linux-kernel - [PATCH v2] iio: proximity: srf08: use stack allocated scan buffer

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Message-Id: <20250721-iio-use-more-iio_declare_buffer_with_ts-6-v2-1-8b66e5b4e75a@baylibre.com>
Date: Mon, 21 Jul 2025 17:21:08 -0500
From: David Lechner <dlechner@...libre.com>
To: Andreas Klinger <ak@...klinger.de>, Jonathan Cameron <jic23@...nel.org>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 David Lechner <dlechner@...libre.com>
Subject: [PATCH v2] iio: proximity: srf08: use stack allocated scan buffer

Use a stack allocated scan struct in srf08_trigger_handler(). Since the
scan buffer isn't used outside of this function and doesn't need to be
DMA-safe, it doesn't need to be in struct srf08_data. We can also
eliminate an extra local variable for the return value of
srf08_read_ranging() by using scan.chan directly.

Reviewed-by: Andreas Klinger <ak@...klinger.de>
Signed-off-by: David Lechner <dlechner@...libre.com>
---
Changes in v2:
- Zero-init the scan struct to avoid leaking uninitialized stack to userspace.
- Link to v1: https://lore.kernel.org/r/20250711-iio-use-more-iio_declare_buffer_with_ts-6-v1-1-25c70b990d6c@baylibre.com
---
 drivers/iio/proximity/srf08.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/iio/proximity/srf08.c b/drivers/iio/proximity/srf08.c
index 6e32fdfd161b93a5624f757d5b7de579415b1055..d7e4cc48cfbf700c7828235de99a66324767316a 100644
--- a/drivers/iio/proximity/srf08.c
+++ b/drivers/iio/proximity/srf08.c
@@ -63,12 +63,6 @@ struct srf08_data {
 	int			range_mm;
 	struct mutex		lock;
 
-	/* Ensure timestamp is naturally aligned */
-	struct {
-		s16 chan;
-		aligned_s64 timestamp;
-	} scan;
-
 	/* Sensor-Type */
 	enum srf08_sensor_type	sensor_type;
 
@@ -182,16 +176,18 @@ static irqreturn_t srf08_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct srf08_data *data = iio_priv(indio_dev);
-	s16 sensor_data;
+	struct {
+		s16 chan;
+		aligned_s64 timestamp;
+	} scan = { };
 
-	sensor_data = srf08_read_ranging(data);
-	if (sensor_data < 0)
+	scan.chan = srf08_read_ranging(data);
+	if (scan.chan < 0)
 		goto err;
 
 	mutex_lock(&data->lock);
 
-	data->scan.chan = sensor_data;
-	iio_push_to_buffers_with_ts(indio_dev, &data->scan, sizeof(data->scan),
+	iio_push_to_buffers_with_ts(indio_dev, &scan, sizeof(scan),
 				    pf->timestamp);
 
 	mutex_unlock(&data->lock);

---
base-commit: cd2731444ee4e35db76f4fb587f12d327eec5446
change-id: 20250711-iio-use-more-iio_declare_buffer_with_ts-6-6ffc8e99552d

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