linux-kernel - [PATCH v2] iio: proximity: isl29501: fix buffered read on big-endian systems

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Message-Id: <20250722-iio-use-more-iio_declare_buffer_with_ts-7-v2-1-d3ebeb001ed3@baylibre.com>
Date: Tue, 22 Jul 2025 15:54:21 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Mathieu Othacehe <othacehe@....org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 David Lechner <dlechner@...libre.com>
Subject: [PATCH v2] iio: proximity: isl29501: fix buffered read on
 big-endian systems

Fix passing a u32 value as a u16 buffer scan item. This works on little-
endian systems, but not on big-endian systems.

A new local variable is introduced for getting the register value and
the array is changed to a struct to make the data layout more explicit
rather than just changing the type and having to recalculate the proper
length needed for the timestamp.

Fixes: 1c28799257bc ("iio: light: isl29501: Add support for the ISL29501 ToF sensor.")
Signed-off-by: David Lechner <dlechner@...libre.com>
---
Changes in v2:
- Use u16 to match channel scan_type and introduce new local u32 variable
  for getting the register value.
- Reword subject and commit message since we now consider this a bug fix.
- Fix not zero-initializing the new struct.
- Link to v1: https://lore.kernel.org/r/20250711-iio-use-more-iio_declare_buffer_with_ts-7-v1-1-a3f253ac2e4a@baylibre.com
---
 drivers/iio/proximity/isl29501.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/proximity/isl29501.c b/drivers/iio/proximity/isl29501.c
index d1510fe2405088adc0998e28aa9f36e0186fafae..f69db6f2f380313b8444ee21399ee3a9faed6f04 100644
--- a/drivers/iio/proximity/isl29501.c
+++ b/drivers/iio/proximity/isl29501.c
@@ -938,12 +938,18 @@ static irqreturn_t isl29501_trigger_handler(int irq, void *p)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct isl29501_private *isl29501 = iio_priv(indio_dev);
 	const unsigned long *active_mask = indio_dev->active_scan_mask;
-	u32 buffer[4] __aligned(8) = {}; /* 1x16-bit + naturally aligned ts */
-
-	if (test_bit(ISL29501_DISTANCE_SCAN_INDEX, active_mask))
-		isl29501_register_read(isl29501, REG_DISTANCE, buffer);
+	u32 value;
+	struct {
+		u16 data;
+		aligned_s64 ts;
+	} scan = { };
+
+	if (test_bit(ISL29501_DISTANCE_SCAN_INDEX, active_mask)) {
+		isl29501_register_read(isl29501, REG_DISTANCE, &value);
+		scan.data = value;
+	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buffer, pf->timestamp);
+	iio_push_to_buffers_with_timestamp(indio_dev, &scan, pf->timestamp);
 	iio_trigger_notify_done(indio_dev->trig);
 
 	return IRQ_HANDLED;

---
base-commit: cd2731444ee4e35db76f4fb587f12d327eec5446
change-id: 20250711-iio-use-more-iio_declare_buffer_with_ts-7-880ddf1d3070

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