linux-kernel - [PATCH] iio: proximity: sx9500: use stack allocated buffer for scan data

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Message-Id: <20250711-iio-use-more-iio_declare_buffer_with_ts-4-v1-1-1a1e521cf747@baylibre.com>
Date: Fri, 11 Jul 2025 10:47:57 -0500
From: David Lechner <dlechner@...libre.com>
To: 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] iio: proximity: sx9500: use stack allocated buffer for
 scan data

Use IIO_DECLARE_BUFFER_WITH_TS() to declare a stack allocated buffer
in sx9500_trigger_handler(). Since the scan buffer isn't used outside
of this function, it doesn't need to be in struct sx9500_data.

By always allocating enough space for the maximum number of channels,
we can avoid having to reallocate the buffer each time buffered reads
are enabled.

Signed-off-by: David Lechner <dlechner@...libre.com>
---
 drivers/iio/proximity/sx9500.c | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/drivers/iio/proximity/sx9500.c b/drivers/iio/proximity/sx9500.c
index 05844f17a15f6980ab7d55536e5fecfc5e4fe8c0..373e60b5c92fcd508af6420fff8067794d429a1c 100644
--- a/drivers/iio/proximity/sx9500.c
+++ b/drivers/iio/proximity/sx9500.c
@@ -88,7 +88,6 @@ struct sx9500_data {
 	bool prox_stat[SX9500_NUM_CHANNELS];
 	bool event_enabled[SX9500_NUM_CHANNELS];
 	bool trigger_enabled;
-	u16 *buffer;
 	/* Remember enabled channels and sample rate during suspend. */
 	unsigned int suspend_ctrl0;
 	struct completion completion;
@@ -578,22 +577,6 @@ static int sx9500_write_event_config(struct iio_dev *indio_dev,
 	return ret;
 }
 
-static int sx9500_update_scan_mode(struct iio_dev *indio_dev,
-				   const unsigned long *scan_mask)
-{
-	struct sx9500_data *data = iio_priv(indio_dev);
-
-	mutex_lock(&data->mutex);
-	kfree(data->buffer);
-	data->buffer = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
-	mutex_unlock(&data->mutex);
-
-	if (data->buffer == NULL)
-		return -ENOMEM;
-
-	return 0;
-}
-
 static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
 	"2.500000 3.333333 5 6.666666 8.333333 11.111111 16.666666 33.333333");
 
@@ -612,7 +595,6 @@ static const struct iio_info sx9500_info = {
 	.write_raw = &sx9500_write_raw,
 	.read_event_config = &sx9500_read_event_config,
 	.write_event_config = &sx9500_write_event_config,
-	.update_scan_mode = &sx9500_update_scan_mode,
 };
 
 static int sx9500_set_trigger_state(struct iio_trigger *trig,
@@ -645,6 +627,7 @@ static const struct iio_trigger_ops sx9500_trigger_ops = {
 
 static irqreturn_t sx9500_trigger_handler(int irq, void *private)
 {
+	IIO_DECLARE_BUFFER_WITH_TS(u16, buffer, SX9500_NUM_CHANNELS);
 	struct iio_poll_func *pf = private;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct sx9500_data *data = iio_priv(indio_dev);
@@ -658,10 +641,10 @@ static irqreturn_t sx9500_trigger_handler(int irq, void *private)
 		if (ret < 0)
 			goto out;
 
-		data->buffer[i++] = val;
+		buffer[i++] = val;
 	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
+	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
 					   iio_get_time_ns(indio_dev));
 
 out:
@@ -984,7 +967,6 @@ static void sx9500_remove(struct i2c_client *client)
 	iio_triggered_buffer_cleanup(indio_dev);
 	if (client->irq > 0)
 		iio_trigger_unregister(data->trig);
-	kfree(data->buffer);
 }
 
 static int sx9500_suspend(struct device *dev)

---
base-commit: f8f559752d573a051a984adda8d2d1464f92f954
change-id: 20250711-iio-use-more-iio_declare_buffer_with_ts-4-66ddcde563fe

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