linux-kernel - [PATCH v2 5/6] iio: accel: sca3300: use IIO_DECLARE_BUFFER_WITH

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Message-Id: <20250422-iio-introduce-iio_declare_buffer_with_ts-v2-5-3fd36475c706@baylibre.com>
Date: Tue, 22 Apr 2025 17:07:50 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Eugen Hristev <eugen.hristev@...aro.org>, 
 Nicolas Ferre <nicolas.ferre@...rochip.com>, 
 Alexandre Belloni <alexandre.belloni@...tlin.com>, 
 Claudiu Beznea <claudiu.beznea@...on.dev>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2 5/6] iio: accel: sca3300: use IIO_DECLARE_BUFFER_WITH_TS

Use IIO_DECLARE_BUFFER_WITH_TS to declare the buffer that gets used with
iio_push_to_buffers_with_ts(). This makes the code a bit easier to read
and understand.

Signed-off-by: David Lechner <dlechner@...libre.com>
---
This is an alternative to [1]. Also, this serves as a test to see if we
can get a rule of thumb to decide how much is too much to put on the
stack vs. needing to put the buffer in a static struct. SCA3300_SCAN_MAX
is 7, so this add a bit over 64 bytes to the stack, make the stack now
roughly double what it was before.

[1]: https://lore.kernel.org/linux-iio/20250418-iio-prefer-aligned_s64-timestamp-v1-1-4c6080710516@baylibre.com/
---
 drivers/iio/accel/sca3300.c | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/drivers/iio/accel/sca3300.c b/drivers/iio/accel/sca3300.c
index 1132bbaba75bcca525fac2f3e19f63546380fd4f..67416a406e2f43e4e417210410904d44c93111d2 100644
--- a/drivers/iio/accel/sca3300.c
+++ b/drivers/iio/accel/sca3300.c
@@ -58,15 +58,6 @@ enum sca3300_scan_indexes {
 	SCA3300_SCAN_MAX
 };
 
-/*
- * Buffer size max case:
- * Three accel channels, two bytes per channel.
- * Temperature channel, two bytes.
- * Three incli channels, two bytes per channel.
- * Timestamp channel, eight bytes.
- */
-#define SCA3300_MAX_BUFFER_SIZE (ALIGN(sizeof(s16) * SCA3300_SCAN_MAX, sizeof(s64)) + sizeof(s64))
-
 #define SCA3300_ACCEL_CHANNEL(index, reg, axis) {			\
 	.type = IIO_ACCEL,						\
 	.address = reg,							\
@@ -193,9 +184,6 @@ struct sca3300_chip_info {
  * @spi: SPI device structure
  * @lock: Data buffer lock
  * @chip: Sensor chip specific information
- * @buffer: Triggered buffer:
- *          -SCA3300: 4 channel 16-bit data + 64-bit timestamp
- *          -SCL3300: 7 channel 16-bit data + 64-bit timestamp
  * @txbuf: Transmit buffer
  * @rxbuf: Receive buffer
  */
@@ -203,7 +191,6 @@ struct sca3300_data {
 	struct spi_device *spi;
 	struct mutex lock;
 	const struct sca3300_chip_info *chip;
-	u8 buffer[SCA3300_MAX_BUFFER_SIZE] __aligned(sizeof(s64));
 	u8 txbuf[4] __aligned(IIO_DMA_MINALIGN);
 	u8 rxbuf[4];
 };
@@ -492,7 +479,7 @@ static irqreturn_t sca3300_trigger_handler(int irq, void *p)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct sca3300_data *data = iio_priv(indio_dev);
 	int bit, ret, val, i = 0;
-	s16 *channels = (s16 *)data->buffer;
+	IIO_DECLARE_BUFFER_WITH_TS(s16, channels, SCA3300_SCAN_MAX);
 
 	iio_for_each_active_channel(indio_dev, bit) {
 		ret = sca3300_read_reg(data, indio_dev->channels[bit].address, &val);
@@ -505,8 +492,7 @@ static irqreturn_t sca3300_trigger_handler(int irq, void *p)
 		channels[i++] = val;
 	}
 
-	iio_push_to_buffers_with_ts(indio_dev, data->buffer,
-				    sizeof(data->buffer),
+	iio_push_to_buffers_with_ts(indio_dev, channels, sizeof(channels),
 				    iio_get_time_ns(indio_dev));
 out:
 	iio_trigger_notify_done(indio_dev->trig);

-- 
2.43.0