linux-kernel - [PATCH] iio: amplifiers: ada4250: use DMA-safe memory for regmap_bulk

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Message-Id: <20250418-iio-amplifiers-ada4250-simplify-data-buffer-in-init-v1-1-7e7bd6dad423@baylibre.com>
Date: Fri, 18 Apr 2025 13:16:13 -0500
From: David Lechner <dlechner@...libre.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>, 
 Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 David Lechner <dlechner@...libre.com>
Subject: [PATCH] iio: amplifiers: ada4250: use DMA-safe memory for
 regmap_bulk_read()

Use DMA-safe memory instead of stack-allocated memory for the call to
regmap_bulk_read() in the ada4250_init() function as this could be used
directly by a SPI controller.

Also remove unnecessary use of get_unaligned_le16() and explicitly
include linux/types.h e.g. for __le16 while we are fixing this up.

Fixes: 28b4c30bfa5f ("iio: amplifiers: ada4250: add support for ADA4250")
Signed-off-by: David Lechner <dlechner@...libre.com>
---
 drivers/iio/amplifiers/ada4250.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/amplifiers/ada4250.c b/drivers/iio/amplifiers/ada4250.c
index 74f8429d652b17b4d1f38366e23ce6a2b3e9b218..f81438460aa51ce30f8f605c60ee5be5c8c251d3 100644
--- a/drivers/iio/amplifiers/ada4250.c
+++ b/drivers/iio/amplifiers/ada4250.c
@@ -13,8 +13,7 @@
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/spi/spi.h>
-
-#include <linux/unaligned.h>
+#include <linux/types.h>
 
 /* ADA4250 Register Map */
 #define ADA4250_REG_GAIN_MUX        0x00
@@ -63,6 +62,7 @@ struct ada4250_state {
 	u8			gain;
 	int			offset_uv;
 	bool			refbuf_en;
+	__le16			reg_val_16 __aligned(IIO_DMA_MINALIGN);
 };
 
 /* ADA4250 Current Bias Source Settings: Disabled, Bandgap Reference, AVDD */
@@ -301,7 +301,6 @@ static int ada4250_init(struct ada4250_state *st)
 {
 	int ret;
 	u16 chip_id;
-	u8 data[2] __aligned(8) = {};
 	struct spi_device *spi = st->spi;
 
 	st->refbuf_en = device_property_read_bool(&spi->dev, "adi,refbuf-enable");
@@ -326,11 +325,12 @@ static int ada4250_init(struct ada4250_state *st)
 	if (ret)
 		return ret;
 
-	ret = regmap_bulk_read(st->regmap, ADA4250_REG_CHIP_ID, data, 2);
+	ret = regmap_bulk_read(st->regmap, ADA4250_REG_CHIP_ID, &st->reg_val_16,
+			       sizeof(st->reg_val_16));
 	if (ret)
 		return ret;
 
-	chip_id = get_unaligned_le16(data);
+	chip_id = le16_to_cpu(st->reg_val_16);
 
 	if (chip_id != ADA4250_CHIP_ID) {
 		dev_err(&spi->dev, "Invalid chip ID.\n");

---
base-commit: aff301f37e220970c2f301b5c65a8bfedf52058e
change-id: 20250418-iio-amplifiers-ada4250-simplify-data-buffer-in-init-93ebb1344295

Best regards,
-- 
David Lechner <dlechner@...libre.com>