ret;
 
-	ret = ad_sd_read_reg_raw(sigma_delta, reg, size, sigma_delta->data);
+	ret = ad_sd_read_reg_raw(sigma_delta, reg, size, sigma_delta->reg_data);
 	if (ret < 0)
 		goto out;
 
 	switch (size) {
 	case 4:
-		*val = get_unaligned_be32(sigma_delta->data);
+		*val = get_unaligned_be32(sigma_delta->reg_data);
 		break;
 	case 3:
-		*val = (sigma_delta->data[0] << 16) |
-			(sigma_delta->data[1] << 8) |
-			sigma_delta->data[2];
+		*val = (sigma_delta->reg_data[0] << 16) |
+			(sigma_delta->reg_data[1] << 8) |
+			sigma_delta->reg_data[2];
 		break;
 	case 2:
-		*val = get_unaligned_be16(sigma_delta->data);
+		*val = get_unaligned_be16(sigma_delta->reg_data);
 		break;
 	case 1:
-		*val = sigma_delta->data[0];
+		*val = sigma_delta->reg_data[0];
 		break;
 	default:
 		ret = -EINVAL;
@@ -403,12 +403,12 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
+	uint8_t *data = sigma_delta->buf_data;
 	unsigned int reg_size;
 	unsigned int data_reg;
-	uint8_t data[16];
 	int ret;
 
-	memset(data, 0x00, 16);
+	memset(sigma_delta->buf_data, 0x00, sizeof(sigma_delta->buf_data));
 
 	reg_size = indio_dev->channels[0].scan_type.realbits +
 			indio_dev->channels[0].scan_type.shift;
diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h
index 6e9fb1932dde..fb77b2ebe498 100644
--- a/include/linux/iio/adc/ad_sigma_delta.h
+++ b/include/linux/iio/adc/ad_sigma_delta.h
@@ -79,7 +79,8 @@ struct ad_sigma_delta {
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
 	 */
-	uint8_t				data[4] ____cacheline_aligned;
+	uint8_t				reg_data[4] ____cacheline_aligned;
+	uint8_t				buf_data[16];
 };
 
 static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd,
-- 
2.17.1